Electronic Structure Modulation of 2D Colloidal CdSe Nanoplatelets by Au25 Clusters for High-Performance Photodetectors

The electronic interactions between colloidal two-dimensional (2D) semiconductor nanoplatelets (NPLs) and Au nanoclusters (NCs) remain unexplored, which are decisive for optoelectronic applications. Here, we report the synthesis of heterostructures based on colloidal 2D CdSe NPLs and Au-25 NCs and investigate their electronic interactions using density functional theory (DFT) calculations. The steady state, time-resolved photoluminescence, and transient absorption (TA) spectroscopic studies are carried out to understand the charge-transfer dynamics. The replacement of CdSe bands by Au bands in the valence band edge in CdSe NPLs-Au NCs heterostructures attests the charge transfer from the conduction band of CdSe to Au. Ultrafast TA spectroscopy further confirms the electron transfer in the heterostructures, and the faster bleach recovery kinetics is also observed in CdSe NPLs-Au NCs heterostructures. The observed charge transfer from the conduction band of CdSe NPLs to Au NCs has been corroborated by the difference in the orbital composition of the valence band edges between CdSe and Au NCs, as calculated by DFT. Photodetectors fabricated with these heterostructures feature high enhancement in photocurrent (similar to 350-fold), fast photoresponse (similar to 200 ms), and high detectivity (similar to 2.5 x 10(11) Jones), which hold promise for the future design of 2D NPL-based materials for optoelectronic applications.