Computational Prediction for Singlet- and Triplet-Transition Energies of Charge-Transfer Compounds

Huang, Shuping; Zhang, Qisheng; Shiota, Yoshihito; Nakagawa, Tetsuya; Kuwabara, Kosuke; Yoshizawa, Kazunari; Adachi, Chihaya

doi:10.1021/ct400415r

Cited by 318 publications

(374 citation statements)

References 51 publications

Supporting

Mentioning

347

Contrasting

Order By: Relevance

“…72 However, since one deals here with intramolecular charge-transfer excitations, the E V A (S 1 ) values are systematically overestimated by around 0.8 − 0.9 eV with this functional, in agreement with previous studies. 32 This result clearly reveals how difficult is to tackle efficiently the separation between medium-and longrange effects and its influence on excited-states properties.…”

Section: On the Use Of Double-hybrid Density Functionalsmentioning

confidence: 94%

“…Description, at the TDA-B2GP-PLYP/def2-TZVP//PBE0-D3(BJ)/def2-TZVP level, of the lowest singlet-singlet excitation process (from occupied φ ′ i to unoccupied φ ′ a ) by using NTO and corresponding occupation number λ ia (the threshold for printing occupation numbers is fixed at 0.02), as well as resulting ∆r(NTO) (inÅ) values. 32 ). b Calculated here at the TDA-PBE0/6-31G*//PBE0/6-31G* level.…”

Section: Associated Contentmentioning

confidence: 99%

See 1 more Smart Citation

Theoretical Rationalization of the Singlet–Triplet Gap in OLEDs Materials: Impact of Charge-Transfer Character

Moral

Muccioli

Son

et al. 2014

J. Chem. Theory Comput.

128

143

View full text Add to dashboard Cite

New materials for OLED applications with low singlet-triplet energy splitting have been recently synthesized in order to allow for the conversion of triplet into singlet excitons (emitting light) via a Thermally Activated Delayed Fluorescence (TADF) process, which involves excited-states with a non-negligible amount of Charge-Transfer (CT).The accurate modeling of these states with Time-Dependent Density Functional Theory (TD-DFT), the most used method so far because of the favorable trade-off between accuracy and computational cost, is however particularly challenging. We carefully address this issue here by considering materials with small (high) singlet-triplet gap acting as emitter (host) in OLEDs, and by comparing the accuracy of TD-DFT and the corresponding Tamm-Dancoff Approximation (TDA), which is found to greatly reduce error bars with respect to experiments thanks to better estimates for the lowest singlet-triplet transition. Finally, we quantitatively correlate the singlet-triplet splitting values with the extent of CT, using for it a simple metric extracted from calculations with double-hybrid functionals, that might be applied in further molecular engineering studies.

show abstract

Section: On the Use Of Double-hybrid Density Functionalsmentioning

confidence: 94%

Section: Associated Contentmentioning

confidence: 99%

Theoretical Rationalization of the Singlet–Triplet Gap in OLEDs Materials: Impact of Charge-Transfer Character

Moral

Muccioli

Son

et al. 2014

J. Chem. Theory Comput.

128

143

View full text Add to dashboard Cite

show abstract

“…The zerozero energy of the 1 CT transition was approximately 3.0 eV for 35IPNDCz and 2.9 eV for 26IPNDCz, as determined from their emission onset. 9,15 The corresponding 1 CT bands in the absorption spectra appear as a shoulder around 350400 nm (Figure 2). The photoluminescence quantum yield (PLQY) of 35IPNDCz increases from 0.15 to 0.50 after oxygen degassing by nitrogen bubbling.…”

mentioning

confidence: 99%

“…The amount of CT (q) used to quantify the degree of HOMOLUMO separation was calculated to be 0.85 and 0.88 for 35IPNDCz and 26IPNDCz, respectively, by an orbital composition analysis method reported previously. 9,10 The photophysical properties of 35IPNDCz and 26IPNDCz were investigated in toluene at room temperature (RT). As shown in Figure 2, the broad and structureless emission spectrum was centered at 470 nm for 35IPNDCz and 488 nm for 26IPNDCz; this can be attributed to intramolecular CT from the bicarbazolyl donor to the dicyanobenzene acceptors, as revealed by the DFT results.…”

mentioning

confidence: 99%

Dicarbazolyldicyanobenzenes as Thermally Activated Delayed Fluorescence Emitters: Effect of Substitution Position on Photoluminescent and Electroluminescent Properties

