Enhanced moisture-resistant and highly efficient perovskite solar cells via surface treatment with long-chain alkylammonium iodide

Defects distributed between the perovskite film and the hole transport layer (HTL) are easily generated, which can not only act as charge recombination sites, but also provoke the irreversible decomposition of the perovskite structure as well as severe degradation of devices. Herein, aiming to eliminate the interfacial defects and improve the moisture-resistant of perovskite films, we introduced a long-chain alkylammonium salt, dodecylammonium iodide (DDAI). DDAI with high moisture tolerance can play the role of an efficient passivation layer between the perovskite absorber layer and HTL, ameliorating the interfacial carrier recombination and energy band structure. The analytical results have shown that the introduced -NH3+ and I− from DDAI can effectively passivate the surface defects of perovskite and enhance the surface resistance to moisture. Benefiting from the suppressed non-radiative recombination and better-matched energy levels brought by the introduction of DDAI, the optimal photoelectric conversion efficiency of 21.85% for DDAI-modified devices can be achieved, superior to the pristine (19.03%). Moreover, the passivated devices without encapsulation exhibited excellent long-term durability due to the inherent hydrophobic features of the long-chain organic ammonium, which sustained 90.4% of their original efficiency for 30 days under an air environment (relative humidity ≈ 20 ± 5%). Our work offers an avenue for improving the photoelectric performance and water resistance of perovskite solar cells.