New Solar Cells Withstand Shading, Maintain High Efficiency

Thin-film solar technologies, while offering advantages like flexibility and cost-effectiveness, often suffer from reduced efficiency and potential damage when partially shaded. This shading can create a negative voltage, known as reverse-bias stress, which hinders power generation. A team at The Hong Kong Polytechnic University (PolyU) has engineered a new generation of perovskite-organic tandem solar cells (POTSCs) designed to overcome this limitation.

These newly developed POTSCs demonstrate remarkable resilience. Even when subjected to a significant reverse bias of -40 V, the tandem devices were able to retain more than 90% of their initial power-generation efficiency. This level of performance under such stress far exceeds that of current thin-film solar technologies, marking a significant advancement toward their practical implementation.

The key to this improved durability lies in the team's approach to addressing defects within the solar cells. By suppressing specific clusters within the power-generating active layer, they minimized defects that can immobilize charges and cause efficiency loss or damage. This innovation resulted in organic solar cells with an irreversible breakdown voltage exceeding -35 V.

Furthermore, the research focused on preventing reverse tunneling in the tandem cells, which protects the perovskite layer. The study also highlights the long-term stability of these POTSCs, with devices retaining 90% efficiency after 12 hours at -20 V and an impressive 97% efficiency after 2,000 hours at -4.5 V. These findings were published in the journal Nature Materials.