Relaxation dynamics in light emitting diodes based on a poly(3-alkylthiophene) derivative: transient capacitance and transient electroluminescence studies

Relaxation dynamics of light-emitting devices (LEDs) based on a poly(3- alkylthiophene) derivative have been studied from transient electroluminescence (EL) and transient capacitance measurements. Transient EL has been studied by applying a sequence of two voltage pulses. During the time delay between the two voltage pulses, the devices relaxed which has been monitored by measuring the EL during the second pulse. The width and amplitude of the voltage pulse have been varied, so that different initial state of the device can be reached before the device was allowed to relax. The time delay between the two pulses has been varied for different cases to study relaxation processes in the device. Transient capacitance technique was also used to monitor the relaxation processes. The time constants for dielectric relaxation and charge redistribution in the devices obtained from the two studies have been compared.