Nondoped Blue Organic Light Emitting Devices with Donor−π–Acceptor Derivatives as the Emissive Material

Abstract

Blue emitting devices based on donor–linker–acceptor geometry such as p-methoxynaphthylphenanthroimidazole–phenyl–phenylbenzenamine (TPA–MPI) and p-methoxynaphthylphenanthroimidazole–styryl–phenylbenzenamine (TPA–MPS) were synthesized and characterized. Due to the rigid molecular backbone composed of phenanthro­[9,10-d]­imidazole (acceptor), phenyl (TPA–MPI) and styryl (TPA–MPS) spacers, and triphenylamine (donor), these compounds exhibit good thermal stability. The nondoped device based on TAP–MPS exhibits higher efficiencies, 1.73 cd A–1 (ηc), 1.46 lm W–1 (ηp), and 2.11% (ηex). The higher efficiency is attributed to the coemission from the intercrossed excited state of the emissive layer.

Hybridised-Local and Charge-Transfer Excited States in Donor-Spacer-Acceptor Molecules for Efficient OLEDs: Combined Experimental and Theoretical Study

“…The para ‐linked p TPA‐MPPPI shows excellent electroluminescent efficiencies (μ c ‐ 3.10 cd/A; μ p ‐ 3.94 lm/w and μ ex ‐ 4.05%). Compared to our previous results, the para‐linked TPA–MPPPI based device show higher efficiencies with low turn‐on voltages because of the rigid phenanthro[9,10–d]–imidazole plane of para‐linked TPA–MPPPI. The inferior performance of the MPPPI device probably derive from the close packing of the MPPPI molecules in the light‐emitting layer and the strong intermolecular interactions at the interfaces, as a result of the planar structure of MPPPI.…”

Robust luminogens as cutting-edge tools for efficient light emission in recent decades

“…Jayabharathi et al 143 synthesized D–π–A materials with HLCT behaviour (TPA-MPI-phenyl spacer/TPA-MPS-styryl spacer), which exhibited excellent optical properties [ λ abs s,f : 396, 398/391, 392 nm; PL s,f : 466, 468/445, 446 nm; PLQY s,f : 70, 70/75, 75%; τ : 2.61/2.53 ns; T m , T g , T d : 281, 130, 442/298, 139, 451 °C; and HOMO, LUMO: 5.04, 2.31/5.25, 2.60 eV, respectively]. Due to the longer conjugation length, the π–π* transitions led to a higher extinction coefficient, enabling a reduction in the film thickness.…”

A Review on the Milestones of Blue Light-Emitting Materials in India

“…The styryl spacer containing the TPA-MPS device exhibited the current efficiency at 1.73 cd/A, power efficiency (PE) at 1.46 lm/W, and provided 2.11 % EQE with 4.6 V. Both the reported emitters TPA-MPI and TPA-MPS (Figure 18) acted as a potential blue candidate for OLEDs. 45 Although there have been many metal-based complexes, Urinda et al synthesized Ir (II)-based N^N and C^N complexes (Figure 19). They aimed to provide different types of molecules which can have excellent relative effectiveness.…”

“…46 As per the literature survey, the blue OLED device started with only 15.8 % EQE in 2012 and reached to a record high EQE of almost 27.2 % in 2016. The EQE and wavelength for the reported blue emitter are shown below in Table 3 [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] from the year 2010 to 2016.…”

“…The styryl spacer containing the TPA-MPS device exhibited the current efficiency at 1.73 cd/A, power efficiency (PE) at 1.46 lm/W, and provided 2.11% EQE with 4.6 V. Both the reported emitters TPA-MPI and TPA-MPS ( Figure 18 ) acted as a potential blue candidate for OLEDs. 45…”