Improving Efficiency and Stability of Perovskite Solar Cells Enabled by A Near-Infrared-Absorbing Moisture Barrier

Simultaneously improving device efficiency and stability is the most important issue in perovskite solar cell (PSC) research. Here, we strategically introduce a multi-functional interface layer (MFIL) with integrated roles of: (1) electron transport, (2) moisture barrier, (3) near-infrared photocurrent enhancement, (4) trap passivation, and (5) ion migration suppression to enhance the device performance. The narrow-band-gap non-fullerene acceptor, Y6, was screened out to replace the most commonly used PCBM in the inverted PSCs. A significantly improved power conversion efficiency of 21.0% was achieved, along with a remarkable stability (up to 1,700 h) without encapsulation under various external stimuli (light, heat, and moisture). Furthermore, systematic studies of the molecular orientation or passivation and the charge carrier dynamics at the interface between perovskite and MFIL were presented. These results offer deep insights for designing advanced interlayers and establish the correlations between molecular orientation, interface molecular bonding, trap state density, non-radiation recombination, and the device performance. [Display omitted] •A new strategy to enhance the device performance while simplifying the device structure•New design rules to rationally screen multi-functional interface layer•Long-term stability without encapsulation upon exposure to moisture, heat, and light•Correlations between molecular orientation or passivation and device performance Perovskite solar cells (PSCs) have attracted tremendous attention because of the high efficiencies, ease of fabrication, and low cost of production. However, further enhancement of device efficiency has been a bottleneck, and the instability of the PSCs hampers their commercialization. In this work, we strategically introduce a new multi-functional interface layer that integrates five different functions to improve the device efficiency and long-term stability of PSCs, pushing forward the development of the PSC technology. A significantly improved power conversion efficiency of 21.0% was achieved along with the remarkable stability (up to 1,700 h) without encapsulation under various external stimuli (light, heat, and moisture). These results open new avenues to design advanced interlayers, simplifying the device structure, and enhancing efficiency and stability, that can accelerate the market readiness of perovskite-based optoelectronics. A multi-functional interface layer with integrated role