Optimizing Surface Passivation of n-Type Quantum Dots for Efficient PbS Quantum Dot Solar Cells

The n-type quantum dot (QD) active layer is the core component of lead sulfide QD solar cells (PbS QDSCs). In the state-of-the-art PbS QDSCs, the active layer is commonly obtained through liquid-phase ligand exchange (LPLE). Due to the intricate chemical state of the ligand exchange solution providing halide ligand, therefore, the PbS-OAQD solutions is used at concentrations of 20, 30, and 40 mg mL-1 for LPLE, aiming to investigate the reasons for different surface states post-exchange and their impact on device performance. The results indicate that when the concentration of the PbS-OA QD solution is 30 mg mL-1, the exchanged QDs exhibit complete removal of surface OA, a higher content of short-chain ligand PbX2 (X = I, Br), Consequently, devices fabricated using PbS-PbX2 QD obtained through the exchange of 30 mg mL-1 PbS-OA QD solution achieve a higher power conversion efficiency (PCE) of 12.53%. This study presents a simple and effective strategy to enhance the performance of PbS QDSCs. This study reveals the differences in the surface states of PbS-PbX2 quantum dots obtained through liquid-phase ligand exchange using PbS-OA solutions of different concentrations. It explores the reasons for the formation of these surface states and investigates the impact of different surface states on the photovoltaic parameters of the devices.image (c) 2024 WILEY-VCH GmbH