High-k Fluoropolymers Dielectrics for Low-Bias Ambipolar Organic Light Emitting Transistors (OLETs)

Abstract

Organic light emitting transistors (OLETs) combine, in the same device, the function of an electrical switch with the capability of generating light under appropriate bias conditions. In this work, we demonstrate how engineering the dielectric layer based on high-k polyvinylidene fluoride (PVDF)-based polymers can lead to a drastic reduction of device driving voltages and the improvement of its optoelectronic properties. We first investigated the morphology and the dielectric response of these polymer dielectrics in terms of polymer (P(VDF-TrFE) and P(VDF-TrFE-CFE)) and solvent content (cyclopentanone, methylethylketone). Implementing these high-k PVDF-based dielectrics enabled low-bias ambipolar organic light emitting transistors, with reduced threshold voltages (<20 V) and enhanced light output (compared to conventional polymer reference), along with an overall improvement of the device efficiency. Further, we preliminary transferred these fluorinated high-k dielectric films onto a plastic substrate to enable flexible light emitting transistors. These findings hold potential for broader exploitation of the OLET platform, where the device can now be driven by commercially available electronics, thus enabling flexible low-bias organic electronic devices.

TCTA:Ir(ppy)3 Green Emissive Blends in Organic Light-Emitting Transistors (OLETs)

“…The scan size is 10 μm × 10 μm, and the scale bar is 2 μm for all micrographs. Figure 5a shows the typical islandlike structure of C8BTBT grown on the PMMA layer (rms <1 nm), 30 characterized by an extremely flat surface (rms <2 nm), consistent with the growth mechanism reported in the literature. 33 The C8BTBT film exhibits relatively large grain sizes and good connectivity, which is then reflected in the overall high hole mobility value even in the multilayer heterostructure.…”

“…We found values of hole (electron) mobilities of 0.4–1 (0.1–0.25) cm 2 /Vs (see Table ) with seemingly no clear dependence from the doping concentration of the emissive blend (see later in the manuscript). These values are less than 1 order of magnitude smaller compared to the corresponding single-layer organic field-effect transistor based on each semiconductors; for this, we refer the reader to one of our recent studies using the same set of materials . Threshold voltages are found in the range of −|40–50| and 49–52 V for holes and electrons, respectively.…”

“…These values are less than 1 order of magnitude smaller compared to the corresponding single-layer organic field-effect transistor based on each semiconductors; for this, we refer the reader to one of our recent studies using the same set of materials. 30 Threshold voltages are found in the range of −|40− 50| and 49−52 V for holes and electrons, respectively. These values are consistent with organic light-emitting transistors using low-k PMMA as a dielectric layer, 31 and no correlation with the doping concentration is found.…”

Ferroelectrics‐Electret Synergetic Organic Artificial Synapses with Single‐Polarity Driven Dynamic Reconfigurable Modulation

“…For the terpolymer, a typical rice grain‐like structure is found (Figure 1c(i)), which is a well‐known characteristic of P(VDF‐TrFE‐CFE)‐based formulation for polymerization procedures at a temperature below the paraelectric temperature. [ 36,37 ] The ferroelectricity of the P(VDF‐TrFE‐CFE) dielectric layer was further confirmed by the polarization‐electric field ( P ‐ E ) hysteresis loop based on the capacitor of Al/P(VDF‐TrFE‐CFE)/Al at a constant frequency of 1000 Hz in Figure S2 (Supporting Information). In addition, we measured the ferroelectricity of PVDF using PUND (positive‐up‐negative‐down) test mode, which shows a residual polarization voltage ( P r ) of 5.1 mC m −2 .…”

Hafnium Aluminate–Polymer Bilayer Dielectrics for Organic Light-Emitting Transistors (OLETs)

“…Glass/ITO substrates were cleaned in an ultrasonic bath in diluted Hellmanex III followed by deionized (DI) water, acetone, and 2-propanol as described in our previous work . Prior to dielectric polymer deposition, substrates were treated with oxygen plasma (100 W for 15 min).…”