Researchers have promised that the Perovskite solar cells (PSCs) soon be released as a commercial product in the next few years. It has become a hot topic among researchers because of its superior optoelectronic property. Ease device fabrication made this device keep it in limelight among other next-generation solar cells. Replacing the organic hole transport layer (HTL) in perovskite solar cells with inorganic p-type metal oxide materials is an effective way to improve the device's performance and stability. Nickel oxide (NiOx) is an ideal candidate for this special purpose but these metal oxides require special processing conditions like a vacuum, heat treatment, etc. This restricts perovskite solar cells from flexible devices. To overcome these problems, solution-processed NiOx has a variety of options that doesn’t require any special processing conditions. Sol-gel, Combustion, and Pre-synthesized nanoparticles (NPs) are the three different approaches of solution process thin film that have been adopted to prepare NiOx HTL for PSCs. Each technique has a unique advantage over one another but all these techniques have produced efficient NiOx HTL for PSCs are reported in this work. The efficient PSCs was fabricated at various processing temperature from room temperature (RT) to 400 °C using these techniques.
In the sol-gel process, the best efficient PSCs was achieved from the NiOx HTL at the processing temperature of 300 and 400 °C. To reduce the processing temperature of HTL, the combustion technique was deployed to produce efficient PSCs at 250 °C. Further reducing the processing temperature by the pre-synthesized NPs HTL deposited at RT where it performs well without any heat treatment. Also, the performance of low-temperature processed NiOx HTL was improved by various metal ion doping in NiOx. Extrinsic metal ion doping has been successfully incorporated into the NiOx and showed relatively better performance than the pristine NiOx device. Effects of heat treatment and metal ion doping in NiOx HTL for PSCs have been studied extensively using various material and device characterization techniques. The efficient device can be achieved at any processing temperature irrespective of perovskite composition. This kind of solution-processed approach can reduce the fabrication cost in large-scale commercial applications. It is believed that this work can provide a basic understanding and strategy to develop highly efficient NiOx HTL in PSCs.

Dedication 1
Acknowledgments III
Abstract V
Table of Contents VII
List of Figures IX
List of Tables XIII
Chapter 1. Introduction to Perovskite Solar Cells and Hole Transport Layer 1
1.1 Introduction 1
1.2 Perovskite solar cells (PSCs) 4
1.3 Perovskite Intrinsic Layer 7
1.3.1 Perovskite crystal structure 7
1.3.2 Methylammonium Lead Iodide Perovskite 8
1.3.3 Synthesis methods and additives 8
1.3.4 Stability for perovskite materials 10
1.4 Electron transport layer 11
1.5 Hole transport layer 13
1.5.1 Role of hole transport layer in PSCs 13
1.5.2 Electronic and Optoelectronic Properties of HTL 14
1.5.3 Design requirements of HTL in PSCs 16
1.6 Nickel oxide as efficient hole transport layer 17
1.6.1 Properties of Nickel oxide 17
1.6.2 Advantages and disadvantages of NiOx as HTL 19
1.7 Purpose of the study 20
Chapter 2. Experimental techniques 23
2.1 Spin coating technique 23
2.2 Pre/Post-Deposition treatment 24
2.3 Thermal evaporation 25
2.4 X-Ray diffraction 26
2.5 X-ray photoelectron spectroscopy (XPS) 27
2.6 Field Emission Scanning Electron Microscopy (FESEM) 28
2.7 Atomic force microscopy (AFM) 30
2.8 Ultraviolet-visible (UV-Vis) spectroscopy 31
2.9 Steady-state Photoluminescence & Time-Resolved Photoluminescence (TRPL) 32
2.10 Device fabrication 34
2.11 Device characterization 36
2.11.1 Current-Voltage (IV) measurement 36
2.11.2 Quantum Efficiency 39
2.11.3 Electrochemical impedance spectroscopy (EIS) 41
Chapter 3. Sol-gel processed nickel oxide thin films as a hole transport layer for perovskite solar cells 43
3.1 Introduction 43
3.2 NiOx thin film using nickel acetylacetonate (Ni-acac) 44
3.2.1 Experimental Details 44
3.2.2 Results and Discussion 45
3.2.3 Conclusion 58
3.3 NiOx thin film using nickel acetate tetrahydrate (Ni-ac) 59
3.3.1 Experimental Details 59
3.3.2 Results and Discussion 60
3.3.3 Conclusion 73
3.4 Summary 73
Chapter 4. Combustion processed nickel oxide thin films as a hole transport layer for perovskite solar cells 75
4.1 Introduction 75
4.2 Experimental Details 76
4.3 Results and Discussion 77
4.4 Conclusion 90
Chapter 5. Sintered nanoparticles-based nickel oxide thin films as a hole transport layer for perovskite solar cells 93
5.1 Introduction 93
5.2 Experimental details 94
5.3 Results and Discussion 95
5.4 Conclusion 114
Chapter 6. Summary 115
References 119

[1] Fossil Fuels | EESI, (n.d.). https://www.eesi.org/topics/fossil-fuels/description (accessed March 3, 2021).
[2] What is Generation Capacity? | Department of Energy, (n.d.). https://www.energy.gov/ne/articles/what-generation-capacity (accessed March 3, 2021).
[3] Dangers and Effects of Nuclear Waste Disposal - Conserve Energy Future, (n.d.). https://www.conserve-energy-future.com/dangers-and-effects-of-nuclear-waste-disposal.php (accessed March 3, 2021).
[4] Infographic: The World’s Projected Energy Mix, 2018-2040, (n.d.). https://www.visualcapitalist.com/the-worlds-projected-energy-mix-2018-2040/ (accessed March 3, 2021).
[5] Renewable Energy | Types, Forms & Sources | EDF, (n.d.). https://www.edfenergy.com/for-home/energywise/renewable-energy-sources (accessed March 3, 2021).
[6] Solar’s Future is Insanely Cheap (2020) – Ramez Naam, (n.d.). https://rameznaam.com/2020/05/14/solars-future-is-insanely-cheap-2020/ (accessed March 3, 2021).
