Efficient and stable perovskite solar cells thanks to dual functions of oleyl amine-coated PbSO4(PbO)4 quantum dots: Defect passivation and moisture/oxygen blocking

The defects in perovskite crystals and the penetration of moisture/oxygen into the perovskite layer are major problems for perovskite solar cells (PSCs) to achieve long-term stability and high power conversion efficiency (PCE). However, there is still a lack of multifunctional passivation materials to solve these problems. Herein, for the first time, we report oleyl amine-coated PbSO4(PbO)4 quantum-dots (QDs), as a passivation material with dual functions to simultaneously passivate the surface defects and block the penetration of moisture/oxygen into the perovskite layer for stable and efficient PSCs. The PbSO4(PbO)4 QDs significantly reduce the defect density of the as-prepared CH3NH3PbI3 films by passivating under-coordinated Pb ions and I anions and effectively enhance charge extraction efficiency at the TiO2/CH3NH3PbI3 and CH3NH3PbI3/spiro-OMeTAD interfaces. Moreover, the hydrogen bond between H atoms of the OA and I atoms of the perovskite and the interface electric field at CH3NH3PbI3/OA interface also contribute to the improvement of efficiency and stability of PSCs. Finally, higher PCE (20.02%) is achieved by the PSCs with OA-coated PbSO4(PbO)4 QDs compared to that (16.86%) of the PSCs without OA-coated PbSO4(PbO)4, corresponding to a 18.7% enhancement. Moreover, the PSCs with OA-coated PbSO4(PbO)4 QDs maintain 90% of initial efficiency after operation for 280 h, indicating better stability than the PSCs without PbSO4(PbO)4 QDs.