Singlet Generation from Triplet Excitons in Fluorescent Organic Light-Emitting Diodes

Abstract

A potential major drawback with organic light-emitting devices, (OLEDs) is the limit of 25% singlet exciton production through spin-dependent charge recombination. Recent device results, however, show that this limit does not hold and far higher efficiencies can be achieved in purely fluorescent-based systems (Wohlgenannt et al. (2012)). Here, the various routes by which triplet excitons can generate singlet states are discussed and their relative contributions to the overall electroluminescence yield are given. The materials requirements to obtain maximum singlet production from triplet states are discussed. These triplet contributions can give very high device yields for fluorescent emitters, which in the case of blue devices can be highly advantageous. Further, new devices architectures open up which are simple and have intrinsically low turn on voltages, ideal for large-area OLED lighting applications.

Recent progress of high performance polymer OLED and OPV materials for organic printed electronics

“…It was also shown that approximately 20% of the device efficiency originated from the production of singlet excitons by TTA in the fluorescent conjugated polymer OLED using F8-PFB and an interlayer of F8-TFB [41]. A similar phenomenon was observed in a polymer OLED with a spirofluorene derivative [42]. This mechanism yielded a very high emission efficiency of 10% EQE with y = 0.13 in a blue-emitting device [43].…”

38-2:Invited Paper: Latest Progress and Its Fundamentals for Polymer-OLED Material

“…It was also shown that approximately 20% of the device efficiency originated from the production of singlet excitons by TTA in the fluorescent conjugated polymer OLED using F8-PFB and an interlayer of F8-TFB [5]. A similar phenomenon was observed in a polymer OLED with a spiro-fluorene derivative [6]. This mechanism yielded a very high emission efficiency of 10% EQE with y = 0.13 in a blue-emitting device [7].…”

Identifying efficient blue-phosphorescent polymer light-emitting diode host materials based on carbazole derivatives with C/Si-centered substituents using density functional theory

“…We have seen that a small ΔE ST can be obtained by replacing the central Si atom of the substituent with a C atom, which leads to a low radiative decay rate according to Fermi's golden rule [46]. Overall, the molecules which the central atom is Si has a suitable ΔE ST .…”