Nondispersive hole transport in a spin-coated dendrimer film measured by the charge-generation-layer time-of-flight method

Measurements of the mobility of a first-generation $(G1)$ bis-fluorene cored dendrimer have been performed on spin-coated samples of 500 nm thickness using the charge-generation-layer time-of-flight (TOF) technique. A 10 nm perylene charge generation layer was excited by the 532 nm line of a Q-switched Nd:YAG laser and the generated carriers swept through the dendrimer film under an applied field. We observe nondispersive hole transport in the dendrimer layer with a room-temperature mobility $μ=2.0×10−4 cm2/V s$ at a field of 0.55 MV/cm. There is a weak field dependence of the mobility and it increases from $μ=1.6×10−4 cm2/V s$ at 0.2 MV/cm to $μ=3.0×10−4 cm2/V s$ at 1.4 MV/cm. These results suggest that the measurement of mobility by TOF in spin-coated samples on thickness scales relevant to organic light-emitting diodes can yield valuable information, and that dendrimers are promising materials for device applications.