Healing the defects in CsPbI3 solar cells by CsPbBr3 quantum dots

Cesium lead iodide (CsPbl 3 ) is a promising photo-absorber for perovskite photovoltaics due to its high thermal stability and relatively small bandgap. However, there are many defects in solution processed polycrystalline CsPbl 3 films especially at the grain boundaries (GBs), which limit the power conversion efficiency (PCE) of CsPbl 3 solar cells. in this work, we introduced CsPbBr 3 quantum dots (QDs) on top of the CsPbl 3 film to passivate the defects. As CsPbBr 3 QDs have a small size and a similar crystal structure as the CsPbl 3 , they are excellent modifiers to fill in the GBs and heal the defects. Moreover, we find there is an anion exchange reaction between the CsPbBr 3 QDs and CsPbl 3 films, which is evidenced by photoluminescence spectra and grazing incidence X-ray diffraction patterns. The QDs treated films show enhanced carrier lifetime and reduced defect density. Additionally, the ligands on CsPbBr 3 QDs increase the hydrophobicity of the films. As a result, the QDs treated CsPbl 3 solar cells prepared at high temperature obtain PCEs exceeding 16% with high stability.