[7] Best Research-Cell Efficiency Chart | Photovoltaic Research | NREL, (n.d.). https://www.nrel.gov/pv/cell-efficiency.html (accessed July 10, 2020).
[8] A. Kojima, K. Teshima, T. Miyasaka, Y. Shirai, Novel Photoelectrochemical Cell with Mesoscopic Electrodes Sensitized by Lead-Halide Compounds (2), ECS Meet. Abstr. MA2006-02 (2006) 397. https://doi.org/10.1149/ma2006-02/7/397.
[9] A. Kojima, K. Teshima, Y. Shirai, T. Miyasaka, Organometal halide perovskites as visible-light sensitizers for photovoltaic cells, J. Am. Chem. Soc. 131 (2009) 6050–6051. https://doi.org/10.1021/ja809598r.
[10] M.M. Lee, J. Teuscher, T. Miyasaka, T.N. Murakami, H.J. Snaith, Efficient hybrid solar cells based on meso-superstructured organometal halide perovskites, Science (80-. ). 338 (2012) 643–647. https://doi.org/10.1126/science.1228604.
[11] H.S. Kim, C.R. Lee, J.H. Im, K.B. Lee, T. Moehl, A. Marchioro, S.J. Moon, R. Humphry-Baker, J.H. Yum, J.E. Moser, M. Grätzel, N.G. Park, Lead iodide perovskite sensitized all-solid-state submicron thin film mesoscopic solar cell with efficiency exceeding 9%, Sci. Rep. 2 (2012) 1–7. https://doi.org/10.1038/srep00591.
[12] T. Liu, K. Chen, Q. Hu, R. Zhu, Q. Gong, Inverted Perovskite Solar Cells: Progresses and Perspectives, Adv. Energy Mater. 6 (2016) 1600457. https://doi.org/10.1002/aenm.201600457.
[13] A. Marchioro, J. Teuscher, D. Friedrich, M. Kunst, R. Van De Krol, T. Moehl, M. Grätzel, J.E. Moser, Unravelling the mechanism of photoinduced charge transfer processes in lead iodide perovskite solar cells, Nat. Photonics. 8 (2014) 250–255. https://doi.org/10.1038/nphoton.2013.374.
[14] G. Yang, H. Tao, P. Qin, W. Ke, G. Fang, Recent progress in electron transport layers for efficient perovskite solar cells, J. Mater. Chem. A. 4 (2016) 3970–3990. https://doi.org/10.1039/c5ta09011c.
[15] H.J. Snaith, A. Abate, J.M. Ball, G.E. Eperon, T. Leijtens, N.K. Noel, S.D. Stranks, J.T.W. Wang, K. Wojciechowski, W. Zhang, Anomalous hysteresis in perovskite solar cells, J. Phys. Chem. Lett. 5 (2014) 1511–1515. https://doi.org/10.1021/jz500113x.
[16] Z. Li, C. Xiao, Y. Yang, S.P. Harvey, D.H. Kim, J.A. Christians, M. Yang, P. Schulz, S.U. Nanayakkara, C.S. Jiang, J.M. Luther, J.J. Berry, M.C. Beard, M.M. Al-Jassim, K. Zhu, Extrinsic ion migration in perovskite solar cells, Energy Environ. Sci. 10 (2017) 1234–1242. https://doi.org/10.1039/c7ee00358g.
[17] J. Wei, Y. Zhao, H. Li, G. Li, J. Pan, D. Xu, Q. Zhao, D. Yu, Hysteresis analysis based on the ferroelectric effect in hybrid perovskite solar cells, J. Phys. Chem. Lett. 5 (2014) 3937–3945. https://doi.org/10.1021/jz502111u.
[18] T. Zhang, H. Chen, Y. Bai, S. Xiao, L. Zhu, C. Hu, Q. Xue, S. Yang, Understanding the relationship between ion migration and the anomalous hysteresis in high-efficiency perovskite solar cells: A fresh perspective from halide substitution, Nano Energy. 26 (2016) 620–630. https://doi.org/10.1016/j.nanoen.2016.05.052.
[19] C. Motta, F. El-Mellouhi, S. Kais, N. Tabet, F. Alharbi, S. Sanvito, Revealing the role of organic cations in hybrid halide perovskite CH3 NH3PbI3, Nat. Commun. 6 (2015) 1–7. https://doi.org/10.1038/ncomms8026.
[20] K. Wu, A. Bera, C. Ma, Y. Du, Y. Yang, L. Li, T. Wu, Temperature-dependent excitonic photoluminescence of hybrid organometal halide perovskite films, Phys. Chem. Chem. Phys. 16 (2014) 22476–22481. https://doi.org/10.1039/c4cp03573a.
[21] S. Tao, I. Schmidt, G. Brocks, J. Jiang, I. Tranca, K. Meerholz, S. Olthof, Absolute energy level positions in tin- and lead-based halide perovskites, Nat. Commun. 10 (2019) 1–10. https://doi.org/10.1038/s41467-019-10468-7.
[22] D.T. Moore, H. Sai, K.W. Tan, D.M. Smilgies, W. Zhang, H.J. Snaith, U. Wiesner, L.A. Estroff, Crystallization kinetics of organic-inorganic trihalide perovskites and the role of the lead anion in crystal growth, J. Am. Chem. Soc. 137 (2015) 2350–2358. https://doi.org/10.1021/ja512117e.
[23] T. Bin Song, Q. Chen, H. Zhou, C. Jiang, H.H. Wang, Y.M. Yang, Y. Liu, J. You, Y. Yang, Perovskite solar cells: Film formation and properties, J. Mater. Chem. A. 3 (2015) 9032–9050. https://doi.org/10.1039/c4ta05246c.
[24] Y. Zhou, M. Yang, W. Wu, A.L. Vasiliev, K. Zhu, N.P. Padture, Room-temperature crystallization of hybrid-perovskite thin films via solvent-solvent extraction for high-performance solar cells, J. Mater. Chem. A. 3 (2015) 8178–8184. https://doi.org/10.1039/c5ta00477b.
