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arXiv · 1509.07224

Triplet-Polaron Interaction Induced Upconversion from Triplet to Singlet: a New Way to Obtain Highly Efficient OLEDs

Ablikim Obolda·Qiming Peng·Chuanyou He·Tian Zhang·Jiajun Ren·Hongwei Ma·Zhigang Shuai·Feng Li
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Abstract

The triplet harvesting is a main challenge in organic light-emitting devices (OLEDs), due to the radiative decay of triplet is spin-forbidden. Here, we designed and synthesized two D-A type molecules, TPA-TAZ and TCP. The OLEDs based on them exhibit deep-blue emission and the singlet formation ratios are higher than the simple spin-statistics of 25 %. Specially, a TPA-TAZ-based OLED achieves a maximum EQE of 6.8 %, which is the largest value of the undoped OLEDs with CIE(y)< 0.06 (the EBU blue standard) up to date. Comprehensive experiments eliminate the triplet-harvesting processes of thermally activated delayed fluorescence and triplet-triplet annihilation. Instead, the triplet-polaron interaction induced upconversion from triplet to singlet through one-electron transfer mechanism is proposed, and proven by the magneto-current measurement and quantum chemistry computation. Our results may offer a new route to break through the 25 % upper limit of IQE of fluorescent OLEDs, especially, the deep-blue fluorescent OLEDs.

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Ablikim Obolda, Qiming Peng, Chuanyou He, Tian Zhang, Jiajun Ren, Hongwei Ma, Zhigang Shuai, Feng Li. 2015-09-24. Triplet-Polaron Interaction Induced Upconversion from Triplet to Singlet: a New Way to Obtain Highly Efficient OLEDs. https://arxiv.org/abs/1509.07224

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