The electroluminescence intensity of a dodecanethiol-functionalized silver (DT-Ag) NP/ CPB:Ir(mpidmb) 2 (acac) film was increased by about 2.23 times in comparison with that of a control device, CPB:Ir(mpidmb) 2 (acac), due to coupling between excitons of emissive layer and the localized surface plasmon resonance (LSPR) of DT-Ag NPs. The current efficiency of a device with a DT-Ag NPs layer at 100 cd cm À2 (42.3 cd A À1) was 17.0 cd A À1 higher than that of the control device (25.3 cd A À1).The increase in current efficiency in the case of DT-Ag NP-coated devices was strongly related to the energy transfer between radiated light generated from the CBP:Ir(mpidmb) 2 (acac) emissive layer and the LSPR excited by the DT-Ag NPs layer.

SPNCN-Cz device exhibits ηex (3.15%), ηc (2.56 cd A−1), ηp (2.45 lm W−1) with CIE (0.15, 0.07).

The electroluminescent properties of asymmetrically twisted phenanthrimidazole derivatives comprised of fluorescent anthracene or pyrene unit namely, 1-(1-(anthracen-10-yl)naphthalen-4-yl)-2-styryl-1H-phenanthro[9,10-d]imidazole (ANSPI), 1-(1-(pyren-1-yl) naphthalene-4-yl)-2-styryl-1H-phenanthro[9,10-d]imidazole (PNSPI), 4-(2-(4-(anthracen-9-yl) styryl)-1H-phenanthro[9,10-d]imidazol-1-yl)naphthalene-1-carbonitrile (ASPINC) and 4-(2-(4-(pyren-1-yl)styryl)-1H-phenanthro[9,10-d]imidazol-1-yl)naphthalene-1-carbonitrile (PSPINC) for blue OLEDs have been analyzed. The asymmetrically twisted conformation interrupt π-conjugation effectively results in deep-blue emission. The pyrene containing PSPINC based non-doped blue device (476 nm) shows maximium efficiencies (current efficiency (ηc)-4.23 cd/A; power efficiency (ηp)-2.86 lm/W; external quantum efficiency (ηex)-3.48%: CIE (0.16, 0.17) at 3.10 V. Among the doped blue devices, An(PPI)2:ASPINC shows high efficiencies (ηc-12.13 cd/A; ηp-5.98 lm/W; ηex-6.79%; L-23986 cd m−2; EL-458 nm) at 3.15 V with CIE (0.15, 0.17) than An(PPI)2:PSPINC based device which is inconsistent with non-doped device performances. The green and red PhOLEDs show higher efficiencies with Ir(ppy)3: ASPINC (ηc-50.6 cd/A; ηp-53.4 lm/W; ηex-17.0%; L-61581 cd m−2; EL-501 nm, CIE (0.31, 0.60) at 3.32 V and (bt)2Ir(dipba): ASPINC (ηc-15.2 cd/A; ηp-16.5 lm/W; ηex-14.5%; L-13456 cd m−2; EL-610 nm), CIE (0.63, 0.36) at 3.20 V, respectively. The complete energy transfer between the host and dopant molecules improved the efficiency of PHOLEDs.

The CADPPI:Ir(ppy)3 device exhibits L – 90 12 cd m−2; ηex – 18.8%; ηc − 27.3 cd A−1; ηp – 29.8 lm W−1; CIE (0.30, 0.60).

Two efficient fluorescent molecules, viz., (E)-2-(2-4-(1-2,3-dihydrobenzo[b][1,4]dioxin-5-yl)-4,5-diphenyl-H-imidazole-2-yl)-[1,1-biphenyl]-4-yl)vinyl-1-yl(naphthalene-1-yl)-1H-phenanthro[9,10-d]imidazole (DDIBNPPI) and (E)-4-(2-(2-(-4′-1(2,3-dihyderobenzo[b][1,4]dioxin-5-yl)-4,5-diphenyl-1H-imidazole-2-yl)-[1,1′-biphenyl]-4-yl)vinyl)-1H-phenanthr[9,10-d]imidazole-1-yl)-1-napthronitrile (DDIBPPIN), were designed and synthesized. DDIBNPPI and DDIBPPIN were obtained by rupturing the covalent bond of phenanthrimidazole core to prevent aggregation-induced quenching. In DDIBPPIN, naphthonitrile group was incorporated into azomethine nitrogen of phenanthrimidazole to enhance charge-transfer ability. The DDIBPPIN/CBP:DDIBPPIN-based device shows blue emission with ηc (current efficiency) of 4.91/4.10 cd/A, ηp (power efficiency) of 4.56/3.84 lm/W, and ηex (external quantum efficiency) of 5.11/5.96%. The ηs (exciton utilization efficiency) values of DDIPNPPI and DDIBPPIN are of 27.0 and 30.3%, respectively. The DDIPNPPI and DDIBPPIN materials employed as a host to fabricate green and red phosphorescent organic light-emitting diodes. The red/white devices (with 0.4% dopant concentration) with DDIBPPIN:Ir(MDQ)2(acac) exhibit maximum L of 69889/26319 cd/m2, ηex of 19.6/16.6%, ηc of 34.6/35.6 cd/A, and ηp of 35.8/36.6 lm/W. The device with DDIBPPIN:Ir(ppy)3/DDIPNPPI:Ir(ppy)3 exhibits green emission [Commission Internationale de l’Eclairage (0.30,0.60)/(0.30,0.60)] with maximum L of 69906/69482 cd/m2, ηex of 17.9/17.0%, ηc of 59.8/58.6 cd/A, and ηp of 63.6/61.3 lm/W. The white device using DDIBPPI:Ir(ppy)3 (with 0.4% dopant concentration) exhibits maximum L of 22152 cd/m2, ηex of 15.8%, ηc of 31.4 cd/A, and ηp of 36.1 lm/W.