A series of single hole devices are designed based on the different c oncentrations of FeCl_3doped in 4,4′-Bis(9H-carbazol-9-yl)biphenyl (CBP).The hole mob ilities of p-type doped CBP by FeCl_3with various doping concentrations are estimated by using space-charge-limited current model,and compared with the mobility of NPB whi ch is a kind of hole transport material commonly used in organic electroluminescence devices .The results indicate that FeCl_3doped CBP has significantly improved hole mobility .The highest hole mobility is achieved when the concentration of FeCl_3is 12%.For an electr ic field of 0.5MV/cm,the estimated hole mobility of FeCl₃-doped CBP with doping concentrat ion of 12% reaches 4.5×10－5 cm²/V·s.Even in zero electric field,the hole mobilit y can reach 2.2×10－5 cm²/V·s,which is nearly four times of that of NPB.High efficiency organic lig ht-emitting device is fabricated by using CBP:12% FeCl_3as the hole transport layer.The device shows a maximum luminance of 68468cd/m^2and a maximum current efficiency of 31.1cd/A,which are increased by 97% and 23% compared with those of the reference device,respectively.The improvements are a ttributed to the balanced charge carrier transport characteristic,which results in an increased charge ca rrier recombination probability and a decreased triplet-polaron (T-P) annihilation p robability.