Chen Weijie

Lead halide perovskite (PVSK)-based solar cells with certified power conversion efficiencies (PCEs) as high as 23.3% have demonstrated the potential to be competitive compared with emerging thin-film solar cells such as CIGS (copper-indium-gallium-selenide, 22.6%) and CdTe (22.1%) and have outperformed multicrystalline Si photovoltaic (PV) technology (22.3%). One of the major obstacles for moving PVSK PV technology forward to the commercial market is the poor operational stability of the device. In this review, to evaluate the progress and whether perovskite solar cells show promise for attaining long-term stability, we extract the T₈₀ parameter (time lapsed for a solar cell to decay 20% from its initial PCE) from the operational stability profiles reported in the literature. While a steady increase in PCE is observed based on our analysis, T₈₀ does not show significant improvement. Instead, a stagnant trend is found with a T₈₀ value around 6,000 hr. This finding clearly reveals that lifetime is still one of the pressing challenges, and more concentrated research efforts are needed to increase the stability of PVSK solar cells. In terms of research strategies, fundamental understanding of the degradation processes may hold the key to achieving breakthroughs in this regard and ultimately long-term outdoor applications. The structure of a PVSK solar cell is complex, comprising several functional layers stacked together. In addition to PVSK degradation mechanisms under operation conditions (e.g., photo-, thermal-, strain-, mechanical-induced instabilities, environment, etc.), each of the functional layers and their interactions with PVSK need to be optimized to further improve the lifetime of the overall solar cell device. Descriptions of the above-mentioned degradation phenomena, updated discussions on strategies to improve stability, protocols for long-term stability measurements, and analysis methods of solar cell performance versus time profiles constitute the main focus of this review.

With the rapid developments in lead halide perovskite solar cell technology, record-high power conversion efficiencies have been achieved, and significant research efforts have been directed toward stability, which is still a major challenge facing the commercialization of perovskite solar cell technology. In this review article, we review the research progress that has been made on the stability of perovskite solar cells. We start with an analysis of recently reported operational stability profiles of perovskite solar cells. On the basis of the analysis, we determine the solar cell lifetime (i.e., T₈₀ values) and the total amount of energy generated during the lifespan of a perovskite solar cell, from which several trends are inferred. In the subsequent sections, we further examine the instability issues associated with various constituents in a perovskite solar cell and the new methods/strategies that have been developed to solve these issues.