Light-activated photocurrent degradation and self-healing in perovskite solar cells

Abstract

Solution-processed organometallic perovskite solar cells have emerged as one of the most promising thin-film photovoltaic technology. However, a key challenge is their lack of stability over prolonged solar irradiation. Few studies have investigated the effect of light soaking on hybrid perovskites and have attributed the degradation in the optoelectronic properties to photochemical or field-assisted ion migration. Here we show that the slow photocurrent degradation in thin-film photovoltaic devices is due to the formation of light-activated meta-stable deep-level trap states. However, the devices can self-heal completely by resting them in the dark for <1 min or the degradation can be completely prevented by operating the devices at 0 °C. We investigate several physical mechanisms to explain the microscopic origin for the formation of these trap states, among which the creation of small polaronic states involving localized cooperative lattice strain and molecular orientations emerges as a credible microscopic mechanism requiring further detailed studies.

Migration of cations induces reversible performance losses over day/night cycling in perovskite solar cells

“…prolonged exposure to continuous light and voltage bias. 29,39,[50][51][52][53][54][55] In this work, we provide direct evidence of electric field-induced ion migration and its effects on the long-term performance of perovskite solar cells working under different loads.…”

Methodologies toward Efficient and Stable Cesium Lead Halide Perovskite‐Based Solar Cells

“…The stability of the solar cells was examined under continuous 1 sun illumination, showing that the CsPbI 2 Br‐based solar cell retained its initial PCE for 1500 h, while the MAPbI 3 ‐based solar cell severely degraded within 50 h (Figure 13b, bottom). It was somewhat encouraging that CLH perovskites could be a potential alternative to organic perovskites as photostable solar cell materials 81, 82. The soft nature of organic molecules and dipole‐induced reorientation might be responsible for this behavior, which is supported by the preceding literature 66.…”

Self‐Healing Materials for Next‐Generation Energy Harvesting and Storage Devices

“…[111][112][113][114] Nie et al demonstrated that the degradation of the hybrid perovskite solar cell performance under constant solar illumination was due to the degradation of the photocurrent, which could achieve a rapid self-healing (<1 min) in the dark to its original value. [115] The PCE of the hybrid perovskite solar cell device degraded after 2 h of constant solar illumination, could also recover to its original values after resting the device in the dark (Figure 3a). Based on the detailed experimental and theoretical analysis, the photocurrent degradation should be ascribed to the increasing number of light-activated metastable trap states that could accumulate during long-term light soaking, which leads to the formation of charged regions in the bulk of the thin film.…”

“…Reproduced with permission. [115] Copyright 2016, Nature Publishing Group. ) and after self-healing (c).…”