[25] J. Burschka, N. Pellet, S.J. Moon, R. Humphry-Baker, P. Gao, M.K. Nazeeruddin, M. Grätzel, Sequential deposition as a route to high-performance perovskite-sensitized solar cells, Nature. 499 (2013) 316–319. https://doi.org/10.1038/nature12340.
[26] J.W. Lee, H.S. Kim, N.G. Park, Lewis Acid-Base Adduct Approach for High Efficiency Perovskite Solar Cells, Acc. Chem. Res. 49 (2016) 311–319. https://doi.org/10.1021/acs.accounts.5b00440.
[27] Z. Liu, J. Hu, H. Jiao, L. Li, G. Zheng, Y. Chen, Y. Huang, Q. Zhang, C. Shen, Q. Chen, H. Zhou, Chemical Reduction of Intrinsic Defects in Thicker Heterojunction Planar Perovskite Solar Cells, Adv. Mater. 29 (2017) 1606774. https://doi.org/10.1002/adma.201606774.
[28] Z. Zhou, Z. Wang, Y. Zhou, S. Pang, D. Wang, H. Xu, Z. Liu, N.P. Padture, G. Cui, Methylamine-Gas-Induced Defect-Healing Behavior of CH 3 NH 3 PbI 3 Thin Films for Perovskite Solar Cells, Angew. Chemie. 127 (2015) 9841–9845. https://doi.org/10.1002/ange.201504379.
[29] Y. Zhao, J. Wei, H. Li, Y. Yan, W. Zhou, D. Yu, Q. Zhao, A polymer scaffold for self-healing perovskite solar cells, Nat. Commun. 7 (2016) 1–9. https://doi.org/10.1038/ncomms10228.
[30] L. Zuo, H. Guo, D.W. DeQuilettes, S. Jariwala, N. De Marco, S. Dong, R. DeBlock, D.S. Ginger, B. Dunn, M. Wang, Y. Yang, Polymer-modified halide perovskite films for efficient and stable planar heterojunction solar cells, Sci. Adv. 3 (2017) e1700106. https://doi.org/10.1126/sciadv.1700106.
[31] Q. Chen, H. Zhou, T. Bin Song, S. Luo, Z. Hong, H.S. Duan, L. Dou, Y. Liu, Y. Yang, Controllable self-induced passivation of hybrid lead iodide perovskites toward high performance solar cells, Nano Lett. 14 (2014) 4158–4163. https://doi.org/10.1021/nl501838y.
[32] Q. Wang, B. Chen, Y. Liu, Y. Deng, Y. Bai, Q. Dong, J. Huang, Scaling behavior of moisture-induced grain degradation in polycrystalline hybrid perovskite thin films, Energy Environ. Sci. 10 (2017) 516–522. https://doi.org/10.1039/c6ee02941h.
[33] W. Huang, J.S. Manser, P. V. Kamat, S. Ptasinska, Evolution of Chemical Composition, Morphology, and Photovoltaic Efficiency of CH3NH3PbI3 Perovskite under Ambient Conditions, Chem. Mater. 28 (2016) 303–311. https://doi.org/10.1021/acs.chemmater.5b04122.
[34] B.J. Kim, D.H. Kim, S.L. Kwon, S.Y. Park, Z. Li, K. Zhu, H.S. Jung, Selective dissolution of halide perovskites as a step towards recycling solar cells, Nat. Commun. 7 (2016) 1–9. https://doi.org/10.1038/ncomms11735.
[35] C. Qin, T. Matsushima, T. Fujihara, W.J. Potscavage, C. Adachi, Degradation Mechanisms of Solution-Processed Planar Perovskite Solar Cells: Thermally Stimulated Current Measurement for Analysis of Carrier Traps, Adv. Mater. 28 (2016) 466–471. https://doi.org/10.1002/adma.201502610.
[36] B. Rivkin, P. Fassl, Q. Sun, A.D. Taylor, Z. Chen, Y. Vaynzof, Effect of Ion Migration-Induced Electrode Degradation on the Operational Stability of Perovskite Solar Cells, ACS Omega. 3 (2018) 10042–10047. https://doi.org/10.1021/acsomega.8b01626.
[37] S. Wang, Y. Jiang, E.J. Juarez-Perez, L.K. Ono, Y. Qi, Accelerated degradation of methylammonium lead iodide perovskites induced by exposure to iodine vapour, Nat. Energy. 2 (2017) 1–8. https://doi.org/10.1038/nenergy.2016.195.
[38] M.F. Mohamad Noh, C.H. Teh, R. Daik, E.L. Lim, C.C. Yap, M.A. Ibrahim, N. Ahmad Ludin, A.R. Bin Mohd Yusoff, J. Jang, M.A. Mat Teridi, The architecture of the electron transport layer for a perovskite solar cell, J. Mater. Chem. C. 6 (2018) 682–712. https://doi.org/10.1039/c7tc04649a.
[39] M. Salado, M. Oliva-Ramirez, S. Kazim, A.R. González-Elipe, S. Ahmad, 1-dimensional TiO2 nano-forests as photoanodes for efficient and stable perovskite solar cells fabrication, Nano Energy. 35 (2017) 215–222. https://doi.org/10.1016/j.nanoen.2017.03.034.
[40] Y. Bai, H. Yu, Z. Zhu, K. Jiang, T. Zhang, N. Zhao, S. Yang, H. Yan, High performance inverted structure perovskite solar cells based on a PCBM: Polystyrene blend electron transport layer, J. Mater. Chem. A. 3 (2015) 9098–9102. https://doi.org/10.1039/c4ta05309e.
[41] Y. Zhong, M. Hufnagel, M. Thelakkat, C. Li, S. Huettner, Role of PCBM in the Suppression of Hysteresis in Perovskite Solar Cells, Adv. Funct. Mater. 30 (2020) 1908920. https://doi.org/10.1002/adfm.201908920.
