Removing Leakage and Surface Recombination in Planar Perovskite Solar Cells

TL;DR

This paper demonstrates a significant reduction in leakage and surface recombination in planar perovskite solar cells by replacing PEDOT:PSS with polyarylamine, leading to improved performance under low light and reduced recombination losses.

Contribution

The study introduces the use of polyarylamine as a hole transport layer to effectively eliminate shunt pathways and surface recombination in perovskite solar cells, enhancing their efficiency and stability.

Findings

Three-order reduction of shunt loss with polyarylamine

Operation under moonlight irradiance with 530 mV VOC

Substantial minimization of surface recombination losses

Abstract

Thin-film solar cells suffer from various types of recombination, of which leakage current usually dominates at lower voltages. Herein, we demonstrate first a three-order reduction of the shunt loss mechanism in planar methylammonium lead iodide perovskite solar cells by replacing the commonly used hole transport layer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with a better hole-selective polyarylamine. As a result, these cells exhibit superior operation under reduced light conditions, which we demonstrate for the extreme case of moonlight irradiance, at which open-circuit voltages of 530 mV can still be obtained. By the shunt removal we also observe the VOC to drop to zero after as long as 2 h after the light has been switched off. Second, at higher illumination intensities the dominant losses in the PEDOT:PSS-based cell are ascribed to surface recombination and are also proven to be substantially minimized by instead employing the polyarylamine. We attribute the reduced shunt and surface recombination to the far better suited semiconductor character of the polyarylamine, compared to that of PEDOT:PSS, efficiently blocking electrons from recombining at this electrode.