Avoiding buried voids
The buried interfaces of perovskite solar cells are difficult to alter after synthesis. During manufacture, Chen et al. removed perovskite films with dimethyl sulfoxide solvent from the hole-transfer layer and observed a substantial void fraction that degraded film performance. Replacing most of the dimethyl sulfoxide with carbohydrazide, a lead-coordinating compound with a much higher boiling point, eliminated voids. Such solar cells maintained high power conversion efficiency after 550 hours of operation at 60°C.
Science, abi6323, this issue p. 902
The interfaces of perovskite solar cells (PSCs) are important in determining their efficiency and stability, but the morphology and stability of imbedded perovskite-substrate interfaces have received less attention than have top interfaces. We found that dimethyl sulfoxide (DMSO), which is a liquid additive broadly applied to enhance perovskite film morphology, was trapped during film formation and led to voids at perovskite-substrate interfaces that accelerated the film degradation under illumination. Partial replacement of DMSO with solid-state carbohydrazide reduces interfacial voids. A maximum stabilized power conversion efficiency (PCE) of 23.6% was realized for blade-coated p-type/intrinsic/n-type (p-i-n) structure PSCs with no efficiency loss after 550-hour operational stability tests at 60°C. The perovskite mini-modules showed certified PCEs of 19.3 and 19.2%, with aperture areas of 18.1 and 50.0 square centimeters, respectively.