The triplet-triplet annihilation process of triplet to singlet excitons to fluorescence in polymer light-emitting diodes

Chitraningrum, Nidya; Chu, Ting Yi; Huang, Pei‐Chen; Wen, Ten Chin; Guo, Tzung‐Fang

doi:10.1016/j.orgel.2018.06.021

Cited by 17 publications

(4 citation statements)

References 43 publications

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“…Specifically, both TCA (e + EX 3 → e′ + S 0 ) and TTA (EX 3 + EX 3 → EX 1 + S 0 ) processes consume EX 3 states, and TTA reduces more EX 3 than TCA. It is well reported that TTA often enhances with increasing the bias current because the number of EX 3 states increases and TTA is proportional to the square of the EX 3 density. ,, After TTA ( C 7 ) is enhanced, less EX 3 participate in TCA, which leads to weakened TCA ( C 6 ), as shown in Figure c.…”

Section: Resultsmentioning

confidence: 90%

Abundant Evolution Processes of Polaron-Pairs and Exciplex States with Various Electron–Hole Coupling Distances in Exciplex-Based OLEDs by Modifying Device Hole-Injection Abilities

Zhao,

Chen,

Cheng

et al. 2023

ACS Photonics

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Intersystem crossing (ISC) and reverse ISC (RISC) between singlet and triplet polaron-pairs (PP) and exciplex (EX) states, triplet-charge annihilation (TCA), and triplet−triplet annihilation (TTA) are well-known key spin-mixing processes in EX-based organic light-emitting diodes (EX-OLEDs) for improving the device optoelectronic performances. These microscopic processes usually show normal current dependencies; i.e., ISC and RISC weaken while TCA and TTA enhance with increasing bias current, respectively. Here, planar-and bulk-heterojunction EX-OLEDs (PHJ-and BHJ-EX-OLEDs) with good and poor hole-injection abilities were fabricated by modifying the device hole-injection layer. Amazingly, electroluminescence (EL) spectra are used to find that electron−hole coupling distances (r) of PP and EX states in PHJ-EX-OLEDs with good and poor hole-injection abilities are short and long, respectively. This unreported phenomenon only exists in PHJ-EX-OLEDs because holes and electrons separately accumulate on different sides of the donor/acceptor interface, and the distance from holes to the interface increases with decreasing hole-injection ability. However, r of PP and EX states in BHJ-EX-OLEDs are always short whether the devices have good or poor hole-injection abilities since holes and electrons are mixed together within the donor:acceptor blend layer. Furthermore, magneto-EL (MEL) traces of these devices are used as fingerprint detection techniques to distinguish various current-dependent ISC, RISC, TCA, and TTA processes of PP and EX states with short and long r. Specifically, current-dependent low-field effects (LFEs, B ≤ 10 mT) of MEL traces from PP and EX states with short r show the abnormal ISC process as the bias current increases (100 → 2000 μA), whereas those from PP and EX states with long r present rich conversions from normal ISC (100 → 400 μA) to abnormal RISC (600 → 1000 μA) and then to normal RISC (1000 → 1400 μA) and finally to abnormal ISC (1600 → 2000 μA) processes. These different current-dependent LFEs occur because PP and EX states with short and long r undergo monotonically and nonmonotonically current-dependent ISC and RISC processes, respectively. Moreover, current-dependent high-field effects (HFEs, 10 < B ≤ 300 mT) of MEL traces from EX states with a short r show the normal TCA process with increasing the bias current (100 → 2000 μA), but those from EX states with long r display an interesting conversion from abnormal TCA (100 → 1000 μA) to normal TTA (1000 → 2000 μA) processes. These different current-dependent HFEs happen because EX states with short and long r separately participate in the monotonically enhanced TCA process and the competition between the TCA and TTA processes. Obviously, this work enriches the physical understanding of the currentdependent ISC, RISC, TCA, and TTA processes of PP and EX states with short and long r in EX-OLEDs.

