Infrared-to-visible Upconversion in Light Emitting Diodes and Phototransistors*

Infrared excited and visible emitting upconverting nanoparticles show potential applications in the field of light emitting diodes (LED) and photovoltaics. Despite the fundamental advantages that Upconverting Nanoparticles (UCNPs) have over semiconductor nanoparticles and molecular dyes, they have not been used widely due to their comparatively low brightness and low upconversion efficiency at low pump powers. Existing UCNP devices are based on randomly ordered nanoparticles, which have low external efficiency. The nanoparticles are assembled in a periodic array in order to minimize undesirable scattering and light trapping, thereby increasing the light emission output. We fabricate and characterize a nanoplasmonic upconversion array, including its effect on electric field scattering and enhancement, using our expertise in nanoparticle growth, array nanofabrication, single particle high resolution optical spectroscopy, and finite element modeling.