Microscale optoelectronic infrared-to-visible upconversion devices and their use as injectable light sources

Significance Materials and devices that upconvert photons from low to high frequencies are of tremendous interest for broad applications in bio- and chemical sensing, infrared imaging, display, and photovoltaics. Here we develop self-powered, micrometer-scale optoelectronic upconversion devices for infrared-to-visible photon upconversion. The realized microscale optoelectronic device exhibits a practical efficiency of 1.5% under incoherent low-power illumination, with emission intensity linearly dependent on excitation. Other remarkable advances over conventional approaches include broadband absorption, wide-emission spectral tunability (red, yellow, and blue), and fast dynamics. Encapsulated ultraminiaturized devices can be implanted into subdermal tissues and provide stable operation in behaving animals. Demonstrations of optogenetic stimulation in living animals present their potential for biomedical uses. Optical upconversion that converts infrared light into visible light is of significant interest for broad applications in biomedicine, imaging, and displays. Conventional upconversion materials rely on nonlinear light-matter interactions, exhibit incidence-dependent efficiencies, and require high-power excitation. We report an infrared-to-visible upconversion strategy based on fully integrated microscale optoelectronic devices. These thin-film, ultraminiaturized devices realize near-infrared (∼810 nm) to visible [630 nm (red) or 590 nm (yellow)] upconversion that is linearly dependent on incoherent, low-power excitation, with a quantum yield of ∼1.5%. Additional features of this upconversion design include broadband absorption, wide-emission spectral tunability, and fast dynamics. Encapsulated, freestanding devices are transferred onto heterogeneous substrates and show desirable biocompatibilities within biological fluids and tissues. These microscale devices are implanted in behaving animals, with in vitro and in vivo experiments demonstrating their utility for optogenetic neuromodulation. This approach provides a versatile route to achieve upconversion throughout the entire visible spectral range at lower power and higher efficiency than has previously been possible.