Enhanced charge dynamics via V-doped SnO2 combined with interface functionalization for perovskite solar cells

Tin oxide (SnO2) as a promising alternative material to TiO2 has been widely used in perovskite solar cells. Metal-doping will optimize the SnO2 films and further improve the device performance. The vanadium-doped SnO2 (V-SnO2) can highly enhance the carrier concentration and electrical conductivity, but the surface hydroxyl groups will result in abundant defect states. Some molecules with functional groups have been used to passivate interface traps. Metformin and urea were incorporated into the V-SnO2 films, and the NH2 groups will interact with SnO2 and perovskite to passivate interface traps. The metformin shows the stronger interactions between NH2 groups and SnO2 crystals than urea. Moreover, the diblock polymer of (PEO)150-(PPO)20 was incorporated into the polycrystalline (FA0.90MA0.10)0.92Cs0.08Pb(I0.98Br0.02)3 perovskite films to passivate defects at the grain boundaries and improve the stability. Under the synergistic effects of improved conductivity and interfacial functionalization, the best-performing device exhibits a high photoelectric conversion efficiency of 22.87% (a VOC of 1.157 V, a JSC of 24.37 mA cm−2, and an FF of 0.811). The charge recombination kinetics and transport dynamics are discussed by different detection techniques.