Low-Toxicity Near-Infrared InP Quantum Dot Sensitized Solar Cells with Power Conversion Efficiency Exceeding 5%

Abstract Colloidal InP quantum dots (QDs) are promising near-infrared (NIR) materials for environmentally benign QD-sensitized solar cells (QDSCs). Yet previous studies on QDSCs have never been able to extend the light harvesting capability of InP QDs to NIR. In this work, InP QDs with an absorption onset reaching ∼750 nm were synthesized using low-reactivity indium(I) salts and phosphine precursors combined with NH4PF6-mediated in situ etching. Ligand exchange with 3-mercaptopropionic acid enabled high-density and uniform loading of these QDs on mesoporous TiO2 photoanodes. Through optimization of photoanode architecture and interfacial engineering, a record power conversion efficiency of 5.20% was achieved for InP-QDSCs. Transient absorption analysis reveals that device performance is primarily constrained by the small energetic driving force for electron injection from NIR InP QDs to TiO2, providing guidance for further development of high-efficiency InP-based QDSCs.