Spatial Extent of Interaction between Excitons and Polarons in a Bilayer Organic Field-Effect Transistor

Abstract

A major loss mechanism in high intensity organic light-emitting devices is the quenching of excitons in the presence of polarons. In this work, the interaction of excitons in N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) with holes in pentacene is studied in a pentacene/NPB bilayer organic field-effect transistor. Gate-modulated steady-state photoluminescence quenching measurements are performed. The excitons are confined in NPB and the polarons in an ultrathin layer of pentacene at the pentacene/NPB organic heterojunction. It is shown that excitons are quenched by polarons, even if they are located on different materials, provided that the exciton and polaron are separated by a length within which efficient Forster resonance energy transfer can occur. The experimental findings are supported by a steady-state three-dimensional simulation of the gate voltage-dependent exciton−polaron quenching efficiency. The Forster resonant energy transfer radius for exciton−polaron interaction at the pentacene/NPB heterojunction is estimated to be in the range of 2.3−3.0 nm.

Polymer Electrolyte Dielectrics Enable Efficient Exciton-Polaron Quenching in Organic Semiconductors for Photostable Organic Transistors

“…When photogenerated excitons diffuse to the conductive channel, they will be quenched by the "excitonpolaron quenching" effect (Figure 3d). 49,50,53,54 Therefore, few free holes are dissociated from excitons and involved in the conduction channel, resulting in photostable characteristics. According to reports by Kemerink et al, there are two processes of "exciton-polaron quenching": Forster resonance energy transfer (FRET) and charge transfer (CT).…”

“…These localized holes form high-density polarons. , However, there are few polarons in the OFET with a PS dielectric because of its weak polarity. When photogenerated excitons diffuse to the conductive channel, they will be quenched by the “exciton-polaron quenching” effect (Figure d). ,,, Therefore, few free holes are dissociated from excitons and involved in the conduction channel, resulting in photostable characteristics.…”

Suppressing the Intrinsic Photoelectric Response of Organic Semiconductors for Highly‐Photostable Organic Transistors

“…As the ionized polyelectrolyte can bind holes by Coulomb force, the localized holes (i.e., polarons) quench excitons by a nonradiative recombination path, resulting in photoluminescence attenuation. [ 11,27,31–33 ] For example, in 18.8 nm C8‐BTBT microstripes ( Figure a), the photoluminescence intensity is attenuated by ≈42% at a gate bias of − 3 V. We define the attenuation degree of photoluminescence intensity as the relative exciton quenching efficiency ( Q ): [ 27,31 ] $$$$\begin{equation}{\mathrm{Q}} = 1 - \frac{{P{L}_{\mathrm{G}}}}{{P{L}_0}}\end{equation}$$$$where PL G and PL 0 denote the photoluminescence intensity with and without gate bias, respectively. As shown in Figure 2; Figure S7, Supporting Information, the relative exciton quenching efficiency decreases with increasing film thickness, indicating that the EPQ effect is gradually weakened in thick OS microstripes.…”

“…As the ionized polyelectrolyte can bind holes by Coulomb force, the localized holes (i.e., polarons) quench excitons by a nonradiative recombination path, resulting in photoluminescence attenuation. [11,27,[31][32][33] For example, in 18.8 nm C8-BTBT microstripes (Figure 2a), the photoluminescence intensity is attenuated by ≈42% at a gate bias of − 3 V. We define the attenuation degree of photoluminescence intensity as the relative exciton quenching efficiency (Q): [27,31]…”

Broadband white electroluminescence from a dopant-free OLED comprising pure electromer and electroplex emission

“…There can be an effect of exciton polaron interaction in the process of pronounced electromer and electroplex emission over exciton or excimer emission in the presented device. Due to the high density of trapped charges in the organic layers which enables electromer formation, the excitons in those layers can get quenched due to exciton polaron quenching phenomenon [15,45,46]. The formation of excimer in such organic systems is forbidden because large molecule excimers contain only a small component of charge resonance states and the stabilization energy is primarily due to exciton resonance [27,47].…”