High-mobility, high-luminescence and low-threshold pentacene-doped cyano-substituted distyrylbenzene crystal
Organic crystals simultaneously possessing 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 electrical pumping of solid-state organic lasers. However, high charge transport and efficient light emission properties have been mutually exclusive due to their different requirements of the inherent nature of aggregate states in single crystal. Here, we report the successful growth of pentacene-doped 1,4-bis(2-cyano styryl)benzene (2-CSB⊂Pc) crystal that shows a high carrier mobility of 0.51 cm2/Vs, efficient red emission with quantum yield up to 50% and low amplified spontaneous emission (ASE) threshold of 46 kW/cm2 through physical vapor transport (PVT) method. The achieved high carrier mobility comes from the structural-ordering retention after doping Pc molecules into 2-CSB matrix, as well as largely intermolecular π-orbital overlap stacks in the crystal. The spectral matching between 2-CSB emission and Pc absorption promotes host-guest energy transfer leading to the high luminescence efficiency, and meanwhile, the uniaxially oriented molecular arrangement benefits for ASE with a low energy threshold. The molecular electronic structures, reorganization energies and orbital overlap integrals are calculated to further elucidate the influences of Pc doping on the luminescence and charge transport characteristics. The primary results indicate that integrated multi-function optoelectronic crystals can be obtained via doping strategy, which is of great significance for developing high-performance organic laser materials and devices.