Cooperative cationic substitution strategy triggers high blue-light absorptance and near-infrared emission with high quantum efficiency in Cr3+-activated pyroxene-type assembly

Abstract

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) assembled with the broadband NIR-emitting phosphors has been a promising light source for application in agricultural plant lighting, night vision, food analysis and medical diagnosis. But it suffers from a low photoelectric efficiency (<30 %) due to deficiency of phosphors with high internal quantum efficiency (IQE) and strong absorption capacity in the blue spectral region. Herein, a broadband NIR-emitting luminescent material capable of efficient blue to NIR light conversion with still high IQE was developed via the chemical-composition engineering of CaMgGe2O6:Cr3+ using cooperative cationic substitution of Ca2+-Mg2+ by Na + -Ga3+. The emission profiles evolved a red-shift from 839 to 859 nm with the full width at half-maximum (FWHM) extending from 161 nm to 177 nm as the increase of [Na+-Ga3+] pairs. In addition, the IQE can be finely adjusted. Importantly, the blue-light absorption efficiency can be greatly improved to 34.8 % upon pumping by the constant excitation energy. The increased local structural distortion induced by introducing [Na+-Ga3+] pairs has been verified for the main factor causing these desirable optical properties change. Benefiting from the improvement of blue-light absorptance, the fabricated NIR pc-LED device via coating the developed phosphor on a blue LED chip achieved the larger photoelectric efficiency 31.2 %@10 mA compared to the previously reported value of 27.2 %@10 mA. The excellent performance of biomedical imaging and night vision surveillance represented by the assembled NIR pc-LED was demonstrated.