Visible-to-UV photon upconversion in metal-free molecular aggregates based on glassy diphenylnaphthalene derivatives

Abstract

Visible-to-ultraviolet photon upconversion (UC) based on triplet–triplet annihilation was demonstrated in metal-free glassy solid films consisting of an organoboron photosensitizer and diphenylnaphthalene-based emitter. Upon photoexcitation at 445 nm, UC emissions in the ultraviolet region (370–390 nm) were observed in binary solid films with high UC efficiencies of up to 2.6% and a threshold excitation intensity as low as 44 mW cm⁻².