Temperature-dependent Hysteresis in MAPbI3 Solar Cells

TL;DR

This study investigates how temperature influences hysteresis in MAPbI3 perovskite solar cells, revealing different ion migration behaviors and activation energies in regular and inverted architectures, which affect device performance.

Contribution

It provides a systematic analysis of temperature-dependent hysteresis, highlighting the distinct ion migration mechanisms and activation energies in different cell architectures.

Findings

Inverted cells have higher ion migration rates than regular cells.

Hysteresis regimes differ between regular and inverted cells due to interface effects.

Main recombination mechanism is trap-assisted Shockley-Read Hall in the space charge region.

Abstract

Hysteresis in the current-voltage characteristics of hybrid organic-inorganic perovskite-based solar cells is one of the fundamental aspects of these cells that we do not understand well. One possible cause, suggested for the hysteresis, is polarization of the perovskite layer under applied voltage and illumination bias, due to ion migration within the perovskite. To study this problem systemically current-voltage characteristics of both regular (light incident through the electron conducting contact) and so-called inverted (light incident through the hole conducting contact) perovskite cells were studied at different temperatures and scan rates. We explain our results by assuming that the effects of scan rate and temperature on hysteresis are strongly correlated to ion migration within the device, with the rate-determining step being ion migration at/across the interfaces of the perovskite layer with the contact materials. By correlating between the scan rate with the measurement temperature we show that the inverted and regular cells operate in different hysteresis regimes, with different activation energies of 0.28+-0.04 eV and 0.59+-0.09 eV, respectively. We suggest that the differences, observed between the two architectures are due to different rates of ion migration close to the interfaces, and conclude that the diffusion coefficient of migrating ions in the inverted cells is 3 orders of magnitude higher than in the regular cells, leading to different accumulation rates of ions near the interfaces. Analysis of VOC as a function of temperature shows that the main recombination mechanism is trap-assisted (Shockley-Read Hall, SRH) in the space charge region, similar to what is the case for other thin film inorganic solar cells.