ABSTRACT
Micro-LED has attracted tremendous attention as next-generation display, but InGaN red-green-blue (RGB) based high-efficiency micro-LEDs, especially red InGaN micro-LED, face significant challenges and the optoelectronic performance is inevitably affected by environmental factors such as varying temperature and operating current density. Here, we demonstrated the RGB InGaN micro-LEDs, and investigated the effects of temperature and current density for the InGaN RGB micro-LED display. We found that temperature increase can lead to the changes of electrical characteristics, the shifts in electroluminescence spectra, the increase of full width at half maximum and the decreases of light output power, external quantum efficiency, power efficiency, and ambient contrast ratios, while current density increase can also give rise to different changing trends of the varieties of parameters mentioned just above for the RGB micro-LED display, creating great challenges for its application in practical scenarios. Despite of the varying electrical and optical charateristics, relatively high and stable colour gamut of the RGB display can be maintained under changing temperature and current density. Based on the results above, mechanisms on the temperature and current density effects were analyzed in detail, which would be helpful to predict the parameters change of micro-LED display caused by temperature and current density, and provided guidance for improving the performance of InGaN micro-LED display in the future.
ABSTRACT
In this Letter, we have successfully realized the full-color micro-LED display on a single-chip utilizing multi-wavelength multi-quantum wells (MQWs). The epitaxial wafer used for micro-LED array chips is designed with two types of MQWs including In0.1Ga0.9N/GaN and In0.55Ga0.45N/GaN grown by metal-organic chemical vapor deposition (MOCVD). A single-chip broad-spectrum multi-wavelength emission from 620 to 450 nm can be realized by changing the injection current to realize the regulation of carrier injection in the MQWs with different emission wavelengths. And the full-color micro-LED display with uniform brightness can be achieved by adopting the pulse width modulation (PWM) to adjust the duty cycle of micro-LED pixels at different pulse voltages. We expect this study will provide a promising research direction for full-color micro-LED displays, thus effectively avoiding the problems caused during the massive transfer and color conversion.
ABSTRACT
Reversible crystal transformation for phenylhydrazones 1 between the orthorhombic microporous 1-E crystal and monoclinic herringbone 1-Z crystal induced by light and heating has been demonstrated. Other than the inherent single-molecular photoreactivity, the weak intermolecular interactions and loose stacking of porous 1-E crystal favor the efficient solid-state photoisomerization.