Preparation And Photovoltaic Performance Of Perovskite Solar Cells Based On CdS Electron Transporting Layer

Organic-inorganic hybrid metal halide perovskite materials have become one of thehot research materials in the field of optoelectronics due to their adjustable band gap,high absorption coefficient and long carrier diffusion length.At present,the power conversion efficiency（PCE）of perovskite solar cells（PSCs）based on perovskite materials has reached 25.5%.As an important part of PSCs,the electron transporting layer（ETL）plays an important role in PSCs which could influence the performance of PSCs.Cadmium sulfide（CdS）semiconductor has the advantages of high electron mobility,suitable energy band,low photocatalytic activity and low temperature preparation,making it an excellent electron transporting material in PSCs.However,the performance of CdS-based PSCs is not ideal,which hinders the development of CdS-based PSCs.In this paper,two different methods,which are constructing electron transport bilayer and the modifying interface to obtain high-performance CdS-based PSCs,were explored to improve the interfacial electronic extraction of CdS-based ETL/perovskite and thus improve the performance of PSCs.The main research contents are summarized as follows:（1）The effect of TiO₂/CdS bilayer constructed on the photovoltaic performance of PSCs was studied.In this experiment,the CdS ETL ultra-thin films were prepared by chemical bath deposition（CBD）,and the TiO₂ films was introduced between the FTO conductive substrate and the CdS film to construct the TiO₂/CdS bilayer.The morphology,optics and electrical characteristics reveal that the TiO₂/CdS bilayer has the following positive effects:the presence of the TiO₂ underlayer avoids the incomplete coverage of CdS on the surface of FTO substrate.And the subsequently deposited perovskite layer has a significant increase in grain size.TiO₂,CdS and CH₃NH₃Pb I₃ form cascading energy level arrangement,which accelerates electron transfer from perovskite layer to ETLs.Finally,the electron extraction and charge recombination at the ETL/perovskite interface is enhanced and inhibited.The PCE of PSCs based on TiO₂/CdS bilayer is 15.11%,which is much higher than that of CdS-based PSCs（7.77%）.（2）The significance of PCBM modified CdS ETL surface on the photovoltaic performance of PSCs was studied.In this experiment,the surface of CdS thin film deposited by CBD was modified by PCBM.The results show that the introduction of PCBM reduces the surface roughness of CdS and reduces the leakage current between ETL and perovskite.At the same time,modification of PCBM improved the interface contact between CdS and perovskite layer,and inhibited the interface charge recombination.Finally,due to enhanced electron extraction and reduced charge recombination at the ETL/CH₃NH₃Pb I₃ interface,the PCE of PSCs based on CdS modified by PCBM was significantly improved（15.88%）.