Defect induced tunable light emitting diodes of compositionally modulated zinc gallium germanium oxides

To circumvent the large global demand of around similar to 15% of the total power requirements just for electric lighting, there is an urgent need of devolving cost-effective rare earth free phosphor-converted white light emitting diodes (pc-WLEDs). Here, we report a defect-induced long and brightly emitting rare-earth free ZnGa2O4 (ZGaO) with PLQY similar to 19%, which could also be successfully excited with ionizing X-rays and electric currents. ZGaO also displayed persistent light for more than an hour endowed by a large density of antisite defects. The defects were further engineered in ZGaO by reacting it with different percentages of Ga2O3/GeO2 yielding stoichiometric Zn3Ga2GeO8 (S-ZGG), gallium excess Zn3Ga4GeO11 (Ga-ZGG) and germanium excess Zn3Ga2Ge2O10 (Ge-ZGG) of zinc gallo germanate samples. The defect density follows the trend Ge-ZZG > S-ZGG > ZGaO > Ga-ZGG which is directly culminated in achieving a high PLQY of similar to 26% in Ge-ZGG. But a lower defect in Ga-ZGG aided in achieving the finest white light emission with correlated color temperature (CCT) of 4267 K, color rendering index (CRI) of 91, and CIE of (0.3731, 0.3862). Overall, the newly-defined structures designed in this research are providing broadband emissions covering most of the visible spectral zone and obtained from the intrinsic defects of the bulk phosphors. We have further proposed a flexible and rare pathway to engineer such defects that tuned the broadband emission from cold white to the energy efficient warm white lighting. We believe this work is an excellent contribution to resolve the issues of expensive RE doping, doping induced strain, complex organic synthesis, safety concern, and serve as a strategic pathway to design thermally stable and cost effective, on demand rare earth free tunable LED with suitable CCT and high CRI.

Automated summary

This study presents a rare-earth free phosphor material for electric lighting, achieving high photoluminescence quantum yield and high-quality white light emission by manipulating defect density. The findings provide a promising solution to the issues of expensive rare earth doping and complex organic synthesis.