臺灣博碩士論文加值系統

二維氧化物是二維材料中的一大類別，而二維氧化物又可以區分成兩個小類：二維金屬氧化物及二維鈣鈦礦氧化物。二維氧化物有相當多元的結構及電性，因其具有量子侷限效應及表面效應，二維氧化物相較於其塊材，具有許多特殊的物理及化學性質，二維氧化物常用於電容、二次電池及催化劑領域中。
Ca2Nb3O10 (CNO)是鈣鈦礦結構的二維氧化物，他是一種N型寬能隙的半導體，其導帶底部位置與常用於太陽能電池吸光層的有機-無機鈣鈦礦接近，因此CNO相當適合作為有機-無機鈣鈦礦太陽能電池的電子傳輸層，用來接收吸光層產生的電子，且不讓電洞進入。此外，相較於一般需要高溫(> 500 ˚C)燒結的二氧化鈦電子傳輸層，CNO的鍍膜僅須相對低溫(< 150 ˚C)的溶劑製程。
本論文中，使用低溫的Langmuir-Blodgett沉積法來製作CNO電子傳輸層，並製做成有機-無機鈣鈦礦太陽能電池，最好的元件效率為14.10%，與一般高溫二氧化鈦電子傳輸層製成的元件效率相當(14.07%)，另外，CNO電子傳輸層擁有更好的電子傳輸能力。論文中證明了CNO是非常有潛力的電子傳輸層，可用來製做全鈣鈦礦結構的太陽能電池。

Two-dimensional (2D) oxides are a large group of 2D materials. These 2D oxides can be divided into two subgroups: 2D metal oxides and 2D perovskite oxides. They are rich in structural diversity, electronic properties, and have novel physical and chemical properties from quantum confinement or surface effects comparing to their bulk states. 2D oxides are widely applied in the nanocapacitors, secondary batteries, and photocatalysts fields.
Among the 2D perovskite oxides, Ca2Nb3O10 (CNO) atomic sheet is an n-type wide bandgap semiconductor. It has well aligned conduction band minimum with that of the lead halide perovskite, which is an efficient light absorber for solar cell application. These properties make CNO a promising electron transport material to extract electrons and block holes from lead halide perovskite light absorber. On the other hand, comparing to the conventional high temperature (> 500 ˚C) sintered compact-TiO2 electron transport layer, CNO can be deposited with relative low temperature (< 150 ˚C) solution process.
In this work, we deposited CNO with low temperature Langmuir-Blodgett deposition method as electron transport layer to fabricate perovskite solar cell. The resultant devices showed best efficiency of 14.10%, which is compatible to the conventional high-temperature sintered compact-TiO2 device (14.07%). Moreover, the CNO based devices showed better electron transport ability than the conventional ones. Our work showed that CNO atomic sheet is a highly promising electron transport material for low-temperature solution processed all perovskite structure solar cells.

口試委員會審定書 #
TABLE OF CONTENT i
誌謝 ii
中文摘要 iv
ABSTRACT v
CONTENTS vi
LIST OF FIGURES ix
LIST OF TABLES xvi
Chapter 1 Introduction 1
1.1 Two-dimensional oxide nanosheets 1
1.1.1 Introduction of oxide nanosheets 1
1.1.2 Structure of oxide nanosheets 2
1.1.3 Properties of oxide nanosheets 4
1.2 Solar cells and perovskite solar cells 7
1.2.1 Sun, energy and solar cells 7
1.2.2 Structure and properties of perovskite 9
1.2.3 History of perovskite solar cells 12
1.3 Motivation 15
Chapter 2 Literature Review 16
2.1 Two dimensional oxide materials 16
2.1.1 Synthesis and deposition of oxide nanosheets 16
2.1.2 Application of oxide nanosheets 20
2.2 Perovskite solar cells 25
2.2.1 Deposition of perovskite thin film 25
2.2.2 Device architectures of perovskite solar cells 28
2.2.3 Transport layers in perovskite solar cells 30
2.3 Two-dimensional materials for perovskite solar cells 36
2.3.1 Two-dimensional materials as electrodes 36
2.3.2 Two-dimensional materials as electron transport layers 38
2.3.3 Two-dimensional materials as hole transport layers 40
Chapter 3 Experimental section 42
3.1 Fabrication of perovskite solar cells 42
3.1.1 Synthesis of Ca2Nb3O10 atomic sheet 42
3.1.2 Deposition of Ca2Nb3O10 atomic sheet 43
3.1.3 Device fabrication 44
3.2 Working mechanism of perovskite solar cells 46
3.3 Photovoltaic characteristic 48
3.3.1 Solar spectrum 48
3.3.2 I-V characteristic of the photovoltaic devices 49
3.3.3 Incident photo-to-current efficiency 52
3.4 Characteristic and measurement 54
3.4.1 Transmission electron microscope 54
3.4.2 Scanning electron microscope 55
3.4.3 Atomic force microscopy 56
3.4.4 Photoluminescence and time-resolved photoluminescence 57
Chapter 4 Two-dimensional perovskite oxide atomic sheets as electron transport layer 59
4.1 Introduction 59
4.2 Surface coverage of different layers of Ca2Nb3O10 atomic sheet 62
4.3 Performances of perovskite solar cells with Ca2Nb3O10 atomic sheets 66
4.4 Electron transport properties in Ca2Nb3O10 atomic sheet 71
4.5 Conclusion 76
Chapter 5 Future prospect 77
REFERENCE 79

1Novoselov, K. S. et al. Electric field effect in atomically thin carbon films. science 306, 666-669 (2004).