[42] W. Chen, Y. Shi, Y. Wang, X. Feng, A.B. Djurišić, H.Y. Woo, X. Guo, Z. He, N-type conjugated polymer as efficient electron transport layer for planar inverted perovskite solar cells with power conversion efficiency of 20.86%, Nano Energy. 68 (2020) 104363. https://doi.org/10.1016/j.nanoen.2019.104363.
[43] L. Calió, S. Kazim, M. Grätzel, S. Ahmad, Hole-Transport Materials for Perovskite Solar Cells, Angew. Chemie Int. Ed. 55 (2016) 14522–14545. https://doi.org/10.1002/anie.201601757.
[44] Z.H. Bakr, Q. Wali, A. Fakharuddin, L. Schmidt-Mende, T.M. Brown, R. Jose, Advances in hole transport materials engineering for stable and efficient perovskite solar cells, Nano Energy. 34 (2017) 271–305. https://doi.org/10.1016/j.nanoen.2017.02.025.
[45] W. Yan, S. Ye, Y. Li, W. Sun, H. Rao, Z. Liu, Z. Bian, C. Huang, Hole-Transporting Materials in Inverted Planar Perovskite Solar Cells, Adv. Energy Mater. 6 (2016) 1600474. https://doi.org/10.1002/aenm.201600474.
[46] C. Cetin, P. Chen, M. Hao, D. He, Y. Bai, M. Lyu, J.-H. Yun, L. Wang, Inorganic p-Type Semiconductors as Hole Conductor Building Blocks for Robust Perovskite Solar Cells, Adv. Sustain. Syst. 2 (2018) 1800032. https://doi.org/10.1002/adsu.201800032.
[47] K. Ellmer, Past achievements and future challenges in the development of optically transparent electrodes, Nat. Photonics. 6 (2012) 809–817. https://doi.org/10.1038/nphoton.2012.282.
[48] K.H.L. Zhang, K. Xi, M.G. Blamire, R.G. Egdell, P-type transparent conducting oxides, J. Phys. Condens. Matter. 28 (2016) 383002. https://doi.org/10.1088/0953-8984/28/38/383002.
[49] J.A. Christians, P. Schulz, J.S. Tinkham, T.H. Schloemer, S.P. Harvey, B.J. Tremolet De Villers, A. Sellinger, J.J. Berry, J.M. Luther, Tailored interfaces of unencapsulated perovskite solar cells for >1,000 hour operational stability, Nat. Energy. 3 (2018) 68–74. https://doi.org/10.1038/s41560-017-0067-y.
[50] E.J. Juarez-Perez, Z. Hawash, S.R. Raga, L.K. Ono, Y. Qi, Thermal degradation of CH3NH3PbI3 perovskite into NH3 and CH3I gases observed by coupled thermogravimetry-mass spectrometry analysis, Energy Environ. Sci. 9 (2016) 3406–3410. https://doi.org/10.1039/c6ee02016j.
[51] H. Sato, T. Minami, S. Takata, T. Yamada, Transparent conducting p-type NiO thin films prepared by magnetron sputtering, Thin Solid Films. 236 (1993) 27–31. https://doi.org/10.1016/0040-6090(93)90636-4.
[52] X. Yin, Y. Guo, H. Xie, W. Que, L.B. Kong, Nickel Oxide as Efficient Hole Transport Materials for Perovskite Solar Cells, Sol. RRL. 3 (2019) 1900001. https://doi.org/10.1002/solr.201900001.
[53] P. Qin, Q. He, D. Ouyang, G. Fang, W.C.H. Choy, G. Li, Transition metal oxides as hole-transporting materials in organic semiconductor and hybrid perovskite based solar cells, Sci. China Chem. 60 (2017) 472–489. https://doi.org/10.1007/s11426-016-9023-5.
[54] S. Uhlenbrock, C. Scharfschwerdt, M. Neumann, G. Illing, H.J. Freund, The influence of defects on the Ni 2p and O 1s XPS of NiO, J. Phys. Condens. Matter. 4 (1992) 7973–7978. https://doi.org/10.1088/0953-8984/4/40/009.
[55] B. Sasi, K.G. Gopchandran, Nanostructured mesoporous nickel oxide thin films, Nanotechnology. 18 (2007) 9. https://doi.org/10.1088/0957-4484/18/11/115613.
[56] Z. Zhu, Y. Bai, T. Zhang, Z. Liu, X. Long, Z. Wei, Z. Wang, L. Zhang, J. Wang, F. Yan, S. Yang, High-Performance Hole-Extraction Layer of Sol-Gel-Processed NiO Nanocrystals for Inverted Planar Perovskite Solar Cells, Angew. Chemie. 126 (2014) 12779–12783. https://doi.org/10.1002/ange.201405176.
[57] J.R. Manders, S.-W. Tsang, M.J. Hartel, T.-H. Lai, S. Chen, C.M. Amb, J.R. Reynolds, F. So, Solution-Processed Nickel Oxide Hole Transport Layers in High Efficiency Polymer Photovoltaic Cells, Adv. Funct. Mater. 23 (2013) 2993–3001. https://doi.org/10.1002/adfm.201202269.
[58] S. Liu, R. Liu, Y. Chen, S. Ho, J.H. Kim, F. So, Nickel oxide hole injection/transport layers for efficient solution-processed organic light-emitting diodes, Chem. Mater. 26 (2014) 4528–4534. https://doi.org/10.1021/cm501898y.
[59] K.X. Steirer, P.F. Ndione, N.E. Widjonarko, M.T. Lloyd, J. Meyer, E.L. Ratcliff, A. Kahn, N.R. Armstrong, C.J. Curtis, D.S. Ginley, J.J. Berry, D.C. Olson, Enhanced Efficiency in Plastic Solar Cells via Energy Matched Solution Processed NiOx Interlayers, Adv. Energy Mater. 1 (2011) 813–820. https://doi.org/10.1002/aenm.201100234.
