Healing the defects in CsPbI3 solar cells by CsPbBr3 quantum dots

Cesium lead iodide (CsPbI3) 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 CsPbI3 films especially at the grain boundaries (GBs), which limit the power conversion efficiency (PCE) of CsPbI3 solar cells. in this work, we introduced CsPbBr3 quantum dots (QDs) on top of the CsPbI3 film to passivate the defects. As CsPbBr3 QDs have a small size and a similar crystal structure as the CsPbI3, they are excellent modifiers to fill in the GBs and heal the defects. Moreover, we find there is an anion exchange reaction between the CsPbBr3 QDs and CsPbI3 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 CsPbBr3 QDs increase the hydrophobicity of the films. As a result, the QDs treated CsPbI3 solar cells prepared at high temperature obtain PCEs exceeding 16% with high stability.

Automated summary

In this study, defects at the grain boundaries of solution processed CsPbI3 films were effectively repaired by introducing CsPbBr3 quantum dots. The treated CsPbI3 solar cells showed enhanced carrier lifetime, reduced defect density, and achieved power conversion efficiencies exceeding 16% when prepared at high temperature.