2Geim, A. K. Graphene: status and prospects. science 324, 1530-1534 (2009).
3Sasaki, T. & Watanabe, M. Osmotic swelling to exfoliation. Exceptionally high degrees of hydration of a layered titanate. J. Am. Chem. Soc. 120, 4682-4689 (1998).
4Sasaki, T., Watanabe, M., Hashizume, H., Yamada, H. & Nakazawa, H. Macromolecule-like aspects for a colloidal suspension of an exfoliated titanate. Pairwise association of nanosheets and dynamic reassembling process initiated from it. J. Am. Chem. Soc. 118, 8329-8335 (1996).
5Osada, M. & Sasaki, T. Exfoliated oxide nanosheets: new solution to nanoelectronics. Journal of Materials Chemistry 19, 2503, doi:10.1039/b820160a (2009).
6Tusche, C., Meyerheim, H. & Kirschner, J. Observation of depolarized ZnO (0001) monolayers: formation of unreconstructed planar sheets. Phys. Rev. Lett. 99, 026102 (2007).
7Atrei, A., Ferrari, A. M., Szieberth, D., Cortigiani, B. & Rovida, G. Lepidocrocite-like structure of the TiO 2 monolayer grown on Ag (100). PCCP 12, 11587-11595 (2010).
8Kalantar-zadeh, K. et al. Two dimensional and layered transition metal oxides. Applied Materials Today 5, 73-89, doi:10.1016/j.apmt.2016.09.012 (2016).
9Osada, M. & Sasaki, T. Two-Dimensional Dielectric Nanosheets: Novel Nanoelectronics From Nanocrystal Building Blocks. Adv. Mater. 24, 210-228, doi:10.1002/adma.201103241 (2012).
10Osada, M. et al. High‐κ Dielectric Nanofilms Fabricated from Titania Nanosheets. Adv. Mater. 18, 1023-1027 (2006).
11Osada, M. et al. Langmuir–Blodgett Fabrication of Nanosheet-Based Dielectric Films without an Interfacial Dead Layer. Japanese Journal of Applied Physics 47, 7556 (2008).
12Fang, M., Kim, C. H. & Mallouk, T. E. Dielectric properties of the lamellar niobates and titanoniobates AM2Nb3O10 and ATiNbO5 (A= H, K, M= Ca, Pb), and their condensation products Ca4Nb6O19 and Ti2Nb2O9. Chem. Mater. 11, 1519-1525 (1999).
13Li, B.-W. et al. Impact of perovskite layer stacking on dielectric responses in KCa 2 Na n− 3 Nb n O 3 n+ 1 (n= 3–6) Dion–Jacobson homologous series. Appl. Phys. Lett. 96, 182903 (2010).
14Wang, L., Ding, L.-Y., Zhang, S.-T., Chen, Y.-F. & Liu, Z.-G. Structure and electrical properties of c-axis epitaxial Srm− 3Bi4TimO3m+ 3 (m= 5 and 6) thin films. Solid State Commun. 149, 2061-2064 (2009).
15Matsumoto, Y. et al. Room-temperature ferromagnetism in transparent transition metal-doped titanium dioxide. Science 291, 854-856 (2001).