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Section: Resultsmentioning

confidence: 90%

Abundant Evolution Processes of Polaron-Pairs and Exciplex States with Various Electron–Hole Coupling Distances in Exciplex-Based OLEDs by Modifying Device Hole-Injection Abilities

Zhao,

Chen,

Cheng

et al. 2023

ACS Photonics

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“…3 There are two main types of up-conversion mechanisms that can result in DF: triplet–triplet annihilation (TTA) and thermally activated delayed fluorescence (TADF). 4 The first route, TTA, occurs predominantly in materials with larger singlet–triplet energy gaps, and is mostly observed in concentrated solutions or at low temperatures when aggregates are formed upon cooling. TTA is also often observed in the condensed phase, where conditions to promote collisions between two triplet species are favoured.…”

Section: Introductionmentioning

confidence: 99%

9-Borafluoren-9-yl and diphenylboron tetracoordinate complexes of F- and Cl-substituted 8-quinolinolato ligands: synthesis, molecular and electronic structures, fluorescence and application in OLED devices

et al. 2023

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“…Poly(phenylenevinylene) (PPV) and its derivatives have attracted considerable attention because of their remarkable optical and electronic properties. It is well known that after the discovery of the optoelectronic properties of PPVs, especially the electroluminescence, , these materials have been exploited as an active layer in organic light-emitting diodes (OLEDs) − and other applications such as laser dyes, − photovoltaic cells, − chemosensors, − linkers for metal–organic frameworks (MOFs), − dendrimers, − photoredox catalysts, and photosensitizers. − The synthesis of PPVs frequently presents challenges as it leads to a mixed cis/trans-configuration over the vinyl segments of the polymeric structure; they show large dimensions and poor solubility in a wide range of solvents …”

Section: Introductionmentioning

confidence: 99%

Spectroscopic and Time-Dependent DFT Study of the Photophysical Properties of Substituted 1,4-Distyrylbenzenes

et al. 2019

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In this contribution, we examine the photophysical properties of 15 totally trans–trans 1,4-distyrylbenzene derivatives (DSBs) functionalized with different electron-donating (ED) and electron-withdrawing (EW) groups by experimental and computational methodologies. We use UV–vis and fluorescence spectroscopies to determine the experimental optical properties such as the maximum absorption (λabs exp) and emission (λem exp) wavelengths, the highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) energy gaps (ΔE abs exp), the molar extinction coefficients (ε), the fluorescence quantum yields (Φf), and the fluorescence lifetimes (τ). We also calculate the experimental spontaneous emission decay rate (k r exp) and correlate all of these magnitudes to the corresponding calculated properties, maximum absorption (λabs cal) and emission (λem cal) wavelengths, vertical transition energies (ΔE abs cal), oscillator strength (F osc), and spontaneous emission decay rate (k r cal), obtained by the time-dependent density functional theory method. We analyze the effect of the electronic nature of the substituents on the properties of the DSBs, finding that the ED and EW groups lead to bathochromic shifts. This is consistent with the decrease of ΔE values as the strength of ED and EW substituents increases. We find excellent correlations between calculated and experimental values for λabs, λem, and ΔE abs (r ∼ 0.99–0.95). Additionally, the correlations between the relative ε with F osc values and the k r values are in good agreement (r ∼ 0.88–0.72) with the experimental properties. Overall, we find that for substituted 1,4-DSBs, computational chemistry is an excellent tool to predict structure–property relationships, which can be useful to forecast the properties of their polymeric analogues, which are usually difficult to determine experimentally.

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The triplet-triplet annihilation process of triplet to singlet excitons to fluorescence in polymer light-emitting diodes

Cited by 17 publications

References 43 publications

Abundant Evolution Processes of Polaron-Pairs and Exciplex States with Various Electron–Hole Coupling Distances in Exciplex-Based OLEDs by Modifying Device Hole-Injection Abilities

Abundant Evolution Processes of Polaron-Pairs and Exciplex States with Various Electron–Hole Coupling Distances in Exciplex-Based OLEDs by Modifying Device Hole-Injection Abilities

9-Borafluoren-9-yl and diphenylboron tetracoordinate complexes of F- and Cl-substituted 8-quinolinolato ligands: synthesis, molecular and electronic structures, fluorescence and application in OLED devices

Spectroscopic and Time-Dependent DFT Study of the Photophysical Properties of Substituted 1,4-Distyrylbenzenes

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