Abstract
We report the observation of mobility enhancement of electroluminescent polymer aggregates in as-prepared films and films after electrical annealing by conductingatomic force microscopy (CAFM). With the use of gold-coated AFM tips, local current-voltage curves were measured directly on isolated aggregates and films. Themobility was then determined with space charge limited current (SCLC) theory, and its relationship with the electric field was analyzed by Poole-Frenkel (P-F) law. Onnanoscale aggregates in as prepared-films, the zero-field mobility was found to be 3 orders of magnitude higher than reported macroscopic results, but the field coefficient was in reasonable agreement. On films with a thickness of 25 nm, electrical annealing was performed by repeated scanning on a surface area. It was found that the local current increased by 10 times after 3 repeat scans, whereas no change in surface topography was noticed. The observed mobility enhancement is an indication of the stronger inter-chain interaction in the samples compared to as-prepared films.