Time-Resolved Operando Spectroscopic Measurements for Organic Field-Effect Transistors

Time-resolved in situ spectroscopic measurements are performed to optically probe the operation process of organic field-effect transistors (OFETs) by combining spectroscopic techniques with gate bias application. The absorption of gate-induced carriers is measured simultaneously in the time domain with the drain current under drain bias application. The growing process of carrier signals is found to compete with its flight process between the source/drain electrodes. The model we propose reproduces well the current transient, consistent with the rising process of carrier signals and determines the flight time of the carrier. The result of the analyses is further developed to elucidate the microscopic nature of the carriers and classify the dynamics and threshold voltages of the two types of carriers generated under FET operation.