[60] F. Ma, Y. Zhao, J. Li, X. Zhang, H. Gu, J. You, Nickel oxide for inverted structure perovskite solar cells, J. Energy Chem. 52 (2020) 393–411. https://doi.org/10.1016/j.jechem.2020.04.027.
[61] Y. Cheng, M. Li, X. Liu, S.H. Cheung, H.T. Chandran, H.W. Li, X. Xu, Y.M. Xie, S.K. So, H.L. Yip, S.W. Tsang, Impact of surface dipole in NiOx on the crystallization and photovoltaic performance of organometal halide perovskite solar cells, Nano Energy. 61 (2019) 496–504. https://doi.org/10.1016/j.nanoen.2019.05.004.
[62] W. Chen, F.-Z. Liu, X.-Y. Feng, A.B. Djurišić, W.K. Chan, Z.-B. He, Cesium Doped NiO x as an Efficient Hole Extraction Layer for Inverted Planar Perovskite Solar Cells, Adv. Energy Mater. 7 (2017) 1700722. https://doi.org/10.1002/aenm.201700722.
[63] Z. Liu, J. Chang, Z. Lin, L. Zhou, Z. Yang, D. Chen, C. Zhang, S. (Frank) Liu, Y. Hao, High-Performance Planar Perovskite Solar Cells Using Low Temperature, Solution–Combustion-Based Nickel Oxide Hole Transporting Layer with Efficiency Exceeding 20%, Adv. Energy Mater. 8 (2018). https://doi.org/10.1002/aenm.201703432.
[64] J. Sun, J. Lu, B. Li, L. Jiang, A.S.R. Chesman, A.D. Scully, T.R. Gengenbach, Y.-B. Cheng, J.J. Jasieniak, Inverted perovskite solar cells with high fill-factors featuring chemical bath deposited mesoporous NiO hole transporting layers, Nano Energy. 49 (2018) 163–171. https://doi.org/10.1016/J.NANOEN.2018.04.026.
[65] I.J. Park, G. Kang, M.A. Park, J.S. Kim, S.W. Seo, D.H. Kim, K. Zhu, T. Park, J.Y. Kim, Highly Efficient and Uniform 1 cm 2 Perovskite Solar Cells with an Electrochemically Deposited NiO x Hole-Extraction Layer, ChemSusChem. 10 (2017) 2660–2667. https://doi.org/10.1002/cssc.201700612.
[66] D. Di Girolamo, F. Matteocci, M. Piccinni, A. Di Carlo, D. Dini, Anodically electrodeposited NiO nanoflakes as hole selective contact in efficient air processed p-i-n perovskite solar cells, Sol. Energy Mater. Sol. Cells. 205 (2019) 110288. https://doi.org/10.1016/j.solmat.2019.110288.
[67] Y. Wu, X. Yang, W. Chen, Y. Yue, M. Cai, F. Xie, E. Bi, A. Islam, L. Han, Perovskite solar cells with 18.21% efficiency and area over 1 cm2 fabricated by heterojunction engineering, Nat. Energy. 1 (2016) 16148. https://doi.org/10.1038/nenergy.2016.148.
[68] G. Li, Y. Jiang, S. Deng, A. Tam, P. Xu, M. Wong, H.-S. Kwok, Overcoming the Limitations of Sputtered Nickel Oxide for High-Efficiency and Large-Area Perovskite Solar Cells, Adv. Sci. 4 (2017) 1700463. https://doi.org/10.1002/advs.201700463.
[69] X. Yan, J. Zheng, L. Zheng, G. Lin, H. Lin, G. Chen, B. Du, F. Zhang, Optimization of sputtering NiOx films for perovskite solar cell applications, Mater. Res. Bull. 103 (2018) 150–157. https://doi.org/10.1016/J.MATERRESBULL.2018.03.027.
[70] H. Lee, Y.T. Huang, M.W. Horn, S.P. Feng, Engineered optical and electrical performance of rf-sputtered undoped nickel oxide thin films for inverted perovskite solar cells, Sci. Rep. 8 (2018) 1–10. https://doi.org/10.1038/s41598-018-23907-0.
[71] T.J. Routledge, M. Wong-Stringer, O.S. Game, J.A. Smith, J.E. Bishop, N. Vaenas, B.G. Freestone, D.M. Coles, T. McArdle, A.R. Buckley, D.G. Lidzey, Low-temperature, high-speed reactive deposition of metal oxides for perovskite solar cells, J. Mater. Chem. A. 7 (2019) 2283–2290. https://doi.org/10.1039/C8TA10827G.
[72] J.H. Park, J. Seo, S. Park, S.S. Shin, Y.C. Kim, N.J. Jeon, H.W. Shin, T.K. Ahn, J.H. Noh, S.C. Yoon, C.S. Hwang, S. Il Seok, Efficient CH3NH3PbI3 Perovskite Solar Cells Employing Nanostructured p-Type NiO Electrode Formed by a Pulsed Laser Deposition, Adv. Mater. 27 (2015) 4013–4019. https://doi.org/10.1002/adma.201500523.
[73] Z. Qiu, H. Gong, G. Zheng, S. Yuan, H. Zhang, X. Zhu, H. Zhou, B. Cao, Enhanced physical properties of pulsed laser deposited NiO films via annealing and lithium doping for improving perovskite solar cell efficiency, J. Mater. Chem. C. 5 (2017) 7084–7094. https://doi.org/10.1039/c7tc01224a.
[74] Spin Coating: Complete Guide to Theory and Techniques | Ossila, (n.d.). https://www.ossila.com/pages/spin-coating (accessed March 4, 2021).
[75] R. Islam, G. Chen, P. Ramesh, J. Suh, N. Fuchigami, D. Lee, K.A. Littau, K. Weiner, R.T. Collins, K.C. Saraswat, Investigation of the Changes in Electronic Properties of Nickel Oxide (NiOx) Due to UV/Ozone Treatment, ACS Appl. Mater. Interfaces. 9 (2017) 17201–17207. https://doi.org/10.1021/acsami.7b01629.