16Osada, M., Ebina, Y., Takada, K. & Sasaki, T. Gigantic Magneto–Optical Effects in Multilayer Assemblies of Two‐Dimensional Titania Nanosheets. Adv. Mater. 18, 295-299 (2006).
17Liu, Z. et al. Synthesis, anion exchange, and delamination of Co− Al layered double hydroxide: assembly of the exfoliated nanosheet/polyanion composite films and magneto-optical studies. J. Am. Chem. Soc. 128, 4872-4880 (2006).
18Oh, S. M., Patil, S. B., Jin, X. Y. & Hwang, S. J. Recent Applications of 2D Inorganic Nanosheets for Emerging Energy Storage System. Chemistry-a European Journal 24, 4757-+, doi:10.1002/chem.201704284 (2018).
19Osada, M. & Sasaki, T. Exfoliated oxide nanosheets: new solution to nanoelectronics. Journal of Materials Chemistry 19, 2503-2511, doi:10.1039/b820160a (2009).
20UNDP, U. WEC (2000) World Energy Assessment: Energy and the Challenge of Sustainability. United Nations Development Programme, New York (2000).
21Grätzel, M. Photoelectrochemical cells. nature 414, 338 (2001).
22Green, M. A. Third generation photovoltaics: solar cells for 2020 and beyond. Physica E: Low-dimensional Systems and Nanostructures 14, 65-70 (2002).
23Chapin, D. M., Fuller, C. & Pearson, G. A new silicon p‐n junction photocell for converting solar radiation into electrical power. J. Appl. Phys. 25, 676-677 (1954).
24Jayawardena, K. I. et al. ‘Inorganics-in-Organics’: recent developments and outlook for 4G polymer solar cells. Nanoscale 5, 8411-8427 (2013).
25Best Research-Cell Efficiencies, <https://www.nrel.gov/pv/assets/images/efficiency-chart.png> (2017).
26Cheng, Z. & Lin, J. Layered organic–inorganic hybrid perovskites: structure, optical properties, film preparation, patterning and templating engineering. CrystEngComm 12, 2646-2662 (2010).
27Marinova, N., Valero, S. & Delgado, J. L. Organic and perovskite solar cells: Working principles, materials and interfaces. J. Colloid Interface Sci. 488, 373-389, doi:10.1016/j.jcis.2016.11.021 (2017).
28Xu, X., Randorn, C., Efstathiou, P. & Irvine, J. T. A red metallic oxide photocatalyst. Nat. Mater. 11, 595 (2012).
29Kagan, C., Mitzi, D. & Dimitrakopoulos, C. Organic-inorganic hybrid materials as semiconducting channels in thin-film field-effect transistors. Science 286, 945-947 (1999).
30Kieslich, G., Sun, S. & Cheetham, A. K. Solid-state principles applied to organic–inorganic perovskites: new tricks for an old dog. Chemical Science 5, 4712-4715 (2014).
31Zhao, Y. X. & Zhu, K. Organic-inorganic hybrid lead halide perovskites for optoelectronic and electronic applications. Chem. Soc. Rev. 45, 655-689, doi:10.1039/c4cs00458b (2016).
32Mitzi, D. B. Templating and structural engineering in organic–inorganic perovskites. J. Chem. Soc., Dalton Trans., 1-12 (2001).
33Noh, J. H., Im, S. H., Heo, J. H., Mandal, T. N. & Seok, S. I. Chemical management for colorful, efficient, and stable inorganic–organic hybrid nanostructured solar cells. Nano Lett. 13, 1764-1769 (2013).
34Yin, W.-J., Yan, Y. & Wei, S.-H. Anomalous alloy properties in mixed halide perovskites. The journal of physical chemistry letters 5, 3625-3631 (2014).
35Mosconi, E., Azpiroz, J. M. & De Angelis, F. Ab initio molecular dynamics simulations of methylammonium lead iodide perovskite degradation by water. Chem. Mater. 27, 4885-4892 (2015).
36Papavassiliou, G. C. Synthetic three-and lower-dimensional semiconductors based on inorganic units. Molecular Crystals and Liquid Crystals 286, 231-238 (1996).
37Giorgi, G., Fujisawa, J.-I., Segawa, H. & Yamashita, K. Small photocarrier effective masses featuring ambipolar transport in methylammonium lead iodide perovskite: a density functional analysis. The journal of physical chemistry letters 4, 4213-4216 (2013).
