Abstract
Highly polarised white light emission from a hybrid organic/inorganic device has been achieved. The hybrid devices are fabricated by means of combining blue InGaN-based multiple quantum wells (MQWs) with a one-dimensional (1D) grating structure and down-conversion F8BT yellow light emitting polymer. The 1D grating structure converts the blue emission from unpolarised to highly polarised; Highly polarised yellow emission has been achieved from the F8BT polymer filled and aligned along the periodic nano-channels of the grating structure as a result of enhanced nano-confinement. Optical polarization measurements show that our device demonstrates a polarization degree of up to 43% for the smallest nano-channel width. Furthermore, the hybrid device with such a grating structure allows us to achieve an optimum relative orientation between the dipoles in the donor (i.e., InGaN/GaN MQWs) and the diploes in the acceptor (i.e., the F8BT), maximizing the efficiency of non-radiative energy transfer (NRET) between the donor and the acceptor. Time–resolved micro photoluminescence measurements show a 2.5 times enhancement in the NRET efficiency, giving a maximal NRET efficiency of 90%. It is worth highlighting that the approach developed paves the way for the fabrication of highly polarized white light emitters.
Highlights
The last twenty years have seen unprecedented progress in developing white light emitting diodes (LEDs) based on III-nitride blue LEDs1, leading to the solid-state lighting revolution and massive energy savings
The most important feature for such a hybrid white LED using a light emitting polymer as a down conversion material is due to significant potentials to enhance the efficiency of color conversion, which can be achieved through a non-radiative resonant energy transfer (NRET) process, namely, non-radiative Förster energy transfer[5,12,13,14]
We report a different but efficient nanofabrication technique for the fabrication of a 1D grating structure on a standard InGaN/GaN multiple quantum wells (MQWs) structure which can convert unpolarized blue light to polarized light as a result of the 1D grating structure
Summary
A standard InGaN/GaN MQW epi-wafer was used to fabricate the grating structures. A standard reactive ion etching (RIE) using CHF3/Ar gasses was used to transfer the patterns into the SiO2 as a second mask for further etching through the InGaN MQWs by inductively coupled plasma etching (ICP) with Cl2/Ar gasses in order to form the final 1D grating structures. For Time-resolved micro photoluminescence (μ-TRPL) measurements, the above micro-PL system equipped with a time-correlated single photon counting (TCSPC) system was employed. This system is equipped with a 375 nm pulsed diode laser with a 50 picoseconds (ps) pulse width as an excitation source. The identical objective lens described above was used to focus the laser beam
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