Highly Efficient Simple‐Structure Blue and All‐Phosphor Warm‐White Phosphorescent Organic Light‐Emitting Diodes Enabled by Wide‐Bandgap Tetraarylsilane‐Based Functional Materials

Two host materials of {4‐[diphenyl(4‐pyridin‐3‐ylphenyl)silyl]phenyl}diphenylamine (p‐PySiTPA) and {4‐[[4‐(diphenylphosphoryl)phenyl](diphenyl)silyl]phenyl}diphenylamine (p‐POSiTPA), and an electron‐transporting material of [(diphenylsilanediyl)bis(4,1‐phenylene)]bis(diphenylphosphine) dioxide (SiDPO) are developed by incorporating appropriate charge transporting units into the tetraarylsilane skeleton. The host materials feature both high triplet energies (ca. 2.93 eV) and ambipolar charge transporting nature; the electron‐transporting material comprising diphenylphosphine oxide units and tetraphenylsilane skeleton exhibits a high triplet energy (3.21 eV) and a deep highest occupied molecular orbital (HOMO) level (‐6.47 eV). Using these tetraarylsilane‐based functional materials results in a high‐efficiency blue phosphorescent device with a three‐organic‐layer structure of 1,1‐bis[4‐[N,N‐di(p‐tolyl)‐amino]phenyl]cyclohexane (TAPC)/p‐POSiTPA: iridium(III) bis(4′,6′‐difluorophenylpyridinato)tetrakis(1‐pyrazolyl)borate (FIr6)/SiDPO that exhibits a forward‐viewing maximum external quantum efficiency (EQE) up to 22.2%. This is the first report of three‐organic‐layer FIr6‐based blue PhOLEDs with the forward‐viewing EQE over 20%, and the device performance is among the highest for FIr6‐based blue PhOLEDs even compared with the four or more than four organic‐layer devices. Furthermore, with the introduction of bis(2‐(9,9‐diethyl‐9H‐fluoren‐2‐yl)‐1‐phenyl‐1H‐benzoimidazol‐N,C³)iridium acetylacetonate [(fbi)₂Ir(acac)] as an orange emitter, an all‐phosphor warm‐white PhOLED achieves a peak power efficiency of 47.2 lm W⁻¹, which is close to the highest values ever reported for two‐color white PhOLEDs.