Nomura

Miyazaki

et al. 2013

Chemistry Letters

Self Cite

View full text Add to dashboard Cite

We demonstrate two efficient blue-green thermally activated delayed fluorescence (TADF) compounds comprising a dimeric phenylcarbazole and four cyano substituents on the phenyl rings. A comparison of the 2,6-dicyano-substituted derivative (26IPNDCz) with the 3,5-dicyano-substituted derivative (35IPNDCz) shows that 26IPNDCz provides a larger dihedral angle and a lower decrease in the energy difference between the first singlet and triplet excited states (¦E ST ) and the TADF lifetime. An organic light-emitting diode based on 26IPNDCz afforded an external quantum efficiency of 10% with reduced efficiency roll-off.Organic light-emitting diodes (OLEDs) have attracted much interest recently because of their potential application in flat-panel displays and light sources. In OLEDs containing only fluorescent dyes, the internal quantum efficiency (IQE) is limited to 25% because of the exciton branching ratio of singlet states. Phosphorescent OLEDs containing noble-metal-based phosphors can harvest the remaining 75% triplet excitons and can thus achieve 100% internal quantum efficiency.1,2 However, the drawback of phosphorescent OLED materials is their cost. Recent progress in OLEDs development has focused on lowcost solutions to improve the device efficiency. A promising way is to harvest triplet excitons in fluorescent OLEDs by triplettriplet annihilation (TTA) or thermally activated delayed fluorescence (TADF). TTA comprises intermolecular fusion, in which one singlet and one ground state can be produced from two triplet states. Thus, the upper IQE limit of OLEDs made using TTA can increase to 63% (0.25 + 0.75 © 0.5). Assuming that the optical outcoupling is 0.20, the maximum external quantum efficiency (EQE) is estimated to be 13%. 3 In 2009, the EQE of TTA devices was reported to be 11%, which is very close to the theoretical limit.3 On the other hand, triplets can also be converted to singlets by reverse intersystem crossing (RISC) under thermal activation when the energy difference between the first singlet (S 1 ) and triplet (T 1 ) excited states (¦E ST ) is small enough. 4,5 In 2012, our group demonstrated that an OLED with a green TADF emitter composed of a carbazole donors (D) and a dicyanobenzene acceptor (A) can achieve an EQE as high as 19%, corresponding to an IQE of nearly 100%. 6 At the same time, pure blue and orange-red TADF OLEDs have also achieved high EQEs of 10% and 17.5%, respectively. 7a,7b However, their EQE roll-off at high current density is rather significant because of their long TADF lifetimes. We, thus, investigated the photophysical mechanism of TADF emitters in detail and further demonstrate molecular design principles.According to the Boltzmann statistics, a small ¦E ST is essential for the efficient thermally activated repopulation of the emissive S 1 state; this also governs the TADF lifetime. To achieve a small ¦E ST , a small overlap between the occupied and unoccupied orbitals involved in the excitation is necessary, CT in some cases.9,10 A comparison with the carbazolyldicyanobenz...

show abstract

“…The inclusion of a fix percentage (from ≈20% to ≈50%) of non-local Hartree-Fock exchange (HFexc) in the functional [108] and the use of range-separated hybrid functionals [109][110][111][112][113] are the most commonly employed strategies to practically overcome these drawbacks. Within the latter family, the so called 'optimally tuned' functionals, put forward by Baer, Kronik, and co-workers [114], are grounded on a different idea: the range separation parameter is determined in a non-empirical way, by minimizing the difference between the highest occupied molecular orbital (HOMO) energy (ε HOMO ) and the vertical ionization potential (IP).…”

Section: Organic Dyesmentioning

confidence: 99%

First Principle Modelling of Materials and Processes in Dye-Sensitized Photoanodes for Solar Energy and Solar Fuels

Pastore

2017

Computation

View full text Add to dashboard Cite

Abstract:In the context of solar energy exploitation, dye-sensitized solar cells and dye-sensitized photoelectrosynthetic cells offer the promise of low-cost sunlight conversion and storage, respectively. In this perspective we discuss the main successes and limitations of modern computational methodologies, ranging from hybrid and long-range corrected density functionals, GW approaches and multi-reference perturbation theories, in describing the electronic and optical properties of isolated components and complex interfaces relevant to these devices. While computational modelling has had a crucial role in the development of the dye-sensitized solar cells technology, the theoretical characterization of the interface structure and interfacial processes in water splitting devices is still at its infancy, especially concerning the electron and hole transfer phenomena. Quantitative analysis of interfacial charge separation and recombination reactions in multiple metal-oxide/dye/catalyst heterointerfaces, thus, undoubtedly represents the compelling challenge in the field of modern computational material science.

show abstract

Computational Prediction for Singlet- and Triplet-Transition Energies of Charge-Transfer Compounds

Cited by 318 publications

References 51 publications

Theoretical Rationalization of the Singlet–Triplet Gap in OLEDs Materials: Impact of Charge-Transfer Character

Theoretical Rationalization of the Singlet–Triplet Gap in OLEDs Materials: Impact of Charge-Transfer Character

Dicarbazolyldicyanobenzenes as Thermally Activated Delayed Fluorescence Emitters: Effect of Substitution Position on Photoluminescent and Electroluminescent Properties

First Principle Modelling of Materials and Processes in Dye-Sensitized Photoanodes for Solar Energy and Solar Fuels

Contact Info

Product

Resources

About