38Xing, G. et al. Long-range balanced electron-and hole-transport lengths in organic-inorganic CH3NH3PbI3. Science 342, 344-347 (2013).
39D''Innocenzo, V. et al. Excitons versus free charges in organo-lead tri-halide perovskites. Nat Commun 5, 3586, doi:10.1038/ncomms4586 (2014).
40Kojima, A., Teshima, K., Shirai, Y. & Miyasaka, T. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. J. Am. Chem. Soc. 131, 6050-6051 (2009).
41Im, J.-H., Lee, C.-R., Lee, J.-W., Park, S.-W. & Park, N.-G. 6.5% efficient perovskite quantum-dot-sensitized solar cell. Nanoscale 3, 4088-4093 (2011).
42Kim, H.-S. et al. Lead iodide perovskite sensitized all-solid-state submicron thin film mesoscopic solar cell with efficiency exceeding 9%. Scientific reports 2, 591 (2012).
43Zhou, H. et al. Interface engineering of highly efficient perovskite solar cells. Science 345, 542-546 (2014).
44Jeon, N. J. et al. Compositional engineering of perovskite materials for high-performance solar cells. Nature 517, 476-480, doi:10.1038/nature14133 (2015).
45Yang, W. S. et al. Iodide management in formamidinium-lead-halide–based perovskite layers for efficient solar cells. Science 356, 1376-1379 (2017).
46Ono, L. K. & Qi, Y. B. Research progress on organic-inorganic halide perovskite materials and solar cells. Journal of Physics D-Applied Physics 51, doi:10.1088/1361-6463/aaa727 (2018).
47Chen, T. P. et al. Self-Assembly Atomic Stacking Transport Layer of 2D Layered Titania for Perovskite Solar Cells with Extended UV Stability. Advanced Energy Materials 8, doi:10.1002/aenm.201701722 (2018).
48Liu, K.-K. et al. Growth of large-area and highly crystalline MoS2 thin layers on insulating substrates. Nano Lett. 12, 1538-1544 (2012).
49Liu, Y. et al. Ultrathin HNbWO 6 nanosheets: facile synthesis and enhanced hydrogen evolution performance from photocatalytic water splitting. Chem. Commun. 51, 15125-15128 (2015).
50Zhao, C., Zhang, H., Si, W. & Wu, H. Mass production of two-dimensional oxides by rapid heating of hydrous chlorides. Nat. Commun. 7, 12543 (2016).
51Nicolosi, V., Chhowalla, M., Kanatzidis, M. G., Strano, M. S. & Coleman, J. N. Liquid exfoliation of layered materials. Science 340, 1226419 (2013).
52Omomo, Y., Sasaki, T., Wang, L. & Watanabe, M. Redoxable nanosheet crystallites of MnO2 derived via delamination of a layered manganese oxide. J. Am. Chem. Soc. 125, 3568-3575 (2003).
53Fukuda, K., Nakai, I., Ebina, Y., Ma, R. & Sasaki, T. Colloidal unilamellar layers of tantalum oxide with open channels. Inorg. Chem. 46, 4787-4789 (2007).
54Fukuda, K. et al. Synthesis of nanosheet crystallites of ruthenate with an α-NaFeO2-related structure and its electrochemical supercapacitor property. Inorg. Chem. 49, 4391-4393 (2010).
55Osada, M. & Sasaki, T. Nanosheet architectonics: a hierarchically structured assembly for tailored fusion materials. Polym. J. 47, 89-98, doi:10.1038/pj.2014.111 (2015).
56Kim, H. J., Osada, M. & Sasaki, T. Advanced capacitor technology based on two-dimensional nanosheets. Japanese Journal of Applied Physics 55, doi:10.7567/jjap.55.1102a3 (2016).
57Wang, C. et al. All-nanosheet ultrathin capacitors assembled layer-by-layer via solution-based processes. ACS nano 8, 2658-2666 (2014).
58Li, B.-W. et al. High thermal robustness of molecularly thin perovskite nanosheets and implications for superior dielectric properties. ACS nano 8, 5449-5461 (2014).
59Kim, Y.-H. et al. 2D perovskite nanosheets with thermally-stable high-κ response: A new platform for high-temperature capacitors. ACS Appl. Mater. Interfaces 6, 19510-19514 (2014).