[76] Z. Wang, J. Fang, Y. Mi, X. Zhu, H. Ren, X. Liu, Y. Yan, Enhanced performance of perovskite solar cells by ultraviolet-ozone treatment of mesoporous TiO 2, Appl. Surf. Sci. 436 (2018) 596–602. https://doi.org/10.1016/j.apsusc.2017.12.085.
[77] N.K. Noel, S.N. Habisreutinger, B. Wenger, M.T. Klug, M.T. Hörantner, M.B. Johnston, R.J. Nicholas, D.T. Moore, H.J. Snaith, A low viscosity, low boiling point, clean solvent system for the rapid crystallisation of highly specular perovskite films, Energy Environ. Sci. 10 (2017) 145–152. https://doi.org/10.1039/c6ee02373h.
[78] W. Zhang, M. Saliba, D.T. Moore, S.K. Pathak, M.T. Hörantner, T. Stergiopoulos, S.D. Stranks, G.E. Eperon, J.A. Alexander-Webber, A. Abate, A. Sadhanala, S. Yao, Y. Chen, R.H. Friend, L.A. Estroff, U. Wiesner, H.J. Snaith, Ultrasmooth organic-inorganic perovskite thin-film formation and crystallization for efficient planar heterojunction solar cells, Nat. Commun. 6 (2015) 1–10. https://doi.org/10.1038/ncomms7142.
[79] D.K. Unruh, T.Z. Forbes, X-ray Diffraction Techniques, in: Anal. Geomicrobiol., Cambridge University Press, 2019: pp. 215–237. https://doi.org/10.1017/9781107707399.009.
[80] W.H. Bragg, On the direct or indirect nature of the ionization by X-rays, Phil. Mag. 23 (1912) 647.
[81] H. Seyama, M. Soma, B.K.G. Theng, X-Ray Photoelectron Spectroscopy, in: Dev. Clay Sci., 2013: pp. 161–176. https://doi.org/10.1016/B978-0-08-098259-5.00007-X.
[82] Y. Jusman, S.C. Ng, N.A. Abu Osman, Investigation of CPD and HMDS sample preparation techniques for cervical cells in developing computer-aided screening system based on FE-SEM/EDX, Sci. World J. 2014 (2014). https://doi.org/10.1155/2014/289817.
[83] Improved Surface Characterization with AFM Imaging - Tech Briefs, (n.d.). https://www.techbriefs.com/component/content/article/tb/supplements/pit/features/applications/27833 (accessed March 6, 2021).
[84] File:Schematic of UV- visible spectrophotometer.png - Wikimedia Commons, (n.d.). https://commons.wikimedia.org/wiki/File:Schematic_of_UV-_visible_spectrophotometer.png (accessed March 6, 2021).
[85] J.D. Ingle, S.R. Crouch, Spectrochemical Analysis, Prentice Hall, 1988. https://books.google.com.tw/books?id=1NHvAAAAMAAJ.
[86] J. Tauc, Optical properties and electronic structure of amorphous Ge and Si, Mater. Res. Bull. 3 (1968) 37–46. https://doi.org/10.1016/0025-5408(68)90023-8.
[87] F.A. Lindholm, J.G. Fossum, E.L. Burgess, Application of the Superposition Principle to Solar-Cell Analysis, IEEE Trans. Electron Devices. 26 (1979) 165–171. https://doi.org/10.1109/T-ED.1979.19400.
[88] G.A. Sepalage, S. Meyer, A. Pascoe, A.D. Scully, F. Huang, U. Bach, Y.-B. Cheng, L. Spiccia, Copper(I) Iodide as Hole-Conductor in Planar Perovskite Solar Cells: Probing the Origin of J - V Hysteresis, Adv. Funct. Mater. 25 (2015) 5650–5661. https://doi.org/10.1002/adfm.201502541.
[89] G. Katumba, J. Lu, L. Olumekor, G. Westin, E. Wäckelgård, Low cost selective solar absorber coatings: Characteristics of carbon-in-silica synthesized with sol-gel technique, J. Sol-Gel Sci. Technol. 36 (2005) 33–43. https://doi.org/10.1007/s10971-005-4793-4.
[90] A.A. Al-Ghamdi, W.E. Mahmoud, S.J. Yaghmour, F.M. Al-Marzouki, Structure and optical properties of nanocrystalline NiO thin film synthesized by sol-gel spin-coating method, J. Alloys Compd. 486 (2009) 9–13. https://doi.org/10.1016/j.jallcom.2009.06.139.
[91] G.E. Eperon, D. Moerman, D.S. Ginger, Anticorrelation between Local Photoluminescence and Photocurrent Suggests Variability in Contact to Active Layer in Perovskite Solar Cells, ACS Nano. 10 (2016) 10258–10266. https://doi.org/10.1021/acsnano.6b05825.
[92] S. Bai, P. Da, C. Li, Z. Wang, Z. Yuan, F. Fu, M. Kawecki, X. Liu, N. Sakai, J.T.-W. Wang, S. Huettner, S. Buecheler, M. Fahlman, F. Gao, H.J. Snaith, Planar perovskite solar cells with long-term stability using ionic liquid additives, Nature. 571 (2019) 245–250. https://doi.org/10.1038/s41586-019-1357-2.
[93] Y.R. Lin, Y.S. Liao, H.T. Hsiao, C.P. Chen, Two-step annealing of NiOx enhances the NiOx–perovskite interface for high-performance ambient-stable p–i–n perovskite solar cells, Appl. Surf. Sci. 504 (2020) 144478. https://doi.org/10.1016/j.apsusc.2019.144478.
[94] S. Nandy, B. Saha, M.K. Mitra, K.K. Chattopadhyay, Effect of oxygen partial pressure on the electrical and optical properties of highly (200) oriented p-type Ni1-x O films by DC sputtering, J. Mater. Sci. 42 (2007) 5766–5772. https://doi.org/10.1007/s10853-006-1153-x.
