Optimization Of ZnO Electron Transport Layer In PbS Quantum Dot Solar Cells

Lead sulfide(PbS)colloidal quantum dot(CQD)solar cells have received extensive research attention in recent years due to their wide spectral response,excellent stability,and solution-process fabrication.Zinc oxide(ZnO)nanoparticles(NPs)are commonly used as electron transport layer(ETL)materials for PbS CQD solar cells due to their lowtemperature solution-process synthesis,high conductivity and transparency.However,the intrinsic defects in ZnO,such as surface hydroxyl groups and oxygen vacancies,can easily lead to carrier recombination,limiting the carrier transport performance of ZnO.Therefore,exploring effective passivation methods for ZnO is crucial to improve the device photovoltaic performance.In this thesis,we aim at the ETL of PbS CQD solar cells,investigating the influence of different ZnO modification strategies on their optoelectronic properties,and applying them to the preparation of high-performance PbS quantum dot solar cells.Chapter 1:A brief introduction to the background of ETL in PbS CQD solar cell,including the basic theory,characterizations of PbS CQD solar cells,the recently development of PbS CQD solar cells,the basic theory and fabrication of solar cell ETL,and the research progress of ETL in PbS CQD solar cells.Chapter 2:Open-shell diradical-sensitized ZnO for high-performance CQD solar cells.Due to the special electron transfer tendency of diradical molecules,electrons tend to transfer from diradical molecules to ZnO trap states.The transferred electrons can fill in the trap states of ZnO.After the filling of traps,ZnO show improved electron transfer property and better charge extract ability.We use sensitized ZnO to fabricate PbS CQD solar cells,and achieving a PCE of 13.54%,which is the highest PCE of direct synthesized PbS solar cells.This work provides a simple and efficient method for improving the property of solar cell ETLs.At the same time,the electron donor ability and the energy level of open-shell diradical molecules can be easily modified by adjusting the structure of molecules,which means this work will inspire the further application of diradical molecules in solar cells.Chapter 3:TMS-Cl decorated ZnO for high-performance CQD solar cells.The bonding of Cl and Zn can efficiently reduce the traps of ZnO.By dip-coating ZnO film in TMS-Cl solution,we achieve the Cl decorated ZnO.The optimized ZnO QDs generate a new intragap,and the electron extracting ability can be improved.We used the optimized ZnO to fabricate solar cells and achieve a PCE of 13.02%.This method can be easily conducted and will provide a new direction for the study of ETL in PbS CQD solar cells.In summary,we have conducted a series of explorations on the passivation of ZnO as an ETL for PbS CQD solar cells and carefully investigate the impact of ZnO’s optoelectronic properties on the photovoltaic performance of solar cells.The research results of this paper may further promote the development of PbS CQD solar cells.