# Inverted J–V Hysteresis in Perovskite Solar Cells: Insights from Photovoltaic Quantum Efficiency

## TL;DR

This paper explains why perovskite solar cells show different performance when voltage is scanned forward or backward, linking it to ionic effects and recombination.

## Contribution

The study identifies the cause of inverted hysteresis in perovskite solar cells through EQE analysis and simulations.

## Key findings

- Inverted hysteresis is caused by blue-range photocurrent losses due to ionic accumulation and interface recombination.
- Ionic losses are bidirectional and affect charge collection efficiency depending on ionic distribution.
- The findings apply to various PSC architectures, including C-PSCs and planar p-i-n devices.

## Abstract

The most typical
hysteresis in the current density–voltage
(J–V) curve of perovskite
solar cells (PSCs) shows better performance in the backward (BW) than
in the forward (FW) voltage scan (normal hysteresis). The opposite,
where the FW scan yields higher photocurrent, is known as inverted
hysteresis and is also frequently observed. Here, we examine PSCs
exhibiting both normal and inverted hysteresis, depending on scan
rate and preconditioning. Spectral changes in the external quantum
efficiency (EQE) linked to ionic redistribution reveal that inverted
hysteresis arises from blue-range photocurrent losses caused by enhanced
recombination at the interfaces due to ionic accumulation. This trend
is consistent across PSC architectures, as demonstrated for triple
mesoscopic carbon-based (C-PSCs) and planar p-i-n devices. Combined
with drift-diffusion simulations, the results show that ionic losses
can be bidirectional, and the hysteresis direction depends on how
the ionic distribution impacts charge collection efficiency.