title: Vacuum-assisted thermal annealing of CH3NH3PbI3 for highly stable and efficient perovskite solar cells.
abstract: Solar cells incorporating lead halide-based perovskite absorbers can exhibit impressive power conversion efficiencies (PCEs), recently surpassing 15%. Despite rapid developments, achieving precise control over the morphologies of the perovskite films (minimizing pore formation) and enhanced stability and reproducibility of the devices remain challenging, both of which are necessary for further advancements. Here we demonstrate vacuum-assisted thermal annealing as an effective means for controlling the composition and morphology of the CH(3)NH(3)PbI(3) films formed from the precursors of PbCl(2) and CH(3)NH(3)I. We identify the critical role played by the byproduct of CH(3)NH(3)Cl on the formation and the photovoltaic performance of the perovskite film. By completely removing the byproduct through our vacuum-assisted thermal annealing approach, we are able to produce pure, pore-free planar CH(3)NH(3)PbI(3) films with high PCE reaching 14.5% in solar cell device. Importantly, the removal of CH(3)NH(3)Cl significantly improves the device stability and reproducibility with a standard deviation of only 0.92% in PCE as well as strongly reducing the photocurrent hysteresis.
authors.affiliation: Department of Electrical and Electronic Engineering, The University of Hong Kong , Pok Fu Lam Road, Hong Kong, China.
authors.forename: Feng Xian
authors.initials: FX
authors.lastname: Xie
authors.forename: Di
authors.initials: D
authors.lastname: Zhang
authors.forename: Huimin
authors.initials: H
authors.lastname: Su
authors.forename: Xingang
authors.initials: X
authors.lastname: Ren
authors.forename: Kam Sing
authors.initials: KS
authors.lastname: Wong
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
authors.forename: Wallace C H
authors.initials: WC
authors.lastname: Choy
keywords: CH3NH3Cl; crystallization process; morphology; perovskite solar cell; vacuum-assisted thermal annealing