Solar cells face a significant challenge when individual cells within a module are shaded, leading to reverse bias conditions. This situation can result in increased temperature and potential damage to the cells, making them unstable and decreasing their overall performance over time. The University of North Carolina at Chapel Hill researchers have recently presented a new strategy to enhance the stability of perovskite solar cells (PSCs) under reverse bias conditions. This strategy could pave the way for the wide-scale deployment of perovskite-based photovoltaics in real-world settings.
Perovskite cells are known for having a much thinner photoactive layer compared to other existing photovoltaic cells, making them more susceptible to the effects of reverse bias conditions. Additionally, the ion migration in perovskites further decreases their stability under reverse bias, resulting in breakdown or degradation in just seconds to minutes under a few volts of reverse bias. If left unresolved, this issue could force perovskite module manufacturers to incorporate numerous bypass diodes to safeguard the cells, leading to increased fabrication costs.
The research team, led by Jinsong Huang, delved into previous literature to discover that certain PSCs exhibited greater stability under reverse bias conditions. This discovery motivated them to explore the underlying mechanisms responsible for this improved stability in order to find a viable solution. By studying p-i-n structured PSCs and utilizing an optimized perovskite composition to eliminate potential degradation pathways, the team hoped to identify a method to enhance perovskite cell stability.
Experimenting with various reverse bias values and device stacks, Huang and his team closely monitored the behavior of the PSCs to determine the degradation mechanisms at play. Through their investigations, they distinguished between breakdown and gradual degradation, with the former occurring under high reverse bias in a short timeframe and the latter under low reverse bias over a longer duration. This distinction allowed the researchers to pinpoint the electrochemical reactions triggering the corrosion of the Cu electrode, ultimately leading to the breakdown of the solar cells.
The team’s experiments revealed a series of electrochemical reactions associated with the degradation of PSCs under reverse bias conditions, specifically the generation of iodine causing Cu electrode corrosion. To combat this issue, the researchers implemented a device stacking of lithium fluoride/tin oxide/indium tin oxide to inhibit iodine formation and electrode corrosion under reverse bias. This modification extended the lifetime of the PSCs up to 1,000 hours under a reverse bias of -1.6 V, showcasing a remarkable level of stability that surprised the researchers.
The insights gained through this research could significantly impact the development of more stable perovskite-based PVs, potentially accelerating their large-scale commercialization. As the research project concludes, Huang and his team are eager to pursue additional studies to establish the upper limit of reverse bias stability for PSCs. Through ongoing research and innovation, the future of perovskite solar cells looks promising, with increased stability paving the way for widespread use in the renewable energy sector.
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