[95] S.S. Mali, H. Kim, H.H. Kim, S.E. Shim, C.K. Hong, Nanoporous p-type NiOx electrode for p-i-n inverted perovskite solar cell toward air stability, Mater. Today. 21 (2018) 483–500. https://doi.org/10.1016/J.MATTOD.2017.12.002.
[96] Y. Wu, X. Yang, W. Chen, Y. Yue, M. Cai, F. Xie, E. Bi, A. Islam, L. Han, Perovskite solar cells with 18.21% efficiency and area over 1 cm2 fabricated by heterojunction engineering, Nat. Energy. 1 (2016) 1–7. https://doi.org/10.1038/nenergy.2016.148.
[97] D. Liu, Y. Li, J. Yuan, Q. Hong, G. Shi, D. Yuan, J. Wei, C. Huang, J. Tang, M.K. Fung, Improved performance of inverted planar perovskite solar cells with F4-TCNQ doped PEDOT:PSS hole transport layers, J. Mater. Chem. A. 5 (2017) 5701–5708. https://doi.org/10.1039/C6TA10212C.
[98] C.H. Tsai, C.M. Lin, C.H. Kuei, Improving the performance of perovskite solar cells by adding 1,8-diiodooctane in the CH3NH3PbI3 perovskite layer, Sol. Energy. 176 (2018) 178–185. https://doi.org/10.1016/j.solener.2018.10.037.
[99] M. Imran, H. Coskun, N.A. Khan, J. Ouyang, Role of annealing temperature of nickel oxide (NiOx) as hole transport layer in work function alignment with perovskite, Appl. Phys. A. 127 (2021) 117. https://doi.org/10.1007/s00339-021-04283-5.
[100] J.W. Jung, C.C. Chueh, A.K.Y. Jen, A Low-Temperature, Solution-Processable, Cu-Doped Nickel Oxide Hole-Transporting Layer via the Combustion Method for High-Performance Thin-Film Perovskite Solar Cells, Adv. Mater. 27 (2015) 7874–7880. https://doi.org/10.1002/adma.201503298.
[101] A.G. Merzhanov, The chemistry of self-propagating high-temperature synthesis, J. Mater. Chem. 14 (2004) 1779–1786. https://doi.org/10.1039/b401358c.
[102] K. Deshpande, A. Mukasyan, A. Varma, Direct synthesis of iron oxide nanopowders by the combustion approach: Reaction mechanism and properties, Chem. Mater. 16 (2004) 4896–4904. https://doi.org/10.1021/cm040061m.
[103] M. Epifani, E. Melissano, G. Pace, M. Schioppa, Precursors for the combustion synthesis of metal oxides from the sol-gel processing of metal complexes, J. Eur. Ceram. Soc. 27 (2007) 115–123. https://doi.org/10.1016/j.jeurceramsoc.2006.04.084.
[104] S. Bai, M. Cao, Y. Jin, X. Dai, X. Liang, Z. Ye, M. Li, J. Cheng, X. Xiao, Z. Wu, Z. Xia, B. Sun, E. Wang, Y. Mo, F. Gao, F. Zhang, Low-temperature combustion-synthesized nickel oxide thin films as hole-transport interlayers for solution-processed optoelectronic devices, Adv. Energy Mater. 4 (2014) 1301460. https://doi.org/10.1002/aenm.201301460.
[105] Y. Liu, H. Cai, J. Su, X. Ye, J. Yang, X. Liang, J. Guan, X. Zhou, J. Yin, J. Ni, J. Li, J. Zhang, Solution-combustion-based nickel oxide hole transport layers via fuel regulation in inverted planar perovskite solar cells, J. Mater. Sci. Mater. Electron. 31 (2020) 15225–15232. https://doi.org/10.1007/s10854-020-04087-y.
[106] S. Dewan, M. Tomar, R.P. Tandon, V. Gupta, Zn doping induced conductivity transformation in NiO films for realization of p-n homo junction diode, J. Appl. Phys. 121 (2017) 215307. https://doi.org/10.1063/1.4984580.
[107] Z. Hu, D. Chen, P. Yang, L. Yang, L. Qin, Y. Huang, X. Zhao, Sol-gel-processed yttrium-doped NiO as hole transport layer in inverted perovskite solar cells for enhanced performance, Appl. Surf. Sci. 441 (2018) 258–264. https://doi.org/10.1016/J.APSUSC.2018.01.236.
[108] X. Wan, Y. Jiang, Z. Qiu, H. Zhang, X. Zhu, I. Sikandar, X. Liu, X. Chen, B. Cao, Zinc as a New Dopant for NiOx-Based Planar Perovskite Solar Cells with Stable Efficiency near 20%, ACS Appl. Energy Mater. 1 (2018) 3947–3954. https://doi.org/10.1021/acsaem.8b00671.
[109] M.A. Mahmud, N.K. Elumalai, M.B. Upama, D. Wang, K.H. Chan, M. Wright, C. Xu, F. Haque, A. Uddin, Low temperature processed ZnO thin film as electron transport layer for efficient perovskite solar cells, Sol. Energy Mater. Sol. Cells. 159 (2017) 251–264. https://doi.org/10.1016/j.solmat.2016.09.014.
[110] J.H. Lee, Y.W. Noh, I.S. Jin, J.W. Jung, Efficient planar heterojunction perovskite solar cells employing a solution-processed Zn-doped NiOX hole transport layer, Electrochim. Acta. 284 (2018) 253–259. https://doi.org/10.1016/j.electacta.2018.07.178.
[111] S.S. Shin, S.J. Lee, S. Il Seok, Metal Oxide Charge Transport Layers for Efficient and Stable Perovskite Solar Cells, Adv. Funct. Mater. 29 (2019). https://doi.org/10.1002/adfm.201900455.
