Near-infrared-to-deep-blue photon upconversion engineered from PbS quantum dots and perylene derivatives.

Near-infrared (NIR)-to-visible light triplet-triplet annihilation photon upconversion (TTA-UC) holds great promise for solar energy harvesting, photochemistry, and bioimaging. However, achieving a large apparent anti-Stokes shift from the NIR to the blue region remains highly challenging. Here, we present the first TTA-UC system that can upconvert NIR excitation beyond 800 nm with emission approaching the deep-blue spectral region. This performance is realized by precisely engineering the triplet energy levels within only 0.06 eV among PbS quantum dots (QDs) as sensitizers, perylene-3-carboxylic acid (3-PYCA) as a novel mediator and perylene as an annihilator. The system exhibits an exceptional anti-Stokes shift of up to 1.3 eV, representing both a record performance to date and the maximum for QD-based TTA-UC systems. Meanwhile, a high TTA-UC quantum yield of 2.1% (out of a 50% maximum) is achieved, which is an order of magnitude higher than that of previously reported QD-based systems exhibiting anti-Stokes shifts above 0.8 eV. Moreover, the upconverted deep-blue light enables efficiently activated -to- photoisomerization of azobenzene (Azo), demonstrating the high potential in NIR light triggered photochemical transformation.