Carbon Quantum Dot-Passivated Perovskite/Carbon Electrodes for Stable Solar Cells

Carbon-based perovskite solar cells (C-PSCs) have been extensively researched as alternatives to fabricate cost-effective energy conversion devices. The interface of the perovskite film and the carbon electrode is crucial for achieving good photovoltaic performance. Herein, two carbon quantum dots (CQDs) with different functional groups designated as A-CQDs and CA-CQDs are used to passivate the perovskite CH3NH3PbI3 surface, respectively. The surface ligand effect arising from the two CQDs is extensively investigated. The introduction of the A-CQDs passivation layer not only forms large crystal grains and decreases the defect density of the perovskite film but also well adjusts the energy level matching of the perovskite film and the carbon electrode, thereby promoting efficient carrier transfer. The C-PSC passivated by the A-CQDs film shows an improved photovoltaic property with a champion power conversion efficiency (PCE) of 13.97%. PCEs of the control PSCs and PSCs based on the CA-CQDs layer are 11.29% and 10.77%, respectively. Furthermore, A-CQDs-based C-PSCs retain more than 80% of their initial PCE under testing conditions of 35% humidity for 840 h of storage.