Preparation And Performance Optimization Of TiO₂ Electron Transport Layers For Perovskite Solar Cell

Perovskite solar cells?PSCs?have been widely studied in the field of solar energy conversion due to advantages such as high conversion efficiency,easy preparation and relatively low cost.The electron transport layer?ETL?is an important part of the PSCs,being used for electronic collection and influencing the quality of perovskite.Hence,preparing an electronic transport layer with appropriate wettability,morphology,and conduction band position is the effective way to improve the photoelectric conversion efficiency of perovskite solar cells.In this thesis,we focus on the preparation and performance optimization of TiO₂ ETLs for high efficiency perovskite solar cells.The main work is introduced as follows:1.We prepare dense TiO₂ thin film with smooth surface and good transparency by the spray pyrolysis method,and fabricate CH3NH3PbI3 perovskite solar cells by the so-called two-step method using the thin film as ETLs,and spiro-OMeTAD as hole transport layer.By optimizing TiO₂ film thickness,we obtain a modest photoelectric conversion efficiency of 5%.Surface wettability measurements show that the precursor solution of CH3NH3PbI3 perovskite spreads poorly on the smooth TiO₂ ETLs,which has a negative impact on the film quality and light absorption of perovskite layer and the efficiency of devices.2.In order to improve the wettability of TiO₂ ETLs,we develop a new type of nanoparticle ETLs by spin-coating from a commercial TiO₂?6 nm?colloidal suspension.The film has good transparency,but more importantly good wettability for the precursor solution of perovskite due to its considerable surface roughness.The perovskite solar cells,prepared with the new TiO₂ ETLs perform much better than those with sprayed ETLs.The highest efficiency is 9.13% by optimizing the morphology and thickness of the films.3.Further we try to improve the electron transport property of nanoparticle ETLs by the necking strategy.By simple spin-coating of TiCl₄ solution on the nanoparticle ETLs,the resistance of ETLs is reduced significantly.As a result,the short-circuit photocurrent is increased and solar energy conversion efficiency of perovskite devices is improved further to 10.63%.