Efficient Hybrid Solar Cells Based On Organic-inorganic Perovskites

Hybrid organic/inorganic halide perovskites have attracted significant attention owing to the very rapid progress in their photovoltaic properties over mere five years. The power conversion efficiency(PCE) has been increased from 3.8% in 2009 to 9.7% in 2012, and most recently to 19.3%. Thus far, much of the effort has focused on the fabrication of high-performance perovskite solar cells based on CH3NH3 Pb I3. However, until now, studies on the degradation mechanisms of organic/inorganic halide structures have been limited and methods to improve the stability are not well understood, but the stability is the most important aspect of practical application of the perovskite solar cells. We tried to fabricate the perovskite solar cells with high performance by different methods, and studied the inherent reason of the instability of perovskite solar cells in humidity or light. Then, different interface modifications were used to solution this question.Firstly, the perovskite solar cells with the plane structure of FTO/TiO2/CH3NH3PbI3/HTM/Ag were fabricated by different deposition method of CH3NH3PbI3, the maximun efficiency was 15.8%. The influence of the ZnO compact layer to the efficiency of perovskite solar cell was investigated. ALD-ZnO film deposited at low temperature was replaced the conventionally used compact TiO2 layer sintered at high temperature, and have successfully fabricated an ALD-ZnO-based perovskite solar cell with a high PCE of 13.1% by single step with a precursor containing PbI2 and CH3NH3 I. The devices on ZnO compact film using ALD method has equal photoelectrical conversion efficiency to those based on TiO2 compact layer. In addition, we found that the ALD-compact ZnO layer can promote the single step formation of CH3NH3PbI3 with a precursor containing chloridion at room temperature, but this had a negative impact on the performance of the resulting perovskite solar cells.Secondly, the humidity stability of perovskite solar cell was investigated. We used molecular structure modeling to explain the degradation mechanisms of organic/inorganic hybrid structures, and the calculations suggested that the organic/inorganic structure would inevitably change in a humidity environment. Therefore, to inhibit degradation of the perovskite solar cells in a humidity environment, we used the ALD method to deposit ultrathin Al2O3 films on the HTM layer. Remarkably, the PCE of the solar cell with ALD-Al2O3 retained ~90% of its initial value after 24 days storage in air.Lastly, the stability of perovskite solar cell under illumination was investigated. The degradation mechanism of perovskite solar cells under illumination in N2 was studied, it was concluded that the presence of the H2 O and O2 adsorbed onto the TiO2 substrate and the photocatalytic activity of TiO2 are the primary reason for the decomposition of CH3NH3PbI3 in perovskite solar cells under illumination. We fabricated perovskite solar cells post-modified by monolayer HOOC-R-NH3+Cl– exhibit improved stability under illumination.This thesis verified that ALD can uesd to fabricated the compact laey in the perovskite solar cell, and the interface post-modify can effectively improve the stability of the perovskite solar cells under humidity and illumination. Those will provide suggestions to the commercialization research of the perovskite solar cells.