High-Performance Electron-Transport-Layer-Free Quantum Junction Solar Cells with Improved Efficiency Exceeding 10%

Colloidal quantum dot solar cells (CQDSCs) are good candidates for low-cost power generators, due to their wide light-response range, high theoretical efficiency, and solution processability. Nevertheless, the generally used metal oxide electron transport layer (MOETL) induced various problems, blocking the performance enhancement of CQDSCs, such as band alignment mismatch, high-energy photon loss, and photoinduced interfacial degradation. In the work described herein, we constructed high-efficiency and air-stable MOETL-free solar cells based on quantum junction device structure, through manipulating the semiconductor and surface-trap properties of PbS CQDs by ligand engineering. A record power conversion efficiency of 10.5% was successfully achieved in our MOETL-free quantum junction solar cells (QJSCs). Increased photogenerated current density was obtained in MOETL-free QJSCs because of the ultraviolet and near-infrared photoresponse enhancement. These unencapsulated MOETL-free QJSCs show long-term air-storage stability (>4000 h). Our work successfully demonstrates the MOETL-free quantum junction as a high-efficiency and stable structure for solar cells, paving a way for application of CQDSCs in the full-spectrum, scalable-production, portable, and flexible photovoltaic technology.