Highly spectra-stable pure blue perovskite light-emitting diodes based on copper and potassium co-doped quantum dots

Halide perovskite light emitting diodes(LEDs)have gained great progress in recent years.However,mixed-halide perovskites for blue LEDs usually suffer from electroluminescence(EL)spectra shift at a high applied voltage or current density,limiting their efficiency.In this work,we report a strategy of using single-layer perovskite quantum dots(QDs)film to tackle the electroluminescence spectra shift in pure-blue perovskite LEDs and improve the LED efficiency by co-doping copper and potassium in the mixed-halide perovskite QDs.As a result,we obtained pure-blue halide perovskite QD-LEDs with stable EL spectra centred at 469 nm even at a current density of 1,617 mA·cm^(−2).The optimal device presents a maximum external quantum efficiency(EQE)of 2.0%.The average maximum EQE and luminance of the LEDs are 1.49%and 393 cd·m^(−2),increasing 62%and 66%compared with the control LEDs.Our study provides an effective strategy for achieving spectra-stable and highly efficient pure-blue perovskite LEDs.

A Ga-doped ZnO transparent conduct layer for GaN-based LEDs

An 8μm thick Ga-doped ZnO（GZO） film grown by metal-source vapor phase epitaxy was deposited on a GaN-based light-emitting diode（LED） to substitute for the conventional ITO as a transparent conduct layer（TCL）. Electroluminescence spectra exhibited that the intensity value of LED emission with a GZO TCL is markedly improved by 23.6%as compared to an LED with an ITO TCL at 20 mA.In addition,the forward voltage of the LED with a GZO TCL at 20 mA is higher than that of the conventional LED.To investigate the reason for the increase of the forward voltage,X-ray photoelectron spectroscopy was performed to analyze the interface properties of the GZO/p-GaN heterojunction.The large valence band offset（2.24±0.21 eV） resulting from the formation of Ga_2O_3 in the GZO/p-GaN interface was attributed to the increase of the forward voltage.