The DFT study on non‐conjugated polymer host materials based on styrene derivatives for phosphorescent polymer light‐emitting diodes

Abstract

A series of poly(4,4-vinyltriphenylamine) based non-conjugated polymer as host molecules are designed and studied by density functional theory. The results show that the substituent has a great influence on the properties of polymer. The parent molecule directly linked para-carbazole, β-pyrrole and triphenylamine are favorable to hole injection, and para-carbazole could significantly increase E T of the host molecules. The large changes of structural parameters between the lowest triplet state and ground state can cause the decrease of E T . Moreover, parent molecule directly linked carbazole and triphenylamine units possess strong intramolecular charge transfer and low singlet and triplet energy difference (ΔE ST ). The calculated results also show that all designed host molecules are suitable for green emitter by comparing with the E T . S 1 → S 1 and T 1 → T 1 energy transfer mechanism between host and guest is thermodynamically feasible. In addition, host-guest model is built to study the charge transfer nature, and the results indicate that a good intermolecular charge transfer can be achieved between host and guest materials. In the designed host molecules, the N atom of parent molecule linked para-carbazole substituent shows a great potential for the green phosphorescent polymer light-emitting diodes.

Theoretical Investigations of the Spiro‐Annulated Triphenylamine/ N‐Phenylcarbazole‐Based Ambipolar Host Materials for OLEDs

“…As shown in Figure , in such host−guest systems, the singlet excitation energies of all host molecules are higher than the relevant guest. The formation of singlet excitons generated on the guest is mainly from singlet excitons on the host via S−S FET; the formation of triplet excitons originate from both triplet excitons on the host molecule via T−T DET mechanism and singlet excitons via intersystem crossing (ISC) to the guest . In this context, POSTF and SOSTF with better performance are selected as the host materials for blue PhOLEDs.…”

Rational design of carbazolyl and aryl phosphine oxide (APO) based ambipolar host materials for blue electrophosphorescence: a density functional theory study

“…On the whole, the NTO analyses are in good agreement with the spin density distributions. Many literature reports 47,48 have indicated that large structural distortions between the ground and the triplet states would lead to an increase of the non-radiative transition rate (k nr ) that might cause unfavorable energy loss. The nonradiative decay rate constant (k nr ) from triplet state to ground state can be evaluated according to eqn (3): 48,49…”