Electronic defect passivation of FASnI3 films by simultaneous Hydrogen-bonding and chlorine co-ordination for highly efficient and stable perovskite solar cells

Tin based perovskite solar cells (Sn-PSCs) has emerged as a viable solution for the fabrication of low toxic PSCs. However, the rapid crystallization process of tin halide perovskite compounds often result in severe elctronic defects which limits the open circuit voltage (VOC) of the overall PSC. In this work, we report on the successful implementation of a bifunctional compound- Hydroxylamine Hydrochloride (HaHc) with FASnI3 perovksite to reduce the electronic defects. The hydroxyl group in the HaHc formed a hydrogen bond with iodide ion in FASnI3 perovskite system and stabilizes the overall structure, which is evidenced by nuclear magnetic resonance spectroscopy and first-principle calculations. Additionally, the Cl- ion of the HaHc co-ordinates with the under coordinated Sn2+ ions of the FASnI3 perovskite and induces crystal growth along the < h00 > direction with enhanced crystallinity. Collectively with these dual aspects, the HaHc reduces the electronic defects of the FASnI3 perovskite film. With an optimized concentration of HaHc added with the FASnI3, the corresponding Sn-PSCs showed improved VOC up to 0.676 V and power conversion efficiency of 9.18%. Additionaly, the bi-functional HaHc is effective to stabilize the FASnI3 system and exhibited light soaking stablity up to 500 h for the respective Sn-PSCs.