A high-mobility, high-luminescence and low-threshold pentacene-doped cyano-substituted distyrylbenzene crystal†
Organic crystals simultaneously displaying high carrier mobility and high luminescence efficiency are expected to be of interest for the fundamental research of light-emitting devices, and may offer renewed hope for achieving electrical pumping of solid-state organic lasers. However, high charge transport and efficient light emission have been mutually exclusive due to the different inherent natures of their aggregation states in single crystals. Here, we report the successful growth of a pentacene-doped 1,4-bis(2-cyano styryl)benzene (2-CSB⊂Pc) crystal that showed a high carrier mobility of 0.51 cm2 V−1 s−1, efficient emission of red light with a quantum yield of up to 50%, and a low amplified spontaneous emission (ASE) threshold of 46 kW cm−2 using a physical vapor transport (PVT) method. The achieved high carrier mobility was due to the retention of structural order after doping Pc molecules into the 2-CSB matrix, as well as being due to the extensive intermolecular π-orbital overlap stacks in the crystal. The spectral matching between 2-CSB emission and Pc absorption promoted host–guest energy transfer leading to the high luminescence efficiency, and meanwhile, the uniaxially oriented molecular arrangement had the benefit of producing ASE with a low energy threshold. The molecular electronic structures, reorganization energies and orbital overlap integrals were calculated to further elucidate the influences of Pc doping on the luminescence and charge transport characteristics. The primary results indicated that integrated multi-functional optoelectronic crystals can be obtained via a doping strategy, which is of great significance for developing high-performance organic laser materials and devices.