Characterization of perovskite films for HTM-free solar cells

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics 2015 (HOPV15)

Poster, Vera La Ferrara, 379
Publication date: 5th February 2015

Organometal halide perovskites are promising candidates as high bandgap absorbers in multijunction solar cells. In recent years different architectures of cells have been investigated. Hole-conductor free configuration simplifies fabrication procedure and reduces manufacturing costs by removing one of the most expensive components of device. This makes it possible to achieve the solar cells based on hybrid lead halide perovskite in the low-cost photovoltaic devices [1, 2]. In this work sequential deposition has been applied to deposit CH₃NH₃PbI₃ films on fluorine doped tin oxide (FTO) covered with mesoporous TiO₂ (mTiO₂) of different thickness. In particular the effect of spinning rate during PbI₂ deposition, drying procedure and dipping time in a solution of CH₃NH₃I have been investigated for obtaining high performing devices. Substrate surface coverage and morphology have been investigated by scanning electron microscopy imaging and cross sections have been milled by a focused ion beam (FIB) in order to evaluate thickness of perovskite overlayer. In figure 1 typical cross sections of glass-FTO/mTiO2 used as starting substrate (fig.1a) and perovskite layers deposited changing process parameters (figs. 1b and 1c) resulting in different overlayer thickness are shown. Solar cells have been completed and consequently characterized without hole-transport material layers employing back contact with deep work function, such as gold, where the perovskite layer acts at the same time as absorber and hole conductor. First results show improvement of efficiency, short-circuit photocurrent density and voltage, using the same parameters of perovskite deposition but changing mesoporous TiO₂ thickness.
Fig.1: typical cross sections of glass-FTO/mTiO2 used as starting substrate (a) and perovskite layers deposited changing process parameters (b and c) resulting in different overlayer thickness
[1] Shi, J.; Dong, J.; Lv S.; Xu, Y.; Zhu, L.; Xiao J., Xu, X.; Wu, H.; Li, D.; Luo, Y.; Meng, Q. Hole-conductor-free perovskite organic lead iodide heterojunction thin-film solar cells: High efficiency and junction property. Applied Physics Letters 2014, 104, 063901-4 [2] Coen, B.-E.; Gamliel, S.; Etgar, L. Parameters influencing the deposition of methylammonium lead halide iodide in hole conductor free perovskite-based solar cells. APL Materials 2014, 2, 081502-8

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