Polarized white light from hybrid organic/III-nitrides grating structures

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.

Host Exciton Confinement for Enhanced Förster‐Transfer‐Blend Gain Media Yielding Highly Efficient Yellow‐Green Lasers

“…Finally, F8BTrelated materials continue to be of strong interest for electrically pumped light emission struc tures [31,32,[41][42][43][44] including LEDs and LETs and it will be interesting to explore how beneficial the blend structure optimization performed here for SE and lasing might be in that context.…”

“…This tendency is also found in the PFO:F8BT films (Figure 4b, peak PLQE = 44% for 5 wt% F8BT) and is typically reported for other FRETcoupled host:guest systems, signaling a tradeoff between the efficiency of FRET and guest selfquenching. [43,44] However, no ASE was detected in PFO:F8BT blends when pumped at 370 nm with pulse energies up to 50 µJ (2330 µJ cm −2 ) irrespective of F8BT fraction. Figure 4c shows the corresponding DBPhFCz:F8BT ASE threshold (E th ASE ) dependence.…”

Efficient Optical Gain from Near‐Infrared Polymer Lasers Based on Poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)]

“…As the PCDTBT content increased, both τ and PLQE experienced a decrease down to 1.19 ns and 0.12, respectively, for the 50 wt% blend, values similar to those found in pristine PCDTBT. This implies the presence of unfavorable interchain interactions in PCDTBT, which limit the gain properties …”

Unraveling the Morphology and Macroscopic Alignment of Poly(9,9-di-n-octylfluorenyl-2,7-diyl) for Enhanced Polarized Emission

“…Conjugated polymers have been largely explored for their potential in electronic devices, − especially in cases where polymer chains can be assembled in a controlled manner. Macroscopic alignment of such chains, for instance, may be exploited in liquid crystal displays, − which is challenging because polymers in solution do not have a planar structure owing to the low rotational energy barrier along their conjugated structure. Despite their rigid molecular structure, conjugated polymers have good self-organization only when concentrated .…”

“…23−26 PFO is semicrystalline with a melting point near 160 °C, above which a nematic (N) phase exists up to 300 °C. 27−32 A number of methods are employed to align conjugated polymers, including the Langmuir−Blodgett 33,34 technique, uniaxial traction in an ultrahigh molecular weight polyethylene matrix, 35,36 nanoimpression through conflation, 11,37 and with an applied flux field. 13 In addition to these relatively complex procedures, molecular ordering of liquid crystals can be obtained using simple techniques.…”