60Duan, X. et al. 3D hierarchical CuO mesocrystals from ionic liquid precursors: towards better electrochemical performance for Li-ion batteries. Journal of Materials Chemistry A 4, 8402-8411 (2016).
61Zhang, F., Zhu, J., Zhang, D., Schwingenschlögl, U. & Alshareef, H. N. Two-dimensional SnO anodes with a tunable number of atomic layers for sodium ion batteries. Nano Lett. 17, 1302-1311 (2017).
62Kang, J.-H., Paek, S.-M., Hwang, S.-J. & Choy, J.-H. Pre-swelled nanostructured electrode for lithium ion battery: TiO 2-pillared layered MnO 2. Journal of Materials Chemistry 20, 2033-2038 (2010).
63Liang, X. et al. A highly efficient polysulfide mediator for lithium–sulfur batteries. Nat. Commun. 6, 5682 (2015).
64Li, Z., Zhang, J. & Lou, X. W. D. Hollow carbon nanofibers filled with MnO2 nanosheets as efficient sulfur hosts for lithium–sulfur batteries. Angew. Chem. Int. Ed. 54, 12886-12890 (2015).
65Fan, Q., Liu, W., Weng, Z., Sun, Y. & Wang, H. Ternary hybrid material for high-performance lithium–sulfur battery. J. Am. Chem. Soc. 137, 12946-12953 (2015).
66Yuan, C., Zhu, S., Cao, H., Hou, L. & Lin, J. Hierarchical sulfur-impregnated hydrogenated TiO2 mesoporous spheres comprising anatase nanosheets with highly exposed (001) facets for advanced Li-S batteries. Nanotechnology 27, 045403 (2015).
67Zhuang, L. et al. Ultrathin Iron‐Cobalt Oxide Nanosheets with Abundant Oxygen Vacancies for the Oxygen Evolution Reaction. Adv. Mater. 29 (2017).
68Jin, X., Lim, J., Lee, N.-S. & Hwang, S.-J. A powerful role of exfoliated metal oxide 2D nanosheets as additives for improving electrocatalyst functionality of graphene. Electrochim. Acta 235, 720-729 (2017).
69Maeda, K. & Mallouk, T. E. Comparison of two- and three-layer restacked Dion–Jacobson phase niobate nanosheets as catalysts for photochemical hydrogen evolution. Journal of Materials Chemistry 19, 4813, doi:10.1039/b903692j (2009).
70Mottram, A. D. et al. Quasi two-dimensional dye-sensitized In2O3 phototransistors for ultrahigh responsivity and photosensitivity photodetector applications. ACS Appl. Mater. Interfaces 8, 4894-4902 (2016).
71Sun, Z. et al. Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets. Nat. Commun. 5, 3813 (2014).
72Leijtens, T. et al. Overcoming ultraviolet light instability of sensitized TiO2 with meso-superstructured organometal tri-halide perovskite solar cells. Nat. Commun. 4, 2885 (2013).
73Liu, M., Johnston, M. B. & Snaith, H. J. Efficient planar heterojunction perovskite solar cells by vapour deposition. Nature 501, 395 (2013).
74Eperon, G. E., Burlakov, V. M., Docampo, P., Goriely, A. & Snaith, H. J. Morphological control for high performance, solution‐processed planar heterojunction perovskite solar cells. Adv. Funct. Mater. 24, 151-157 (2014).
75Yu, H. et al. The Role of Chlorine in the Formation Process of “CH3NH3PbI3‐xClx” Perovskite. Adv. Funct. Mater. 24, 7102-7108 (2014).
76Jeon, N. J. et al. Solvent engineering for high-performance inorganic-organic hybrid perovskite solar cells. Nat Mater 13, 897-903, doi:10.1038/nmat4014 (2014).
77Xiao, M. et al. A fast deposition‐crystallization procedure for highly efficient lead iodide perovskite thin‐film solar cells. Angew. Chem. 126, 10056-10061 (2014).
78Preda, N. et al. Films and crystalline powder of PbI 2 intercalated with ammonia and pyridine. Journal of Materials Science: Materials in Electronics 20, 465-470 (2009).
79Burschka, J. et al. Sequential deposition as a route to high-performance perovskite-sensitized solar cells. Nature 499, 316 (2013).
80Zhao, Y., Nardes, A. M. & Zhu, K. Solid-state mesostructured perovskite CH3NH3PbI3 solar cells: charge transport, recombination, and diffusion length. The journal of physical chemistry letters 5, 490-494 (2014).
