Analysis on carrier trapping mechanism in organic diodes by charge modulation spectroscopy and electric field optical second harmonic generation measurement

We studied electric field distribution changes induced in the active layer of ITO/PI/TIPS-pentacene/Au diodes by carrier injection. Upon application of a step voltage to the diodes, the electric field change across the TIPS-pentacene layer was measured. Significant electric field distribution change was suggested due to the carrier injection, and a simple model that accounts for the I-V characteristics of the diodes was proposed, on the basis of the Maxwell-Wagner model. By using charge modulation spectroscopy (CMS) and time-resolved electric field induced optical second harmonic generation (TR-EFISHG) measurements, we studied the carrier trapping mechanism in ITO/PI/TIPS-pentacene/Au diodes. Using TR-EFISHG in combination with CMS is a very effective way to study carrier behaviors in diodes, and stress-biasing effect induced in TIPS-pentacene active layer can be well identified, in terms of carrier injection and interfacial carrier accumulation.