Inorganic Cu2ZnSnS4 hole transport layer for perovskite light-emitting diodes

Inorganic Cu2ZnSnS4 (CZTS) has garnered significant attention in the field of solar cells owing to its high hole mobility, suitable optical bandgap, cost-effective and earth-abundant elemental constituents. In particular, the deeper highest occupied molecular orbital (HOMO) of CZTS makes it an alternative for the traditional organic hole transport layer (HTL) material poly(3,4-ethyllenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), which can suppress acidic interface and hygroscopic problem in perovskite light-emitting diodes (PeLEDs). Herein, we demonstrate CZTS as a novel inorganic HTL for green FAPbBr3 PeLEDs, achieving a peak external quantum efficiency (EQE) of 7.59% and a maximum luminance of 27 000 cd m−2 (emitting at 529 nm). The fluorescence properties of the perovskite films and interfacial behaviors of CZTS/FAPbBr3 were investigated through surface state regulation of CZTS HTL. High hole mobility (0–30 cm2 V−1 s−1) of CZTS HTL and low hole injection barrier (∼0.13 eV) between CZTS and perovskite endow the CZTS-based PeLEDs with enhanced hole transport capability and suppressed interfacial carrier accumulation. In addition, an attractive cost-effectiveness advantage of about $0.24 per g synthesizing CZTS makes it a promising competitor to mainstream organic HTL materials such as PEDOT:PSS (∼$1.3 per g). An in-depth understanding of this novel CZTS HTL makes an essential step forward for the commercialization of PeLEDs.