Microscale optoelectronic infrared-to-visible upconversion device as the implantable light sources for optogenetics neuromodulation

Photon upconversion with the transformation of low-energy photons to high-energy photons is of significant interest for broad applications. Here, we present self-powered, micrometer-scale optoelectronic devices based on III-V materials for high-performance near-infrared to visible upconversion. By taking advantage of its unique photon - "free electron" - photon processes, these thin-film, ultra-miniaturized devices realize fast upconversion that is linearly dependent on incoherent, low-power excitation, with a quantum yield of ∼1.5%. By exploiting the advanced manufacturing method, encapsulated, freestanding devices are transferred onto heterogeneous substrates and show desirable biocompatibilities within biological fluids and tissues. These devices as the microscale light sources are implanted in behaving animals, with in vitro and in vivo experiments demonstrating their utility for optogenetic neuromodulation. These results provide routes for high-performance upconversion materials and devices and their unprecedented potential as optical biointerfaces.