Hydrophobic-Hydrophilic Block Copolymer Mediated Tuning of Halide Perovskite Photosensitive Device Stability and Efficiency

The polymer additive strategy provides a facile and cost-effectiveway for passivating defects and trap sites at the grain boundariesand interfaces and acting as a barrier against the external degradationfactors in perovskite-based devices. However, limited literature existsdiscussing the integration of hydrophobic and hydrophilic polymeradditives in the form of a copolymer within the perovskite films.The inherent difference in the chemical structure of these polymersand their interaction with perovskite components and the environmentleads to critical differences in the respective polymer-perovskitefilms. The current work utilizes both homopolymer and copolymer strategiesto understand the effect of polystyrene (PS) and polyethylene glycol(PEG), two common commodity polymers, over the physicochemical andelectro-optical properties of the as-fabricated devices and the distributionof polymer chains across the depth of perovskite films. The hydrophobicPS integrated perovskite devices PS-MAPbI(3), 36 PS-b-1.4-PEG-MAPbI(3), and 21.5 PS-b-20-PEG-MAPbI(3) outperform hydrophilic PEG-MAPbI(3) and pristine MAPbI(3) devices and exhibit higherphotocurrent, lower dark currents, and greater stability. A criticaldifference is also observed in the stability of devices, where rapiddecay of performance is observed in the pristine MAPbI(3) films. The deterioration in performance is highly limited for hydrophobicpolymer-MAPbI(3) films as they maintain 80% of their initialperformance.

Automated summary

The polymer additive strategy is a convenient and cost-effective way to improve the performance and stability of perovskite-based devices. However, the integration of different polymer additives in perovskite films has not been extensively studied. In this work, the effect of polystyrene (PS) and polyethylene glycol (PEG) on the physicochemical and electro-optical properties of perovskite devices was investigated, and it was found that hydrophobic PS integrated devices exhibited better performance and stability compared to hydrophilic PEG integrated devices.