Sanjun Yang, Kailang Liu, Wei Han, Liang Li, Fakun Wang, Xing Zhou, Huiqiao Li*, Tianyou Zhai*, Salt-assisted Growth of P-type Cu9S5 Nanoflakes for P-N Heterojunction Photodetectors with High Responsivity, Advanced Functional Materials 2020, 30, 1908382.
https://doi.org/10.1002/adfm.201908382.
Abstract: P-n junctions based on two-dimensional (2D) van der Waals (vdW) heterostructure are one of the most promising alternatives in the next-generation electronics and optoelectronics. By choosing different 2D transition metal dichalcogenides (TMDCs), the p-n junctions have tailored energy band alignments and exhibit superior performance as photodetectors. The p-n diodes working at reverse bias commonly have high detectivity due to suppressed dark current but suffer from low responsivity resulting from small quantum efficiency. Greater build-in electric field in the depletion layer can improve the quantum efficiency by reducing recombination of charge carriers. Herein, Cu9S5, a novel p-type semiconductor with direct bandgap and high optical absorption coefficient, is synthesized by salt-assisted chemical vapor deposition (CVD) method. The high density of holes in Cu9S5 endows the constructed p-n junction, Cu9S5/MoS2, with strong build-in electric field according to Anderson heterojunction model. Consequently, the Cu9S5/MoS2 p-n heterojunction has low dark current at reverse bias and high photoresponse under illumination due to the efficient charge separation. The Cu9S5/MoS2 photodetector exhibits good photodetectivity of 1.6 ´ 1012 Jones and photoresponsivity of 76 A W-1 under illumination. This study demonstrates Cu9S5 is a promising p-type semiconductor for high performance p-n heterojunction diodes.
