Carrier-Funneling-Induced Efficient Energy Transfer in CdS_xSe_1–x Heterostructure Microplates

The energy transfer of semiconductor heterostructure microplates (H-MPs) plays a crucial role in the performance of various optoelectronic devices they construct. Compared to compact heterostructures, the energy transfer in H-MPs involves an additional carrier diffusion process which results in a low carrier population at the heterointerface and thereby leads to a poor energy-transfer efficiency. Based on an energy-funneling mechanism, CdSxSe1–x lateral H-MPs with a bandgap-graded donor are engineered to efficiently and directionally drive carriers to the heterointerface. The cathode-luminescence study visually presents the enhancement of the carrier transport efficiency. We systematically studied the energy-transfer process in the H-MPs through time-resolved photoluminescence experiments. Compared to the low-energy input efficiency (EIE) of ∼20.5% in a common H-MP without a bandgap-graded donor, the EIE for a CdSxSe1–x H-MP with a bandgap-graded donor can be improved to ∼109.3%. This bandgap engineering gives a general strategy to improve the energy-transfer efficiency in H-MPs.