Ultrahigh Detectivity in Spatially Separated Hole/Electron Dual Traps Based Near‐Infrared Organic Phototransistor

Abstract

In phototransistors, the photovoltaic‐induced current is proportional to the turn‐on voltage shift and the total number of trapped charges. However, it is challenging to obtain a high turn‐on voltage shift simply by using minority carrier trap sites because high‐concentration carrier trap sites introduce strong current traps and carrier recombination. In this study, spatially separated, hole/electron, dual traps are introduced into a phototransistor, demonstrating the possibility of combining hole and electron traps without and with illumination, respectively, to obtain a large turn‐on voltage shift. The near‐infrared phototransistor demonstrates a high light‐to‐dark current ratio (1 × 106) alongside a turn‐on voltage shift of 28 V. The current quenching of the charge trap is effectively compensated by the threshold voltage shift, resulting in an increase of the drain–source current. The dual traps induce a low‐noise current and a high photoresponsivity (5.26 × 103 A W–1) under the same gate voltage (Vg = 0 V), exhibiting an ultrahigh detectivity (D1/f∗ = 1.88 × 1015 Jones; Dshot∗= 8.21 × 1016 Jones).

Tunable Photoelectric Properties of n‐Type Semiconducting Polymer:Small Molecule Blends for Red Light Sensing Phototransistors

“…[58,59] If the shot noise from the dark current is the major contributor to limit the detectivity, D * can be expressed as equation ( 3). [32] These key factors of the device under P ill of 3, 1.5, 0.3, 0.15, and 0.03 mW cm -2 and bias of V g = 0 V and V d = 100 V are exhibited in Table 1. By comparing these values, R and ∆V th , as a function of P ill , are plotted in Figure 6a,b, respectively.…”

“…Fullerene derivatives are dominantly selected as the electron acceptors, while many electron donors are available for photodetection layer assembling. [28][29][30][31][32][33][34][35][36][37] However, the fullerenes suffer from insufficient red light absorption, due to their wide Semiconducting blend heterostructures, composed of conjugated polymer with photoresponsive organic crystals, provide an effective way to achieve promising photodetection devices. Here, solution-processed n-type N2200 conjugated polymer and quinoidal thienoisoindigo (TIIQ) small molecule blend is used to construct phototransistors for red light detection.…”

“…Fullerene derivatives are dominantly selected as the electron acceptors, while many electron donors are available for photodetection layer assembling. [ 28–37 ] However, the fullerenes suffer from insufficient red light absorption, due to their wide bandgap and morphological instability. [ 38,39 ] Nam et al.…”

High-Performance Organic Phototransistors Based on D18, a High-Mobility and Unipolar Polymer

“…Most of the recently developed OPTs are based on the hybrid effect, i.e., depositing the organic absorbing layers on high-mobility metal oxides, e.g., ZnO or indium zinc oxide (IZO), , which are inorganic and not flexible. Another strategy is to blend the photosensitive materials within the charge transport channels and form the hybrid layers, − which combine charge generation and charge transfer somehow. For instance, the channels based on BHJs do enhance exciton separation and charge transport, but the conductivity of the channel increased significantly under illumination, which also diminishes the transfer curves of the OPTs severely; that is, the transistors cannot be fully “switched off” by adjusting the gate voltage.…”

Introducing a Surface-Enhanced-Raman-Scattering Enhancer for Experimental Estimation of the Debye Screening Length in Organic Field-Effect Transistors

“…10 Our group has achieved organic phototransistor (OPT) with an ultrahigh response (R > 5.7 × 10 3 A W −1 and G > 1.8 × 10 4 ) in a wide wavelength range (410−740 nm) 11 and a NIR-OPT response showing an ultrahigh detectivity of 1.88 × 10 15 jones at 820 nm. 12,13 Limbu et al have identified the impact of molecular structural properties on the blend energetics and optoelectronic properties. They believed that strong molecular coupling between donor and acceptor molecules in highly intermixed all-small molecule bulk heterojunction blends determines the optoelectronic properties of OPD devices.…”