Electrospun polymer/quantum dot composite fibers as down conversion phosphor layers for white light-emitting diodes†
Color control without severe photoluminescence (PL) quenching is one of main issues in white light emission technology. White light emission was successfully achieved using phosphor layers made of electrospun quantum dot (QD) embedded polymer fibers as color down-conversion layers of blue light-emitting diodes (LEDs). Down-conversion from blue to longer wavelength was characterized by fluorescence microscopy and photoluminescence (PL) spectroscopy. Using orange QD-embedded fiber-based phosphor layers, a broad spectrum of white-light was demonstrated with the CIE coordination of (0.367, 0.367). The QDs in the polymer fiber matrix did not show the aggregation of QDs unlike the QDs in a thin film matrix. Furthermore, from Time-Correlated Single Photon Counting (TCSPC) analysis, the QDs in fiber mats have longer PL lifetime (∼3.95 ns) than that in a thin film matrix (∼3.20 ns) due to the lower aggregation-induced luminescence concentration quenching. Our results suggest that the simple electrospinning method may be a very good method to obtain uniform and bright QD phosphors for white LEDs which can be used for solid-state illumination sources and lighting devices.