Boosting Upconversion through Selective Interfacial Energy Transfer toward Infrared Sub-bandgap Photodetection

Photon upconversion in nanocrystals shows significant promise in versatile frontier applications; however, it has remained a huge challenge to overcome the long-standing concentration quenching effect. Here we report a conceptual model to boost upconversion through selective control of interfacial energy transfer (IET) in core-shell-based nanocrystals. Such a design enables both activator and sensitizer to achieve 100% doping in a single nanocrystal in contrast to conventional nanoparticles. Importantly, it is able to greatly minimize the nonradiative energy loss by the atomic-level spatial manipulation of interfacial interactions between Er and Yb sublattices, resulting in 2 orders of magnitude enhancement in luminescence intensity. We further demonstrate that the IET channels can also mediate up-transition dynamics, which contributes to temporal tuning of real-time red-to-green switchable emission colors. Our findings provide new insights into the upconversion physics involved in the heavy doping nanomaterials and offer new opportunities for infrared photodetection and potentially other photonic applications.