Charge transport in a blue-emitting alternating block copolymer with a small spacer to conjugated segment length ratio

We analyze current versus voltage data obtained using single carrier inject ion in several metal/polymer/metal sandwich structures. The polymer used in each case is a soluble blue-emitting alternating block copolymer. Our expe rimental results demonstrate that the electron transport is space-charge li mited by the high density of traps having an exponential energy distributio n (temperature dependent characteristic energy) in the copolymer. The elect ron mobility of 8x10(-10) cm(2)/V s is directly determined using space-char ge-limited current analytical expressions. Hole transport is also space-cha rge limited, with a mobility of 2x10(-6) cm(2)/V s. A hole trap with energy 0.17 eV is observed. We compare these results with those obtained for rela ted block copolymers with different spacer and conjugated segment lengths a nd discuss the influence of spacer length and conjugated segment length on the charge transport properties. (C) 2000 American Institute of Physics. [S 0021-8979(00)04501-1].