A simple approach employing energy-down-shift Y3Al5O12:Ce3+ phosphor for realization of flexible white light emitting diodes

摘要

White organic light emitting diodes (WOLEDs) with energy-down structure, in which white light is generated by a combination of blue light-emitting organic light emitting diodes and color conversion layer (CCL) outside of the substrate, have attracted wide attention due to their remarkable advantages in low cost and color stable white light emission. However, low color-conversion efficiency of CCL is still a bottleneck to improve the performance of down-conversion device. It is usually necessary to add additional CCL outside of the substrate, which is the main reason for the reduction of conversion efficiency. In this study, WOLED is implemented by down-conversion scheme, which is based on CCL doped with Y3Al5O12:Ce3+ phosphor into liquid photopolymer. When exposed to ultraviolet light, photopolymer solidifies and forms semi-down-conversion flexible substrates. When the concentration of Y3Al5O12:Ce3+ phosphor in the photopolymer reaches 26 mg ml(-1), the maximum brightness of the device at 11 V reaches 11026 cd m(-2), and the chromaticity coordinates (CIE) at this time are stable in white light isobaric point. Even if the voltage changes from 6 V to 11 V, the CIE chromaticity coordinates only change x = 0.007 and y = 0.012, respectively.