Interface Modification by Ionic Liquid: A Promising Candidate for Indoor Light Harvesting and Stability Improvement of Planar Perovskite Solar Cells
Meng Li,a Chao Zhao,b Zhao-Kui Wang,a,* Cong-Cong Zhang,a Harrison K. H. Lee,b Adam Pockett,b Jérémy Barbé,b Wing Chung Tsoi,b Ying-Guo Yang,c Matthew J. Carnie,b Xing-Yu Gao,c Wen-Xing Yang,d James R. Durrant,d Liang-Sheng Liao,a,* and Sagar M. Jain*,b
Organic-inorganic hybrid perovskite solar cells (PSCs) are currently attracting significant interest owing to their promising outdoor performance. However, the ability of indoor light harvesting of the perovskites and corresponding device performance are rarely reported. Here, the potential of planar PSCs in harvesting indoor light for low-power consumption devices is investigated. Ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) is employed as a modification layer of [6,6]-phenyl-C61-butyric acid methyl ester) (PCBM) in the inverted PSCs. The incorporation of [BMIM]BF4 not only paves the interface contact between PCBM and electrode, but also facilitates the electron transport and extraction owing to the efficient passivation of the surface trap states. Moreover, [BMIM]BF4 with excellent thermal stability can act as a protective layer by preventing the erosion of moisture and oxygen into the perovskite layer. The resulting devices present a record indoor power conversion efficiency (PCE) of 35.20% under fluorescent lamps of 1000 lux, and an impressive PCE of 19.30% under 1 sun illumination. The finding in this work verifies the excellent indoor performance of PSCs to meet the requirements of eco-friendly economy.