Enhanced electronic properties in mesoporous TiO2 via lithium doping for high-efficiency perovskite solar cells

Perovskite solar cells are one of the most promising photovoltaic technologies with their extraordinary progress in efficiency and the simple processes required to produce them. However, the frequent presence of a pronounced hysteresis in the current voltage characteristic of these devices arises concerns on the intrinsic stability of organo-metal halides, challenging the reliability of technology itself. Here, we show that n-doping of mesoporous TiO2 is accomplished by facile post treatment of the films with lithium salts. We demonstrate that the Li-doped TiO2 electrodes exhibit superior electronic properties, by reducing electronic trap states enabling faster electron transport. Perovskite solar cells prepared using the Li-doped films as scaffold to host the CH3NH3PbI3 light harvester produce substantially higher performances compared with undoped electrodes, improving the power conversion efficiency from 17 to over 19% with negligible hysteretic behaviour (lower than 0.3%).
Perovskite solar cells are still plagued by hysteresis, despite the good charge transport properties of the perovskite counterpart. Here, the authors dope the mesoporous TiO2 scaffold with lithium to improve the transport properties of this other important component of solar cells, and reduce the hysteresis.