81Leijtens, T. et al. Overcoming ultraviolet light instability of sensitized TiO 2 with meso-superstructured organometal tri-halide perovskite solar cells. Nat. Commun. 4, 2885 (2013).
82Heo, J. H. et al. Efficient inorganic–organic hybrid heterojunction solar cells containing perovskite compound and polymeric hole conductors. Nature photonics 7, 486 (2013).
83You, J. et al. Low-temperature solution-processed perovskite solar cells with high efficiency and flexibility. (2014).
84Calio, L., Kazim, S., Gratzel, M. & Ahmad, S. Hole-Transport Materials for Perovskite Solar Cells. Angewandte Chemie-International Edition 55, 14522-14545, doi:10.1002/anie.201601757 (2016).
85Domanski, K. et al. Not all that glitters is gold: Metal-migration-induced degradation in perovskite solar cells. ACS nano 10, 6306-6314 (2016).
86Christians, J. A., Fung, R. C. & Kamat, P. V. An inorganic hole conductor for organo-lead halide perovskite solar cells. Improved hole conductivity with copper iodide. J. Am. Chem. Soc. 136, 758-764 (2013).
87Ito, S. et al. Carbon‐double‐bond‐free printed solar cells from TiO2/CH3NH3PbI3/CuSCN/Au: structural control and photoaging effects. ChemPhysChem 15, 1194-1200 (2014).
88Ye, S. et al. CuSCN-based inverted planar perovskite solar cell with an average PCE of 15.6%. Nano Lett. 15, 3723-3728 (2015).
89Zuo, C. & Ding, L. Solution‐Processed Cu2O and CuO as Hole Transport Materials for Efficient Perovskite Solar Cells. Small 11, 5528-5532 (2015).
90Subbiah, A. S. et al. Inorganic hole conducting layers for perovskite-based solar cells. The journal of physical chemistry letters 5, 1748-1753 (2014).
91Zhu, Z. et al. High‐performance hole‐extraction layer of sol–gel‐processed NiO nanocrystals for inverted planar perovskite solar cells. Angew. Chem. 126, 12779-12783 (2014).
92Wang, H.-Q., Li, N., Guldal, N. S. & Brabec, C. J. Nanocrystal V2O5 thin film as hole-extraction layer in normal architecture organic solar cells. Org. Electron. 13, 3014-3021 (2012).
93Saliba, M., Correa-Baena, J. P., Gratzel, M., Hagfeldt, A. & Abate, A. Perovskite Solar Cells: From the Atomic Level to Film Quality and Device Performance. Angewandte Chemie-International Edition 57, 2554-2569, doi:10.1002/anie.201703226 (2018).
94Guo, Y. et al. Enhancement in the efficiency of an organic–inorganic hybrid solar cell with a doped P3HT hole-transporting layer on a void-free perovskite active layer. Journal of Materials Chemistry A 2, 13827-13830 (2014).
95Yang, G., Tao, H., Qin, P. L., Ke, W. J. & Fang, G. J. Recent progress in electron transport layers for efficient perovskite solar cells. Journal of Materials Chemistry A 4, 3970-3990, doi:10.1039/c5ta09011c (2016).
96Gubbala, S., Chakrapani, V., Kumar, V. & Sunkara, M. K. Band‐Edge Engineered Hybrid Structures for Dye‐Sensitized Solar Cells Based on SnO2 Nanowires. Adv. Funct. Mater. 18, 2411-2418 (2008).
97Magne, C., Moehl, T., Urien, M., Grätzel, M. & Pauporte, T. Effects of ZnO film growth route and nanostructure on electron transport and recombination in dye-sensitized solar cells. Journal of Materials Chemistry A 1, 2079-2088 (2013).
98Mahmood, K., Swain, B. S. & Amassian, A. Double-layered ZnO nanostructures for efficient perovskite solar cells. Nanoscale 6, 14674-14678 (2014).
99Liu, D. & Kelly, T. L. Perovskite solar cells with a planar heterojunction structure prepared using room-temperature solution processing techniques. Nature Photonics 8, 133-138, doi:10.1038/nphoton.2013.342 (2013).
100Son, D.-Y., Im, J.-H., Kim, H.-S. & Park, N.-G. 11% efficient perovskite solar cell based on ZnO nanorods: an effective charge collection system. The Journal of Physical Chemistry C 118, 16567-16573 (2014).
