Improved mixed-dimensional 3D/2D perovskite layer with formamidinium bromide salt for highly efficient and stable perovskite solar cells

Boosting the stability of perovskite solar cells (PSCs) is necessary to the industrialization of them. It is believed the dimensional engineering of the perovskite layer may tackle the low stability of PSCs. In this research, a 3D/2D heterostructure layer based on 4-Fluoro-Phenethylammonium iodide (4FPEAI) was successfully fabricated to improve the humidity resistance and the power conversion efficiency (PCE) of the 3D PSCs. After that, the research aims to boost the quality of the fabricated 3D/2D layer and further improving the photovoltaic performance and stability of devices. For this purpose, the formamidinium bromide (FABr) salt was introduced as an additive to the 2D precursor. The FABr additive treated the interfacial of the 3D/2D perovskite/HTL and significantly increased the charge transport processes in the PSCs. Results showed with 5% of FABr additive in a molar ratio, the PCE of 3D/2D PSCs raised to 21.79% from the 19.61% for the net 3D/2D PSCs. Besides, the humidity and irradiance stability of the PSCs dramatically were improved with the FABr modification of the 3D/2D perovskite layer. The suggested approach, i.e., modification of the 3D/2D layer to achieve a more desirable 3D/2D layer, may provide a practical step towards the PSC development.