Photoconductivity and magnetoconductance effects on vacuum vapor deposition films of weak charge-transfer complexes.

Thin films of weak charge-transfer (CT) complexes (pyrene/dimethylpyromellitdiimide or pyrene/pyromellitic dianhydride) were prepared on an interdigitated platinum electrode by vacuum vapor deposition. Their photoconductivity and magnetoconductance (MC) effects were investigated, and mobile triplet excitons (probably CT excitons) were detected by time-resolved ESR (TRESR) at room temperature. The MC effect on the photocurrent was observed and analyzed by quantum-mechanical simulation assuming two types of collision mechanisms between the electron and hole carriers and between the trapped triplet excitons and mobile carriers. A successful simulation was achieved when the parameters (g, D, E, and polarization) determined by TRESR and the effective hyperfine splitting estimated from an ab initio molecular-orbital calculation were used.