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황진효,김채영,조민주,최동훈 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
Two polymeric host materials, P(NmCP) and P(mCP), were synthesized to achieve sky-blue and green-emitting thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs) with high device performance via a solution process. The simple structure polymer host was designed by inserting similar electron donating groups and different cores with phenyl and pyridine units, respectively. The two polymeric hosts exhibited high triplet energies (T1 = 3.04 eV for P(NmCP) and 3.05 eV for P(mCP)), which were sufficiently high to realize blue and green TADF-OLEDs. In brief, solution-processed OLEDs with an emissive layer bearing P(NmCP) as a bipolar electron host exhibited remarkable performance with maximum external quantum efficiency (EQE) of 20.07% in the green-emitting device. In the blue-emitting device, we obtained a maximum EQE of 10.70%, respectively.
이동원,황진효,조민주,최동훈 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
In the past few years, many kinds of host materials such as polymers, large molecules, and small molecules were demonstrated for solution-processable TADF-OLEDs. Among them, uniform molecular dyad can be easily synthesized and purified. Owing to large molecular weight, it can provide good film forming property via solution-process. In molecular dyad structure, we can introduce donor and acceptor moieties, which can be isolated through a non-conjugated cyclohexane spacer. Our objective is to maintain intrinsic molecular properties of donor and acceptor and to give bipolar electronic nature. In this work, a bipolar molecular dyad (e.g. BCzTC) having a cyclohexane spacer was synthesized and applied to TADF-OLEDs. The device performances were compared to those of devices made with corresponding p-type, n-type, and mixed hosts. The OLED devices made with BCzTC as a bipolar host and t4CzIPN as an emitter showed an high external quantum efficiency (EQE) and low roll-off behaviors.
Small Molecules and Polymers for Solution-Processed Thermally Activated Delayed Fluorescence OLEDs
Dong Hoon Choi(최동훈),황진효,김형종,조민주 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2
Thermally activated delayed fluorescence (TADF)-assisted organic materials have attracted considerable attention in the field of organic light-emitting diodes (OLEDs). TADF materials are constructed from pure organic entities without the use of any expensive noble metals, and thus, they are more affordable and have high molecular design flexibility. The maximum performance of vacuum processed TADF OLEDs is reported to be close to 40% in the blue and green regions. Recently, our laboratory is more interested in solution process device materials. In this presentation, I would like to introduce the soluble host and emitter materials (e.g. small molecules and polymers) recently researched and developed at KU- FPL, and the device results to which they are applied. Furthermore, I would like to briefly introduce the contents related to host-free, non-doped TADF-OLED.
김채원,주진환,이지혜,김형종,권나연,황진효,조민주,최동훈 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
Since the researchers found that materials exhibit different optical properties in nano-scale, there were numerous efforts to adopt quantum dot (QD) in various area. In display technology, it is obvious that applying QDs as emitting layer can increase the lifetime and color purity. The problem for commercialization is that QD-based light emitting diode (QD-LED) has not reach proper performance compared with organic-LED. Because the poor performance of QD-LED is derived from its low charge balance due to hole transport material (HTM) with low mobility, new charge transporting materials should be considered as key solution for advanced performance. In this study, we synthesized a polystyrene based new HTM (e.g. P-CzAc), with high mobility and investigated its properties. P-CzAc exhibited much higher hole transport ability (hole mobility = 6.21 x 10<sup>-7</sup> cm<sup>2</sup>V<sup>-1</sup>S<sup>-1</sup>) compared with poly(9-vinylcarbazole) (PVK). Eventually, P-CzAc based QD-LED performed with low turn-on voltage and high efficiency.
Hong Diem Chau,권나연,박수홍,황진효,조승욱,이동원,조민주,최동훈 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
In this report, two isomeric BDT-based copolymers, TTE25 and TTE36, were designed and synthesized. The difference in the linking positions of carboxylates in the thienothiophene unit of TTE25 and TTE36 leads to significant different properties between these two copolymers, including the HOMO level, absorption region and crystallinity. Owing to the good miscibility, and especially, of the broad complementary absorption of the TTE25 and TTE36 blend, mixtures of these two polymers at different composition were applied as the donor for the active layer in PC61BM-based organic indoor photovoltaics (IPVs). Under 1000 lux white LED illumination, the optimized TTE36:TTE25:PC61BM (0.8:0.2:1.0 wt. ratio)-ternary-blend-based IPVs achieved a significant increase of PCE to 11.14% compared to the moderate PCE of 6.72% for those without TTE25. This study demonstrated that blending two isomeric polymers is a promising strategy for realizing high-efficiency IPV devices under indoor light conditions.