Application Of Cuprous-Based Inorganic Hole-Transporting Materials And Defect Passivation Additives In Perovskite Solar Cells

Organic-inorganic hybrid halide perovskite has high molar extinction coefficient,low exciton binding energy,long carrier diffusion length,suitable tunable energy level and ease of fabrication,making perovskite solar cells(PSCs)the most promising alternative for the next generation of thin-film photovoltaics.By optimizing the perovskite composition,device structure and deposition method,the power conversion efficiency(PCE)of PSCs has been significantly increased from 3.8%in 2009 to the latest certified value of 25.2%,approaching the best performance of industry silicon solar cell efficiency.However,PSCs are still full of challenges in terms of charge transfer interface regulation,thin film defect passivation and device stability.This thesis mainly focuses on preparation methods of inorganic hole-transporting layer and passivation of defect on the perovskite film surface.In this thesis,a simple solid-gas reaction method was applied to prepare a denser and more uniform cuprous iodide film than spin-coating method.As the hole-transporting layer in inverted planar PSCs,it effectively prevented perovskite layer from direct contacting with the fluorine-doped tin oxide(FTO)substrate,greatly reducing the energy loss caused by the charge-carrier recombination at the interface.As result,overall performance of the devices was improved.PSCs prepared by this method exhibited a decent PCE of 14.71%,with good repeatability,negligible hysteresis and decent stability.This is one of the highest PCE values reported at that time for CuI-based PSCs.Cuprous thiocyanate(CuSCN)serving as crystallization inhibitor of CuI was employed to improve the quality of cuprous iodide film prepared by solution processing.And a dense and uniform composite film was successfully applied to inverted planar PSCs.The CuI/CuSCN composites combined the advantageous properties of their parental materials,i.e.,high electrical conductivity and good film morphology.As a consequence,the champion PSC device based on the composite CuI/CuSCN HTL yielded a PCE of 18.76%,surpassing the corresponding values of the respective devices with pristine CuI(14.53%)and CuSCN(16.66%).This value is among the top efficiencies reported thus far for CuI-and CuSCN-based inverted planar PSCs.Natural chlorophyll derivative chlorophyll copper sodium salt(NaCu-Chl)was introduced as a defect passivation material on the surface of the perovskite film.This passivation strategy was successfully applied to prepare efficient and stable PSCs.NaCu-Chl anchoring on perovskite film surface by functional group-COO-,passvated undercoordinated Pb2+ sites through coordinate or ionic interaction,reducing the non-radiative recombination sites on the film surface.As a result,NaCu-Chl-treated PSCs delivered a PCE of 20.27%,and undesired hysteresis was largely suppressed.Furthermore,the hydrophobicity of NaCu-Chl also improved the stability of devices in a humid environment.