A route to phase controllable Cu2ZnSn(S(1-x)Se(x))4 nanocrystals with tunable energy bands.

Cu2ZnSn(S(1-x)Se(x))4 nanocrystals are an emerging family of functional materials with huge potential of industrial applications, however, it is an extremely challenging task to synthesize Cu2ZnSn(S(1-x)Se(x))4 nanocrystals with both tunable energy band and phase purity. Here we show that a green and economic route could be designed for the synthesis of Cu2ZnSn(S(1-x)Se(x))4 nanocrystals with bandgap tunable in the range of 1.5-1.12 eV. Consequently, conduction band edge shifted from -3.9 eV to -4.61 eV (relative to vacuum energy) is realized. The phase purity of Cu2ZnSn(S(1-x)Se(x))4 nanocrystals is substantiated with in-depth combined optical and structural characterizations. Electrocatalytic and thermoelectric performances of Cu2ZnSn(S(1-x)Se(x))4 nanocrystals verify their superior activity to replace noble metal Pt and materials containing heavy metals. This green and economic route will promote large-scale application of Cu2ZnSn(S(1-x)Se(x))4 nanocrystals as solar cell materials, electrocatalysts, and thermoelectric materials.