Eliminating Charge Accumulation via Interfacial Dipole for Efficient and Stable Perovskite Solar Cells.

Elimination of interfacial charge trapping is still a challenge for promoting both efficiency and operational stability of organic-inorganic perovskite solar cells (PSCs). Herein, an effective interface dipole, trimethylamine oxide (TMAO) regarded as a connecting bridge, is inserted between the electron transport layer (ETL) and the perovskite layer to suppress charge accumulation and fabricate highly efficient and stable PSCs. As demonstrated by energy level alignment and morphology characterization, TMAO dipoles could achieve a decreased energetic barrier of electron transport and substantial padding of perovskite in the mesoporous ETL. Thus, they facilitate the charge transfer and reduce trapped charge densities as well as recombination centers at the interface between perovskite and ETL. These desirable properties improve the device efficiency to 21.77% and weaken the hysteresis index almost to 0. More importantly, the stability of the unencapsulated PSCs is remarkably enhanced. The findings provide valuable insights into the role of a dipolar molecule in boosting the performance of PSC devices.