Perovskite and silicon tandem cells capture more of the solar spectrum than silicon alone and have climbed rapidly in efficiency, but their thermal durability has lagged badly behind the twenty to twenty-five year warranties that silicon panels routinely carry. Researchers at NUS traced the problem to an unexpected place. The main source of heat-driven degradation was not the perovskite layer itself but a thin self-assembled monolayer that transfers charge between layers.
Under heat that monolayer lost its orderly structure, disrupting current flow through the device. The team redesigned it to form chemical links that lock the layer into a sturdier network, so that thermal energy no longer disorders the molecular arrangement. The diagnosis is as significant as the fix, since considerable effort across the field has focused on stabilising perovskite composition rather than the interfacial layers around it.
The resulting devices performed well on both axes. Efficiencies exceeded 34 per cent, including a certified 33.6 per cent, and the cells retained over 96 per cent of initial performance after 1,200 hours of continuous illumination at 65 degrees Celsius. The study was led from the Department of Chemistry in the NUS Faculty of Science with the Department of Materials Science and Engineering, and was published in Science.
Laboratory stability under controlled illumination is not the same as two decades on a roof, and the team plans prototype testing under tropical conditions in Singapore along with scale-up to module dimensions. Humid equatorial climates impose stresses that temperate-climate testing does not reproduce, making Singapore an unusually demanding and therefore useful proving ground for tandem photovoltaics.