Highly Efficient and Stable Wide Band Gap Quasi-2D Perovskite Solar Cells via Interfacial Quantum Well Regulation

Quasi-2D perovskites are known for their long-term environmental stability. In this system, bulky spacers are expected to inhibit ion migration and reduce interfacial nonradiative recombination. However, it also presents challenges for charge transportation at the same time. As a result, the possibility and great potential of such quasi-2D perovskites for wide band gap (WBG) solar cells have rarely been explored. Here, we specialize in formamidinium-based quasi-2D WBG perovskites, obtaining a preferential crystal orientation perovskite film. To obtain better performance, the interfacial quantum wells (QWs) regulation strategy for a higher preference of a low-dimensional perovskite interface layer is proposed. The interfacial QWs are adjusted by the preference binding capacity of the solvent and long-chain molecules. The importance of interfacial QW distribution for charge transportation and stability is further investigated in this work. The quasi-2D 1.70 eV perovskite solar cells achieved by the regulation strategy exhibit an efficiency of 20.18% with a <i>V</i>_OC of 1.27 V and maintain 95% initial performance under 1 sun illumination over 500 h of stable operation.