Figure1. Spectroscopic properties of QD gain medium and realization of high current injection QLEDs for population inversion. (IMAGE)
Caption
Figure1. Spectroscopic properties of QD gain medium and realization of high current injection QLEDs for population inversion. (a) The PL (red), absorption (black) and absorption second derivative (blue) spectra of the QDs. The arrows mark the 1Se−1Shh, 1Se−1Slh and 1Pe−1Phh transitions. The electronic states of QDs are also shown in the right. (b) The PL spectra as a function of pump fluence. The QDs was spin-coated onto a glass substrate and pumped by 355 nm, 1.7 ns laser at room temperature. The PL spectra exhibit 1S emission at 625 nm, 1P emission at 595 nm and 1S ASE at 639 nm. (c) The 1S PL intensities (green line) and linewidths (yellow line) as a function of pump fluence. At ASE thresholds of 2.6 µJ cm−2, the emission intensity rises rapidly and super-lineally, accompanied by a significant narrowing of FWHM. (d) The dependence of the average QD occupancy <N> on pump intensity calculated considering multiexciton states of the order up to 6. (e) A schematic depiction of the bottom-emitting and top-emitting QLED structures and driving pulse signals. (f) Device temperature as a function of current density. (g) J-V-L curve of the bottom-emitting device. With effective thermal management, the device exhibits an injection current up to 1300 A cm−2. (h) The EL spectra as a function of current density. The EL spectrum at 802 A cm−2 is deconvolved into two Lorentzian bands that correspond to the 1S and 1P transitions.
Credit
Fengshou Tian et al.
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