Charge-Carrier Dynamics and Exciton-Polaron Quenching Studied Using Simultaneous Observations of Displacement Current and Photoluminescence Intensity

Abstract

Herein, we propose a simple but powerful technique for investigating the correlations between the dynamics of charge carriers and excitons. This technique (DCM-PL) is based on displacement current measurement (DCM) with simultaneous observation of the photoluminescence (PL) intensity. By applying this technique to metal–insulator–semiconductor (MIS) devices incorporating a partial stack of a tris­(2-phenylpyridine)­iridium­(III) [Ir­(ppy)3]-based organic light-emitting diode (OLED), we are able to investigate the hole accumulation behavior and the corresponding PL losses due to exciton-polaron quenching (EPQ). Remarkably, the DCM-PL characteristics revealed that the polarity of the host material in the emission layer modifies the charge-carrier dynamics and EPQ properties. Our results contribute to the optimization of OLED device performance, since EPQ is a key process involved in efficiency roll-off and device degradation.

Simultaneous control of carrier transport and film polarization of emission layers aimed at high-performance OLEDs

“…The 1DPCz-based OLED exhibited a high maximum EQE (EQE max = 26.4%) compared to the mCBP-based OLED (EQE max = 25.3%), while PLQY = 90% of an HDT-1:1DPCz film is lower than PLQY = 95% of an HDT-1:mCBP film. The higher EQE can be attributed to the improved hole transport, resulting in a better carrier balance and/or suppressed exciton quenching by accumulated interfacial charges 11 , 13 , 19 , 34 . We note that these devices were fabricated in the same batch using the method of replacing several shadow masks for the EMLs, meaning that the organic layers, except for the EMLs in each device, are identical.…”

Controlling charge accumulation properties at organic hetero-interfaces using dipolar doping of hole transport layers

“…The reduction in PL intensity was observed in the accumulation state below the device's turn-on voltage, approximately 2 V (Figure 3a). While the doping ratio dependency is not distinctly elucidated, the decrease in PL intensity can be attributed to EPQ resulting from charge accumulation at the interface [4][5][6][7]11,14,15 . This PL intensity reduction was observed for both hole and electron accumulation in Ir(ppy)3-and Alq3-based OLEDs, albeit more prominently in the former 11 .…”

The role of spontaneous orientation polarization on charge storage behavior at an interface between organic semiconductor layers

“…[1][2][3][4][5][6] In particular, in the field of organic light-emitting diodes (OLEDs), an excessive interfacial charge accumulation triggered by the SOP causes device degradation and a decline in electroluminescence (EL) efficiency. [7][8][9][10] Here, the SOP is defined as a phenomenon that is the appearance of polarity by the spontaneous ordering of the permanent dipole moment (PDM) in an organic film (Fig. S1, ESI †).…”