Separation of Hoke and Schottky effects for improvement of mixed halide perovskite solar cell stability

TL;DR

This paper investigates ion migration effects in mixed halide perovskite solar cells, distinguishing Hoke and Schottky effects, and demonstrates how modifying transport layer thickness can significantly enhance device stability.

Contribution

It introduces a method to separate Hoke and Schottky effects in perovskite solar cells and shows that increasing transport layer thickness improves stability by blocking ion migration effects.

Findings

Schottky effect causes rapid charge-carrier separation loss

Hoke effect leads to slow defect accumulation and recombination

Thick transport layer increases T80 stability from 15 seconds to 60 minutes

Abstract

Ion migration in halide perovskites is a key factor limiting the operational stability of solar cells due to formation of halogen ion enriched domains and accumulation layers. The present work demonstrates the manifestation of ion migration in two ways via Hoke and Schottky effects. Both effects are induced by external exposure but have its peculiar way of solar cell performance degradation. We demonstrate the effects of ion migration on the device performance by measuring time dependent short-circuit current and different impedance characteristics that allow to see how charge-carrier separation property degrades. The Schottky effect leads to the rapid decrease of charge-carrier separation characteristic of solar cell while Hoke effect leads to the slow defect accumulation in the perovskite layer leading to the enhanced Shockley-Read-Hall recombination. Separation of these two effects can be realized by simple increase of transport layer thickness. A thick transport layer blocks losses of charge-carrier selectivity in a solar cell and leads to an enormous increase of T80 time, from 15 seconds up to 60 minutes.