Enhanced near-infrared light-induced photoresponse via transition of monocrystalline phase and surface reconstruction

Rare-earth-doped upconversion(UC)materials are ideal candidates for solar photovoltaic conversion and NIR response devices due to their unique spectral conversion properties.However,their low efficiency remains a tremendous challenge for practical applications.Here,we constructed an efficient NIR light-responsive device by coating a Si-photoresistor with a transparent gel consisting of UC powders and an organic polymer matrix.We show that reasonable introduction of alkali metal ions(Na+,K+,and Cs+)into the lattice of UC crystals results in the improvement of photoelectricity conversion efficiency,due to the high crystallinity and surface reconstruction caused by alkali metal ion doping.