Plasmon-enhanced perovskite solar cells using ultra-thin LiF spacer isolating AgAl and Au composite nanoparticles from metal electrode

Abstract Plasmon enhanced perovskite solar cells (PSCs) incorporated with AgAl and Au composite nanoparticles (NPs) isolating from AgAl metal electrode with ultra-thin LiF spacer were investigated. PSCs with AgAl-Au composite NPs got 17.02% of the power conversion efficiency (PCE), which is 11.10% higher than PCE (15.32%) of the control PSC with only AgAl electrode. Furthermore, the hysteresis effect of PSCs with LiF modified AgAl and Au composite NPs can be neglected compared to the control cells without NPs and LiF spacer. In the meanwhile, carrier transport and collection probabilities of PSCs with AgAl and Au composite NPs were increased to 96.86% from 89.51% in control cells, indicating the improved electron transport and extraction ability. The enhanced PCEs of PSCs with AgAl(3 nm)/Au(2 nm)/LiF(1 nm) are attributed to the improved light absorption of perovskite layer and the reduced contact barrier at metal electrode, which can be supported with its enhanced photon-to-electron conversion efficiency (△IPCE) and the disappeared negative capacitive behavior. Furthermore, the obviously reduced work function values of AgAl-Au composite NPs and AgAl metal electrode after LiF modification were observed with ultraviolet photoelectron spectroscopy spectra. Our results indicate that thermally evaporating a ultra-thin LiF spacer can well inhibit the energy dissipation of plasmon effects of AgAl-Au composite NPs and reduce the contact barrier between PCBM and AgAl metal electrode, which is an efficient strategy to achieve efficient plasmon-enhanced perovskite solar cells.