101Cheng, Y. et al. Decomposition of organometal halide perovskite films on zinc oxide nanoparticles. ACS Appl. Mater. Interfaces 7, 19986-19993 (2015).
102You, J. et al. Improved air stability of perovskite solar cells via solution-processed metal oxide transport layers. Nature nanotechnology 11, 75 (2016).
103Tiwana, P., Docampo, P., Johnston, M. B., Snaith, H. J. & Herz, L. M. Electron mobility and injection dynamics in mesoporous ZnO, SnO2, and TiO2 films used in dye-sensitized solar cells. ACS nano 5, 5158-5166 (2011).
104Ke, W. et al. Effects of annealing temperature of tin oxide electron selective layers on the performance of perovskite solar cells. Journal of Materials Chemistry A 3, 24163-24168 (2015).
105Ke, W. J. et al. Low-Temperature Solution-Processed Tin Oxide as an Alternative Electron Transporting Layer for Efficient Perovskite Solar Cells. J. Am. Chem. Soc. 137, 6730-6733, doi:10.1021/jacs.5b01994 (2015).
106Anaraki, E. H. et al. Highly efficient and stable planar perovskite solar cells by solution-processed tin oxide. Energy & Environmental Science 9, 3128-3134 (2016).
107Jiang, Q. et al. Enhanced electron extraction using SnO 2 for high-efficiency planar-structure HC (NH 2) 2 PbI 3-based perovskite solar cells. Nature Energy 2, 16177 (2017).
108Kogo, A., Numata, Y., Ikegami, M. & Miyasaka, T. Nb2O5 blocking layer for high open-circuit voltage perovskite solar cells. Chem. Lett. 44, 829-830 (2015).
109Wang, K. et al. Low-temperature and solution-processed amorphous WO X as electron-selective layer for perovskite solar cells. The journal of physical chemistry letters 6, 755-759 (2015).
110Kim, B. J. et al. Highly efficient and bending durable perovskite solar cells: toward a wearable power source. Energy & Environmental Science 8, 916-921, doi:10.1039/c4ee02441a (2015).
111Qin, M. et al. Perovskite solar cells based on low-temperature processed indium oxide electron selective layers. ACS Appl. Mater. Interfaces 8, 8460-8466 (2016).
112Oh, L. S. et al. Zn2SnO4-based photoelectrodes for organolead halide perovskite solar cells. The Journal of Physical Chemistry C 118, 22991-22994 (2014).
113Ke, W. et al. Efficient planar perovskite solar cells using room-temperature vacuum-processed C 60 electron selective layers. Journal of Materials Chemistry A 3, 17971-17976 (2015).
114Ryu, S. et al. Fabrication of metal-oxide-free CH 3 NH 3 PbI 3 perovskite solar cells processed at low temperature. Journal of Materials Chemistry A 3, 3271-3275 (2015).
115Upama, M. B. et al. Role of fullerene electron transport layer on the morphology and optoelectronic properties of perovskite solar cells. Org. Electron. 50, 279-289 (2017).
116Sung, H. et al. Transparent Conductive Oxide‐Free Graphene‐Based Perovskite Solar Cells with over 17% Efficiency. Advanced Energy Materials 6 (2016).
117Lu, H., Sun, J., Zhang, H., Lu, S. & Choy, W. C. Room-temperature solution-processed and metal oxide-free nano-composite for the flexible transparent bottom electrode of perovskite solar cells. Nanoscale 8, 5946-5953 (2016).
118You, P., Liu, Z., Tai, Q., Liu, S. & Yan, F. Efficient semitransparent perovskite solar cells with graphene electrodes. Adv. Mater. 27, 3632-3638 (2015).
119Yan, K. et al. High‐Performance Graphene‐Based Hole Conductor‐Free Perovskite Solar Cells: Schottky Junction Enhanced Hole Extraction and Electron Blocking. Small 11, 2269-2274 (2015).
120Wang, J. T.-W. et al. Low-temperature processed electron collection layers of graphene/TiO2 nanocomposites in thin film perovskite solar cells. Nano Lett. 14, 724-730 (2013).
121Han, G. S. et al. Reduced graphene oxide/mesoporous TiO2 nanocomposite based perovskite solar cells. ACS Appl. Mater. Interfaces 7, 23521-23526 (2015).
