Peng Huang

Three-dimensional halide-based perovskites have emerged as promising semiconducting light harvesters for thin-film solar cell fabrication; however, their intrinsic instability under humidity restricts their potential commercialization. To address such challenges, the development of low-dimensional/layered Dion–Jacobson (DJ) phase perovskites has recently gained substantial attention due to their intriguing environmental stability and competitive power conversion efficiency. In this Review, we have screened and focused our investigation on the DJ phase in layered perovskites for solar cell fabrication, especially elucidation of the active role played by organic spacer cations. We also discuss the possible strategies that can be employed to further push the performance of DJ-based perovskite solar cells.

Abstract Three-dimensional bimetallic nanoframes with high spatial diffusivity and surface heterogeneity possess remarkable catalytic activities owing to their highly exposed active surfaces and tunable electronic structure. Here we report a general one-pot strategy to prepare ultrathin octahedral Au 3 Ag nanoframes, with the formation mechanism explicitly elucidated through well-monitored temporal nanostructure evolution. Rich crystalline defects lead to lowered atomic coordination and varied electronic states of the metal atoms as evidenced by extensive structural characterizations. When used for electrocatalytic methanol oxidation, the Au 3 Ag nanoframes demonstrate superior performance with a high specific activity of 3.38 mA cm −2 , 3.9 times that of the commercial Pt/C. More intriguingly, the kinetics of methanol oxidation on the Au 3 Ag nanoframes is counter-intuitively promoted by carbon monoxide. The enhancement is ascribed to the altered reaction pathway and enhanced OH − co-adsorption on the defect-rich surfaces, which can be well understood from the d-band model and comprehensive density functional theory simulations.

As a hole-transport layer (HTL) material, poly(3,4-ethylenedioxythiophene):polystyrene-sulfonate (PEDOT:PSS) was often criticized for its intrinsic acidity and hygroscopic effect that would in the long run affect the stability of perovskite solar cells (Pero-SCs). As alternatives, herein water-soluble two-dimensional (2D) transition metal dichalcogenides (TMDs), such as MoS2 and WS2 were used as HTLs in p–i–n Pero-SCs. It was found that the content of 1T phase in 2D TMDs HTLs is centrally important to the power conversion efficiencies (PCEs) of Pero-SCs, and the 1T-rich TMDs (as achieved from exfoliation and without postheating) lead to much higher PCEs. More importantly, as PEDOT:PSS was replaced by 2D TMDs, both the PCEs and stability of Pero-SCs were significantly improved. The highest PCEs of 14.35 and 15.00% were obtained for the Pero-SCs with MoS2 and WS2, respectively, whereas the Pero-SCs with PEDOT:PSS showed a highest PCE of only 12.44%. These are up to date the highest PCEs using 2D TMDs as HTLs. After being stored in a glovebox for 56 days, PCEs of the Pero-SCs using MoS2 and WS2 HTLs remained 78 and 72%, respectively, whereas the PCEs of Pero-SCs with PEDOT:PSS almost dropped to 0 over 35 days. This study demonstrates that water-soluble 2D TMDs have great potential for application as new generation of HTLs aiming at high performance and long-term stable Pero-SCs.

Thick, wide-bandgap materials as photoactive layers in semi-transparent Pero-SCs realized >20% AVT and ∼10% PCE.