Abstract
Charge transport and electronic transition properties of a series of newly designed anthracene-based non-doped blue emitters were investigated by density functional theory calculations. For a highly efficient non-doped device, Cz3PhAn-based emitters were designed to suppress the hole and electron reorganization energies required for structural relaxation with respect to the changes of charged states. As a result, the hole hopping rates of triphenylamine (TPA) and phenylbenzimidazole (PBI) substituted Cz3PhAn derivatives (1, 4, and 5–7) were tremendously enhanced as compared to that of Cz3PhAn due to the suppression of the reorganization energy of holes, λh. Moreover, 1 and 4 emitters showed almost identical hopping rates of holes and electrons, which can possibly lead to a perfect charge balance and high efficiency. The photo-physical properties showed that the emission energy of all 1–10 emitters is in 439–473 nm range. It is expected that our rational design strategy can help develop non-doped blue fluorescent emitters for high efficiency.
Highlights
Since the rst invention of self-emitting devices by Tang et al.,[1] solid state organic light emitting devices have been received tremendous attention in the display industry owing to their wide applications in high quality full-color displays and mechanical exibility.[2,3,4,5] To achieve high efficiency and long lifetime, many attempts have been made utilizing multi-layered organic light emitting diodes (OLEDs).[6,7] In order to achieve high efficiency and long lifetime simultaneously, good charge balance and high internal quantum efficiency (IQE) are essential, resulting in multi-functional materials in multi-layered devices.[8]
We introduce a series of Cz3PhAn derivatives that were designed based on the aforementioned theory and investigate their electronic, charge transport, and photo-physical properties by using density functional theory and time-dependent density functional theory simulations
We carried out the density functional theory (DFT) calculations for Cz3PhAn derivatives using a nonlocal functional of CAMB3LYP27 and double zeta potential basis set with one polarization function (6-31G*) implemented in a suite of Gaussian 09 program.[28]
Summary
Paper improved while maintaining inherent transition properties. As referred to previous reports, the balanced charge carrier concentration can efficiently enhance the generation of excitons, which lead to increased concentration of triplet excitons. The improvement of charge carrier mobility of anthracene based non-doped emitters can enhance the device efficiency due to the increase of TTF. In case of anthracene based non-doped emitter, the charge carrier mobility might be modulated by reducing the reorganization energy. From this perspective, we have rationally analyzed the structural variations of Cz3PhAn via redox reaction. We expect that our designed emitters based on modulation of charge transport property can show excellent device performance via enhanced TTF phenomena in OLED device as compared Cz3PhAn (Fig. 1)
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