Enhanced performance of planar perovskite solar cells using low-temperature processed Ga-doped TiO2 compact film as efficient electron-transport layer

Planar perovskite solar cells (PSCs) based on low-temperature processed gallium (Ga)-doped TiO2 (Ga-TiO2) films and CH3NH3PbI3-xClx active layer have been fabricated by one-step method. The annealing temperature of Ga-TiO2 electron-transport layer (ETL) is only 200 degrees C. The effect of Ga doping concentrations on the electric properties of Ga-TiO2 ETL and PSCs has been systematically investigated. At the optimum Ga concentration, the PSCs based on Ga-TiO2 and TiO2 ETL achieve the champion power conversion efficiency (PCE) of 17.09% and 14.63%, and an average PCE of 16.51% and 14.15%, respectively. The higher PCE of PSCs based on Ga-TiO2 ETL (Ga-PSCs) can be attributed to the reduced trap state density, enhanced conductivity, increased electron mobility and suppressed charge recombination, which will lead to higher V-oc, J(sc) and FF, thus the improved PCE. Moreover, the Ga-PSC shows negligible hysteresis and improved stability compared to the reference TiO2-PSC. After being stored in air for 28 days, the PCE of unsealed Ga-PSCs can remain to be 86% of its initial value. This work provides an excellent strategy to fabricate efficient and stable PSCs by low-temperature process. (C) 2018 Elsevier Ltd. All rights reserved.