Simultaneous Ligand Exchange Fabrication of Flexible Perovskite Solar Cells using Newly Synthesized Uniform Tin Oxide Quantum Dots

Halide perovskite solar cells (HPSCs) have a significant potential for future photovoltaic systems because of a high power conversion efficiency (PCE) exceeding 23% using solution processing methods. A low-temperature processed oxide layer is a challenging issue for large-scale manufacture of flexible and low-cost HPSCs. Here, we propose a simple reverse micelle-water injection method for highly dispersed ligand-capped ultrafine SnO₂ quantum dots (QD). Interestingly, we observed that the ligands, which help in the formation of a uniform SnO₂ QD thin film, spontaneously exchange for halide through a perovskite solution, and finally we form a suitable SnO₂ QD-halide junction for high-performance HPSCs. The flexible HPSC with the SnO₂ QD-halide junction formed via the ligand exchange exhibits a high PCE of 17.7% using a flexible substrate. It also shows an excellent flexibility, where the initial PCE is maintained within 92% after 1000 bending cycles with a bending radius of 18 mm.