Phosphorescent Carbene-Gold-Arylacetylide Materials as Emitters for Near UV-OLEDs

A series of carbene-gold-acetylide complexes [(BiCAAC)AuCC]nC6H5-n (n = 1, Au1; n = 2, Au2; n = 3, Au3; BiCAAC = bicyclic(alkyl)(amino)carbene) have been synthesized in high yields. Compounds Au1-Au3 exhibit deep-blue to blue-green phosphorescence with good quantum yields up to 43% in all media. An increase of the (BiCAAC)Au moieties in gold complexes Au1-Au3 increases the extinction coefficients in the UV-vis spectra and stronger oscillator strength coefficients supported by theoretical calculations. The luminescence radiative rates decrease with an increase of the (BiCAAC)Au moieties. The time-dependent density functional theory study supports a charge-transfer nature of the phosphorescence due to the large (0.5-0.6 eV) energy gap between singlet excited (S1) and triplet excited (T1) states. Transient luminescence study reveals the presence of both nonstructured UV prompt-fluorescence and vibronically resolved long-lived phosphorescence 428 nm. Organic light-emitting diodes (OLED) are fabricated by physical vapor deposition with 2,8-bis(diphenylphosphoryl)dibenzo[b,d]furan (PPF) as a host material with complex Au1. The near-UV electroluminescence is observed at 405 nm with device efficiency of 1% while demonstrating OLED device lifetime LT50 up to 20 min at practical brightness of 10 nits, indicating a highly promising class of materials to develop stable UV-OLEDs. Carbene-gold-acetylide (CMAc) complexes are bright deep-blue and green phosphorescent emitters with quantum yields up to 43% which also show UV prompt-fluorescence. Organic light-emitting diodes based on CMAc emitters show near-UV electroluminescence with a device efficiency of 1% and a device lifetime LT50 up to 20 min at practical brightness.image