Transient Current Response Characteristics in MoO₃-Based Organic Light-Emitting Diodes

Abstract

Detailed transient current response characteristics under pulsed voltage in MoO3-based organic light-emitting diodes (OLEDs) are first investigated. The transient current can be divided into three parts: positive current spike (I P), steady-state current (I S), and negative current spike (I N). It is found that I S is the operating current of OLED devices. I P and I N show a linear relationship with pulsed voltage amplitude. Higher I N than I P is induced by the difference of anode Fermi level and highest occupied molecular orbital (HOMO) of NPB. We also derive an expression for duty ratio with space charges. Results show that I P and I N correspond to the charging and discharging processes of space charge, respectively. The current spikes and threshold duty ratio are found only to be affected by the injection barrier and independent of internal device structure.

Charge and exciton dynamics of OLEDs under high voltage nanosecond pulse: towards injection lasing

“…At the end of the voltage pulse, negative current spike occurs before relaxing to zero amps 11 . It has also been observed that the steady-state value of the current during pulse is equal to the current observed in the DC operation mode for the same excitation voltage 12 . This current response can be explained if one models the device with the equivalent circuit presented in Fig.…”

Space charges and negative capacitance effect in organic light-emitting diodes by transient current response analysis

“…However in the discharging process, holes diffuse from the NPB to the anode with no energy barrier, leading to a larger transient current than in the charging process. 24 Both the positive and negative current peaks can be used to calculate the amount of space charges. For the positive I S , it is not easy to decide on the range of integration of the positive current peak.…”

“…In our previous investigations, transient current response characteristics of OLEDs were found to be related to the space charges near electrodes. 24 The space charges charging and discharging processes result in capacitance characteristics. Therefore, in this paper, we will investigate the capacitance characteristics with transient current response.…”

Comparative Study of Red/Green/Blue Quantum-Dot Light-Emitting Diodes by Time-Resolved Transient Electroluminescence

“…29 At the steady state, the responses of the transient current density and transient luminance provide information on the carrier accumulation. 30 After that, the decay of the EL at the end of the applied voltage pulse testifies to the depletion of the charge-carrier reservoir established during the preceding on phase. 31 In some cases, a transient spike after the voltage pulse is turned off reflects charge carrier storage in the EML.…”

“…Next, the rise time ( t r ) of TREL suggests a buildup of the minority carrier density in the recombination zone . At the steady state, the responses of the transient current density and transient luminance provide information on the carrier accumulation . After that, the decay of the EL at the end of the applied voltage pulse testifies to the depletion of the charge-carrier reservoir established during the preceding on phase .…”