Dynamics of Photoinduced Degradation of Perovskite Photovoltaics: From Reversible to Irreversible Processes

Abstract

The operational stability of perovskite solar cells (PSCs) remains a limiting factor in their commercial implementation. We studied the long-term outdoor stability of ITO/SnO2/Cs0.05((CH3NH3)0.15(CH­(NH2)2)0.85)0.95PbI2.55Br0.45/spiro-OMeTAD/Au cells, as well as the dynamics of their degradation, under simulated sunlight indoors and their recovery in the dark. The extent of overall degradation was found to depend on processes occurring both under illumination and in the dark, i.e., during the daytime and nighttime, with the dynamics varying with cell aging. Full recovery of efficiency in the dark was observed for cells at early degradation stages. Further cell degradation resulted in recovery times much longer than one night, appearing as irreversible degradation under real operational conditions. At later degradation stages, very different dynamics were observed: short-circuit current density and fill factor exhibited a pronounced drop upon light turn-off but strong improvement under subsequent illumination. The interplay of reversible and irreversible degradation processes with different recovery dynamics was demonstrated to result in changes in the cell’s diurnal PCE dependence during its operational lifespan under real sunlight conditions.

Outdoor performance monitoring of perovskite solar cell mini-modules: Diurnal performance, observance of reversible degradation and variation with climatic performance

“…A second reason could be related to the low FF observed with the MAPI modules (the maximum measured is 34% during this day). As demonstrated by Katz et al for the cells with high value of series resistance (Rs), a sub-linear relationship between JSC and irradiance can be explained by a monotonic increase in the cell's series resistance losses with increase irradiance [22]. This is known to result initially in a decrease of the FF, which is also consistent with our findings in figure 2(d).…”

Consensus statement for stability assessment and reporting for perovskite photovoltaics based on ISOS procedures

“…Various PSC degradation modes have repeatedly been shown to be entirely or partly reversible in the dark (often referred to as metastability) 20,36,51,58,74,[80][81][82][83] . Therefore, cycling through light-dark periods to simulate day-night cycles constitutes a significantly different stress test than applying constant illumination (ISOS-L) 4,74 .…”

Machine Learning for Perovskites' Reap-Rest-Recovery Cycle

“…When properly rested, all figures-of-merit of the device can be restored to >70% of their initial values (see Figure 2C for a recovery example). 18 This work shows that the required duration of the rest phase depends on how much performance is lost during the actual solar cell operation. For an HOIP device that decays to 80% (aged to its T 80 lifetime) of its initial PCE (in blue in the left graph), only 3 hr of rest returns all figures-of-merit to >90% of their starting values.…”

“…Contrastingly, the same device at 50% of initial power output (see right graph, corresponding to T 50 ) needs more than 30 hr to recover to $80%. 18 Researchers have also identified HOIP cells with contrary fatigue behavior that recover their performance while under illumination, instead of under dark contitions. 19 Moreover, the restoration behavior can strongly depend on the environmental conditions during aging, where both dark-recovery and light-recovery can occur.…”

“…In this example, greater than 70%, regardless of whether the device was used through its T 80 or T 50 lifetime. Adapted with permission from Khenkin et al,18 Copyright 2018 American Chemical Society.…”