Interference-enhanced infrared-to-visible upconversion in solid-state thin films sensitized by colloidal nanocrystals

Publication Type:

Journal Article


Applied Physics Letters, Volume 110, Issue 21, p.211101 (2017)



<p>Infrared-to-visible photon upconversion has potential applications in photovoltaics, sensing, and bioimaging. We demonstrate a solid-state thin-film device that utilizes sensitized triplet-triplet exciton annihilation, converting infrared photons absorbed by colloidal lead sulfide nanocrystals (NCs) into visible photons emitted from a luminescent dopant in rubrene at low incident light intensities. A typical bilayer device consisting of a monolayer of NCs and a doped film of rubrene is limited by low infrared absorption in the thin NC film. Here, we augment the bilayer with an optical spacer layer and a silver-film back reflector, resulting in interference effects that enhance the optical field and thus the absorption in the NC film. The interference-enhanced device shows an order-of-magnitude increase in the upconverted emission at the wavelength of &lambda;&thinsp;=&thinsp;610&thinsp;nm when excited at &lambda;&thinsp;=&thinsp;980&thinsp;nm. At incident light intensities above 1.1&thinsp;W/cm2, the device attains maximum efficiency, converting (1.6&thinsp;&plusmn;&thinsp;0.2)% of absorbed infrared photons into higher-energy singlet excitons in rubrene.</p>