Exploration of polymer-assisted crystallization kinetics in CsPbBr3 all-inorganic solar cell

Abstract

• The compact CsPbBr 3 layer with pure phase was obtained. • The PCE of 7.8% is the highest efficiency of CsPbBr 3 based device via one step process. • The tandem solar cells present no degradation after 120 h UV aging test. All-inorganic perovskite material (CsPbBr 3 ) has attracted enormous attention in photovoltaic devices due to superior stability. However, the thickness of CsPbBr 3 film beyond 100 nm suffers from poor morphology, impurity phase and defects due to unbalance between fast growth and slow nucleation of film. Here, we introduce polyethylene glycol (PEG) into solution to achieve compact CsPbBr 3 film with pure phase via a simple one-step solution process. The Lewis base of PEG interacts with the Lewis acid of Pb 2+ to reduce the cluster size of CsBr-PbBr 2 -DMSO colloids as well as to increase the nucleation rate. The CsPbBr 3 film magnitude less in intrinsic defect concentration is obtained by the addition of PEG. The open-circuit voltage increases from 1.15 eV to 1.41 eV with the highest efficiency of 7.8% as a result of less charge recombination of device, which is the highest efficiency ever recorded in one step solution process. The current–voltage curves measured at five different positions of large size device based on PEG (100 mm 2 ) were almost identical, indicating highly uniform of devices. Thanks to the high quality of PEG modified CsPbBr 3 film, there is no efficiency reduction during 120 h UV illumination. It was further used as a UV filter in tandem device which effectively restricts the UV degradation of bottom organic-inorganic perovskite solar cell. The tandem solar cell still remains 93% of the initial PCE after 120 h UV aging test, which are the main routes for commercializing device.