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 PbSO 4 (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 PbSO 4 (PbO) 4 QDs significantly reduce the defect density of the as-prepared CH 3 NH 3 PbI 3 films by passivating under-coordinated Pb ions and I anions and effectively enhance charge extraction efficiency at the TiO 2 /CH 3 NH 3 PbI 3 and CH 3 NH 3 PbI 3 /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 CH 3 NH 3 PbI 3 /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 PbSO 4 (PbO) 4 QDs compared to that (16.86%) of the PSCs without OA-coated PbSO 4 (PbO) 4 , corresponding to a 18.7% enhancement. Moreover, the PSCs with OA-coated PbSO 4 (PbO) 4 QDs maintain 90% of initial efficiency after operation for 280 h, indicating better stability than the PSCs without PbSO 4 (PbO) 4 QDs.