Large-area perovskite solar cells employing spiro-Naph hole transport material

Stabilizing the best-performing state-of-the-art perovskite solar cells (PSCs) based on a spiro-OMeTAD hole transport material (HTM), without sacrificing their high power conversion efficiency (PCE) levels, is a challenging task. By exploiting the symmetry-tuned strategy at the molecular level, we have developed spiro-OMeTAD analogues (namely, the spiro-Naph series) with asymmetric phenylnaphthylamine edge units. The new spiro-Naph HTM-based PSC achieved a high PCE of 24.43%, higher than that achieved with spiro-OMeTAD. In addition to excellent stability when soaking the encapsulated device with continuous light, superior device stability was also obtained for the unencapsulated spiro-Naph-based PSC—a PCE of 21.12% was retained in air with ~25% relative humidity after 2,000 h and a PCE of 18.79% was retained at an elevated temperature of 60 °C after 400 h. We also constructed a spiro-Naph-based large-area module (25 cm2) with a PCE of 21.83%.