Photoconducting polymer nanocomposites with efficient photogeneration and bipolar transport for optoelectronic applications

Abstract Photoconducting polymer nanocomposites with high electrophotographic sensitivity for both positive (S λ + ) and negative (S λ − ) signs of corona charging (up to 400 m 2 /J in 300–620 nm range) and high charge carrier photogeneration quantum yield (β up to 0.6) are developed on the base of p -conducting (S λ +  ≫ S λ − ) polymer matrices (polyimides (PI), carbazolylcontaining (CzCP) polymers) and n -conducting low molecular mass additive (perylenediimide derivative (PDID)) in aggregated form. For p -composites (PI doped with PDID at content C A up to 50% wt.) the efficient hole photogeneration in PDID absorption band is related to the observed electron transfer from PI donor chain fragments with low ionization potential (I D  = 6.8 eV) to the excited PDID aggregates as acceptors (with affinity E A  = 1.8–2.0 eV). Low S λ − value for p -composites is likely due to potential barrier formation between PDID particles (aggregates and clusters) involved in electron transport network. For n -composites (S λ −  ≫ S λ + ) (CzCP doped also with PDID) high S λ − and β values are explained by the efficient electron photogeneration via excited charge transfer complex (exciplex) between excited PDID molecule as acceptor and CzCP carbazolyl pendant as donor (with I D  = 7.4 eV) as well as electron transport network formation involving PDID particles. As it is only ionization potentials of polymer donor fragments that differ essentially for p - and n -composite, the conclusion is made that charge transfer donor-acceptor interaction in the ground state may be responsible for potential barrier formation between acceptor particles embedded in donor matrix. It is found that films of bipolar sensitive composites (S λ +  ≈ S λ − ) (obtained by mixing p - and n -composites in solution) which have microsegregated structure are characterized by the highest S λ + , S λ − and β values. The photovoltaic effect is investigated for sandwich cells with (Al, ITO) electrodes. The best parameters are found for bipolar composite films (0.5–1.0 μm thick).