[112] W. Nie, H. Tsai, J.C. Blancon, F. Liu, C.C. Stoumpos, B. Traore, M. Kepenekian, O. Durand, C. Katan, S. Tretiak, J. Crochet, P.M. Ajayan, M. Kanatzidis, J. Even, A.D. Mohite, Critical Role of Interface and Crystallinity on the Performance and Photostability of Perovskite Solar Cell on Nickel Oxide, Adv. Mater. 30 (2018). https://doi.org/10.1002/adma.201703879.
[113] W. Chen, Y. Wu, J. Fan, A.B. Djurišić, F. Liu, H.W. Tam, A. Ng, C. Surya, W.K. Chan, D. Wang, Z.-B. He, Understanding the Doping Effect on NiO: Toward High-Performance Inverted Perovskite Solar Cells, Adv. Energy Mater. 8 (2018) 1703519. https://doi.org/10.1002/aenm.201703519.
[114] Q. He, K. Yao, X. Wang, X. Xia, S. Leng, F. Li, Room-Temperature and Solution-Processable Cu-Doped Nickel Oxide Nanoparticles for Efficient Hole-Transport Layers of Flexible Large-Area Perovskite Solar Cells, ACS Appl. Mater. Interfaces. 9 (2017) 41887–41897. https://doi.org/10.1021/acsami.7b13621.
[115] A. Huang, L. Lei, Y. Chen, Y. Yu, Y. Zhou, Y. Liu, S. Yang, S. Bao, R. Li, P. Jin, Minimizing the energy loss of perovskite solar cells with Cu+ doped NiOx processed at room temperature, Sol. Energy Mater. Sol. Cells. 182 (2018) 128–135. https://doi.org/10.1016/J.SOLMAT.2018.01.025.
[116] P.H. Lee, B.T. Li, C.F. Lee, Z.H. Huang, Y.C. Huang, W.F. Su, High-efficiency perovskite solar cell using cobalt doped nickel oxide hole transport layer fabricated by NIR process, Sol. Energy Mater. Sol. Cells. 208 (2020) 110352. https://doi.org/10.1016/j.solmat.2019.110352.
[117] P.S. Chandrasekhar, Y.H. Seo, Y.J. Noh, S.I. Na, Room temperature solution-processed Fe doped NiOx as a novel hole transport layer for high efficient perovskite solar cells, Appl. Surf. Sci. 481 (2019) 588–596. https://doi.org/10.1016/j.apsusc.2019.03.164.
[118] W. Chen, Y. Wu, B. Tu, F. Liu, A.B. Djurišić, Z. He, Inverted planar organic-inorganic hybrid perovskite solar cells with NiOx hole-transport layers as light-in window, Appl. Surf. Sci. 451 (2018) 325–332. https://doi.org/10.1016/J.APSUSC.2018.04.230.
[119] F. Jiang, W.C.H. Choy, X. Li, D. Zhang, J. Cheng, Post-treatment-Free Solution-Processed Non-stoichiometric NiO x Nanoparticles for Efficient Hole-Transport Layers of Organic Optoelectronic Devices, Adv. Mater. 27 (2015) 2930–2937. https://doi.org/10.1002/adma.201405391.
[120] A. Liu, H. Zhu, Z. Guo, Y. Meng, G. Liu, E. Fortunato, R. Martins, F. Shan, Solution Combustion Synthesis: Low-Temperature Processing for p-Type Cu:NiO Thin Films for Transparent Electronics, Adv. Mater. 29 (2017) 1701599. https://doi.org/10.1002/adma.201701599.
[121] D. Wang, R. Xu, X. Wang, Y. Li, NiO nanorings and their unexpected catalytic property for CO oxidation, Nanotechnology. 17 (2006) 979–983. https://doi.org/10.1088/0957-4484/17/4/023.
[122] Y. Cudennec, A. Lecerf, The transformation of Cu(OH)2 into CuO, revisited, Solid State Sci. 5 (2003) 1471–1474. https://doi.org/10.1016/j.solidstatesciences.2003.09.009.
[123] S. Seo, I.J. Park, M. Kim, S. Lee, C. Bae, H.S. Jung, N.G. Park, J.Y. Kim, H. Shin, An ultra-thin, un-doped NiO hole transporting layer of highly efficient (16.4%) organic-inorganic hybrid perovskite solar cells, Nanoscale. 8 (2016) 11403–11412. https://doi.org/10.1039/c6nr01601d.
[124] J. Cui, F. Meng, H. Zhang, K. Cao, H. Yuan, Y. Cheng, F. Huang, M. Wang, CH3NH3PbI3-based planar solar cells with magnetron-sputtered nickel oxide, ACS Appl. Mater. Interfaces. 6 (2014) 22862–22870. https://doi.org/10.1021/am507108u.
[125] J. Byun, H. Cho, C. Wolf, M. Jang, A. Sadhanala, R.H. Friend, H. Yang, T.W. Lee, Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes, Adv. Mater. 28 (2016) 7515–7520. https://doi.org/10.1002/adma.201601369.
[126] V. Gonzalez-Pedro, E.J. Juarez-Perez, W.S. Arsyad, E.M. Barea, F. Fabregat-Santiago, I. Mora-Sero, J. Bisquert, General working principles of CH3NH3PbX3 perovskite solar cells, Nano Lett. 14 (2014) 888–893. https://doi.org/10.1021/nl404252e.
[127] C. Eames, J.M. Frost, P.R.F. Barnes, B.C. O’Regan, A. Walsh, M.S. Islam, Ionic transport in hybrid lead iodide perovskite solar cells, Nat. Commun. 6 (2015) 1–8. https://doi.org/10.1038/ncomms8497.
[128] G.A. Sepalage, S. Meyer, A. Pascoe, A.D. Scully, F. Huang, U. Bach, Y.B. Cheng, L. Spiccia, Copper(I) Iodide as Hole-Conductor in Planar Perovskite Solar Cells: Probing the Origin of J-V Hysteresis, Adv. Funct. Mater. 25 (2015) 5650–5661. https://doi.org/10.1002/adfm.201502541.