Core/shell nanowire heterostructures as efficient nanoscale photon upconverters

Photon energy upconversion in semiconductor nanowires (NWs) could be utilized in a verity of nano- optoelectronic and photonic applications. In this work we show that efficiency of energy upconversion due to two-photon absorption (TPA) can be boosted in NW heterostructures engineered so that (i) an intermediate TPA step involves band states of the narrow bandgap region; (ii) at least one of the carriers created after the first photon absorption can freely diffuse to the wider bandgap region; and (iii) carriers generated after the intermediate step have a long lifetime. These conditions are shown to be satisfied in radial GaNAs(P)/GaAs(P) NW heterostructures leading to up to 500 times increase in the upconversion efficiency relative to that of the constituent materials. The upconversion efficiency is found to be independent of the excitation power and can be further enhanced (up to 15%) in hybrid NW-on-gold structures, engineered to maximize light absorption within the shell region under the upconversion conditions. This work, therefore, demonstrates the great potential of dilute nitride NWs as energy upconverters and provides general guidelines for designing efficient nanoscale photon upconverters based on NW heterostructures.

[1] M. Jansson et al. ACS Nano 16, 12666 (2022)