Facilitating the formation of SnO2 film via hydroxyl groups for efficient perovskite solar cells

Interfacial engineering has been considered as an effective technique to improve the photovoltaic performance of perovskite solar cells (PSCs). Here, the interface between tin oxide (SnO2) film and fluorine-doped tin oxide (FTO) glass is dealt with a piranha solution, resulting in more hydroxyl groups on the surface of FTO glass. SnO2 film is fabricated by spin-coating SnCl2·2H2O precursor. Our results demonstrate that SnO2 film exhibits high electrical conductivity, low electron trap density, and suitable energy level. Furthermore, SnO2 film with low roughness is beneficial to fabricate high-quality perovskite film. Then, the PSCs with the structure of FTO/SnO2/Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3/Spiro-OMeTAD/Au are also fabricated. The highest power conversion efficiency (PCE) of PSCs increases from 18.28% to 19.51%, and the average PCE enhances from 17.82% to 18.89%. The optimized PSC shows the long-term stability and remains 97% of its initial PCE after 4000 h on-shelf lifetime test.