Bifunctional conjugated chemical bonds for trap inactivation and ion immobilization in fully ambient-air processed perovskite solar cells

For the past few years, air-processed perovskite solar cells (PSCs) have raised interests from researchers around the world, due to the urgent demand for the roll-to-roll (R2R) industrialization. However, lots of detrimental effects, such as imperfect active film quality and plentiful traps on the surface, or especially grain boundaries (GBs) for the samples fabricated under the ambient conditions, can seriously damage both the performance and stability of PSCs. Thereby, in this study, a cross-linking passivator, dodecanoic acid (DA), was incorporated in order to improve the crystallinity of air-processed perovskite films. On the one hand, DA agents with carboxy group and –O points, could chelate tightly with nonbonding Pb2+ ions of perovskite crystal through donor-π-acceptor (D-π-A) conjugation, as well as interact with I− anions through hydrogen network. The hindered trap formation and immobilized ions improve the power conversion efficiency (PCE) of the device. On the other hand, the long hydrophobic alkyl chains of DA were prone to be accumulated at the GBs of the perovskite grains, thus boosting the moist resistance. Consequently, the champion device gained a PCE of 20.23% with hindered hysteresis. Moreover, the unpackaged DA-passivated PSC retains 81.7% of its original PCE after aging under ambient conditions for 5 weeks. This simple and viable approach for fabricating perovskite-based optoelectronic device with high performance and promising stability, can promote its large production and commercialization.