Degradation of Perovskite Thin Films and Solar Cells with Candle Soot C/Ag Electrode Exposed in a Control Ambient

Perovskite solar cells (PSCs) have already achieved efficiencies of over 25%; however, their instability and degradation in the operational environment have prevented them from becoming commercially viable. Understanding the degradation mechanism, as well as improving the fabrication technique for achieving high-quality perovskite films, is crucial to overcoming these shortcomings. In this study, we investigated details in the changes of physical properties associated with the degradation and/or decomposition of perovskite films and solar cells using XRD, FESEM, EDX, UV-Vis, Hall-effect, and current-voltage (I-V) measurement techniques. The dissociation, as well as the intensity of perovskite peaks, have been observed as an impact of film degradation by humidity. The decomposition rate of perovskite film has been estimated from the structural and optical changes. The performance degradation of novel planner structure PSCs has been investigated in detail. The PSCs were fabricated in-room ambient using candle soot carbon and screen-printed Ag electrode. It was found that until the perovskite film decomposed by 30%, the film properties and cell efficiency remained stable.

Perovskite CH3NH3PbI3–XClx Solar Cells. Experimental Study of Initial Degradation Kinetics and Fill Factor Spectral Dependence

The main drawback of the methylammonium lead halide perovskite solar cells is their degradation in ambient atmosphere. To investigate ambient-air-induced cell degradation, spectral dependencies of open-circuit voltage (VOC), fill factor (FF) and the power conversion efficiency (PCE) have been acquired (for the first time reported in literature).Our custom-made measurement system allowed us to perform measurements of the abovementioned entities in situ directly in vacuum during and after thermal deposition of the electrode. We also studied how these parameters in vacuum changed after cell exposure to ambient air for 85 min (50 nm top electrode) and for 180 min (100 nm top Ag electrode). For fresh CH3NH3PbI3–xClx cell (never been in open air) with very high shunt resistance of 3·107 Ω·cm2 (with practically no shorts and therefore FF could be determined mainly by charge carrier recombination processes) we found that FF in vacuum increased along with an increase of the incident photon energy from 0.55 at 760 nm up to 0.82 at 400 nm. Hypothesis considering hot polaron participation in charge carrier photogeneration and recombination processes as well as another competing hypothesis were offered as possible explanations for the observed FF increase.The kinetics of short-circuit photocurrent EQE with a change in pressure was also investigated. It was also shown that perovskite solar cell degradation could be noticeably reduced by increasing the top Ag electrode thickness to at least 100 nm, which could possibly facilitate the usual encapsulation process.