Capacitance-voltage measurements of hetero-layer OLEDs treated by an electric field and thermal annealing

Abstract

"Abstract: Capacitance-voltage (C-V) characterization of organic light-emitting diodes (OLEDs) having the structure ITO/ PVK (poly (9-Vinylcarbazole)/Rhodamine B dye/Pb is reported. The C-V curves provide more understanding about processes occurring in OLEDs like the voltages at which holes and electrons start flowing from the two electrodes through the OLED layers and the voltages at which emission starts. The OLEDs were fabricated under the same annealing conditions with an additional standard device without annealing for comparison. After depositing the Rhodamine B dye layer on the PVK thin film, samples were thermally annealed at different temperatures. The Pb layer was then deposited. Some samples were thermally annealed without applying any field, while others were annealed at the same temperatures under an external electric field. It was found that devices treated by only thermal annealing and those annealed under an electric field do not show any light emission whereas the standard device fabricated without any annealing does. The main difference between devices fabricated by exposure to an electric field while annealing and other devices is the lower turn-on voltages of the former devices."