Material development of photon upconversion based on triplet-triplet annihilation

Abstract

Triplet-triplet annihilation-based photon upconversion (TTA-UC) is a methodology to convert lower energy photons into higher energy photons under low-intensity light. While efficient TTA-UC within the visible range has been achieved, it remains difficult to achieve similar efficiencies in TTA-UC from visible to UV or NIR to visible light. As for visible-to-UV TTA-UC, the discovery of key chromophores has dramatically increased its efficiency, making it possible to generate UV light from sunlight or indoor light. The role of triplet pair intermediates in TTA-UC has also been better understood, and the importance of intermolecular orientation, reverse intersystem crossing, and triplet pair dynamics in achieving high TTA-UC efficiency has been clarified.