122Zhu, Z. et al. Efficiency enhancement of perovskite solar cells through fast electron extraction: the role of graphene quantum dots. J. Am. Chem. Soc. 136, 3760-3763 (2014).
123Kuang, C. et al. Highly efficient electron transport obtained by doping PCBM with graphdiyne in planar-heterojunction perovskite solar cells. Nano Lett. 15, 2756-2762 (2015).
124Wu, Z. et al. Efficient planar heterojunction perovskite solar cells employing graphene oxide as hole conductor. Nanoscale 6, 10505-10510 (2014).
125Li, W. et al. Graphene oxide as dual functional interface modifier for improving wettability and retarding recombination in hybrid perovskite solar cells. Journal of Materials Chemistry A 2, 20105-20111 (2014).
126Ye, J., Li, X., Zhao, J., Mei, X. & Li, Q. Efficient and stable perovskite solar cells based on functional graphene-modified P3HT hole-transporting layer. RSC Advances 6, 36356-36361 (2016).
127Xiao, J. et al. Efficient CH3NH3PbI3 Perovskite Solar Cells Based on Graphdiyne (GD)‐Modified P3HT Hole‐Transporting Material. Advanced Energy Materials 5 (2015).
128Yeo, J.-S. et al. Highly efficient and stable planar perovskite solar cells with reduced graphene oxide nanosheets as electrode interlayer. Nano Energy 12, 96-104 (2015).
129Chen, W. et al. Black Phosphorus Quantum Dots for Hole Extraction of Typical Planar Hybrid Perovskite Solar Cells. The journal of physical chemistry letters 8, 591-598 (2017).
130Kim, Y. G. et al. Atomically thin two-dimensional materials as hole extraction layers in organolead halide perovskite photovoltaic cells. J. Power Sources 319, 1-8 (2016).
131Dai, R., Wang, Y., Wang, J. & Deng, X. Metal‐organic Compound Branched MoS2 for Achieving High Performance Perovskite Solar cells. ChemSusChem (2017).
132Cappel, U. B., Daeneke, T. & Bach, U. Oxygen-induced doping of spiro-MeOTAD in solid-state dye-sensitized solar cells and its impact on device performance. Nano Lett. 12, 4925-4931, doi:10.1021/nl302509q (2012).
133Marchioro, A. et al. Unravelling the mechanism of photoinduced charge transfer processes in lead iodide perovskite solar cells. Nature photonics 8, 250 (2014).
134Sum, T. C. & Mathews, N. Advancements in perovskite solar cells: photophysics behind the photovoltaics. Energy & Environmental Science 7, 2518-2534 (2014).
135Sun, S. et al. The origin of high efficiency in low-temperature solution-processable bilayer organometal halide hybrid solar cells. Energy & Environmental Science 7, 399-407 (2014).
136Tanaka, K. et al. Comparative study on the excitons in lead-halide-based perovskite-type crystals CH3NH3PbBr3 CH3NH3PbI3. Solid state communications 127, 619-623 (2003).
137Han, G. et al. Towards high efficiency thin film solar cells. Progress in Materials Science 87, 246-291 (2017).
138Hoppe, H. & Sariciftci, N. S. Organic solar cells: An overview. Journal of materials research 19, 1924-1945 (2004).
139Lidzey, D. Optical Spectroscopy, <https://www.slideshare.net/cdtpv/optical-spectroscopy-56823999> (2016).
140Fukuoka, H., Isami, T. & Yamanaka, S. Crystal structure of a layered perovskite niobate KCa2Nb3O10. J. Solid State Chem. 151, 40-45 (2000).
141Akatsuka, K., Takanashi, G., Ebina, Y., Haga, M. & Sasaki, T. Electronic Band Structure of Exfoliated Titanium- and/or Niobium-Based Oxide Nanosheets Probed by Electrochemical and Photoelectrochemical Measurements. Journal of Physical Chemistry C 116, 12426-12433, doi:10.1021/jp302417a (2012).
142Blancon, J.-C. et al. Extremely efficient internal exciton dissociation through edge states in layered 2D perovskites. Science, eaal4211 (2017).
143Cao, D. H., Stoumpos, C. C., Farha, O. K., Hupp, J. T. & Kanatzidis, M. G. 2D Homologous Perovskites as Light-Absorbing Materials for Solar Cell Applications. J. Am. Chem. Soc. 137, 7843-7850, doi:10.1021/jacs.5b03796 (2015).