Organic Ligand-Free ZnO Quantum Dots for Efficient and Stable Perovskite Solar Cells

摘要

Zinc oxide (ZnO) is a promising electron-transport layer (ETL) in thin-filmphotovoltaics. However, the poor chemical compatibility between commonlyused sol–gel-derived ZnO nanostructures and organo–metal halide perovskitesmakes it highly challenging to obtain efficient and stable perovskitesolar cells (PSCs). Here, a novel approach is reported for low-temperatureprocessed pure ZnO ETLs for planar heterojunction PSCs based on ZnOquantum dots (QDs) stabilized by dimethyl sulfoxide (DMSO) as easilyremovable solvent molecules. With no need for the ETL doping or surfacemodification, the champion PSC comprising the mixed-cation and mixedhalideCs_5(MA_(0.17)FA_(0.83))_(95)Pb(I_(0.83)Br_(0.17))_3 absorber layer reaches a maximumpower conversion efficiency of 20.05%, which is significantly higher thanthat obtained for a reference device based on a standard sol–gel-derived ZnOnanostructured layer (17.78%). Thus, along with the observed better operationalstability in ambient conditions and elevated temperature, the championdevice achieves the state-of-the-art performance among reported non-passivatedpure ZnO ETL-based PSCs. The improved photovoltaic performance isattributed to both a higher uniformity of the surface morphology and a lowerdefects density of films based on the organometallic-derived QDs that arelikely to ensure the enhanced stability of the ZnO/perovskite interface.