Molecular-Layer-Defined Asymmetric Schottky Contacts in Organic Planar Diodes for Self-Powered Optoelectronic Synapses

Abstract

Optoelectronic synapses have been utilized as neuromorphic vision sensors for image preprocessing in artificial visual systems. Self-powered optoelectronic synapses, which can directly convert optical power into electrical power, are promising for practical applications. The Schottky junction tends to be a promising candidate as the energy source for electrical operations. However, fully utilizing the potential of Schottky barriers is still challenging. Herein, organic self-powered optoelectronic synapses with planar diode architecture are fabricated, which can simultaneously sense and process ultraviolet (UV) signals. The photovoltaic operations are facilitated by the built-in potential originating from the molecular-layer-defined asymmetric Schottky contacts. Diverse synaptic behaviors under UV light stimulation without external power supplies are facilitated by the interfacial carrier-capturing layer, which emulates the membranes of synapses. Furthermore, retina-inspired image preprocessing functions are demonstrated on the basis of synaptic plasticity. Therefore, our devices provide the potential for the development of power-efficient and advanced artificial visual systems.

Advanced Bioinspired Organic Sensors for Future‐Oriented Intelligent Applications

“…MoS 2 /pV3D3 Charge trapping [61] Image sharpening Multispectral sensing C 8 -BTBT/F 16 CuPc/PMMA Asymmetric heterojunctions Charge trapping [62] Pattern recognition CDs/silk Charge trapping [63] Facial recognition Organic-inorganic halide PQDs Charge trapping [64] Dynamic recognition P(VDF-TrFE)/Cs 2 AgBiBr 6 Charge trapping [65] a) Poly(d,l-lactic acid)-g-polyacrylic acid/polyethylene glycol. b) Poly{2,2-[(2,5-bis(2-hexyldecyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo [3,4-c]pyrrole-1,4-diyl)dithiophene]-5,5′-diylalt-thiophen-2,5-diyl}: [6,6]-phenyl-C61-butyric acid methyl ester.…”

“…In addition, in order to further imitate the intelligent processing of the retina, it is important to fabricate self-powered artificial optoelectronic synapses through appropriate material and device structure design. [61,62,77] Hao et al demonstrated that a self-powered artificial optoelectronic synapse based on organic asymmetric heterostructures was able to perform image sharpening preprocessing with zero-powered synaptic plasticity (Figure 4b). [62] Semivertical organic asymmetric heterojunction devices based on dioctylbenzothienobenzothiophene (C 8 -BTBT) and hexadecafluorophthalocyanine (F 16 CuPc) exhibited typical photovoltaic responses.…”

“…Wang et al prepared a self-powered organic optoelectronic synapse with asymmetric Schottky contacts by constructing asymmetric ultrathin C 8 -BTBT molecular layers in a single device (Figure 4c). [61] Self-powered optoelectronic synapses not only got image sharpening by the high-pass filter function of the spike-rate-dependent plasticity but also achieved image denoising through spike-amplitudedependent plasticity.…”

“…2) The high energy consumption of devices restricts the density of device integration, which is necessary to develop novel self-powered and ultralow energy consumption devices. [39,61,62,81,82] Finally, in terms of functional application, the complex functions such as image recognition realized by organic optoelectronic neuromorphic sensors still require the help of traditional circuits and software algorithms. Therefore, it is necessary to develop a new artificial vision system based on the integration of sensing, storage, and computing.…”

Low-dimensional optoelectronic synaptic devices for neuromorphic vision sensors

“…Photo-excited electron-hole pairs can significantly impact the conductivity of devices by altering carrier concentration at the semiconductor and interface, which can in turn affect the contact barrier [115][116][117][118][119]. Among the mechanisms of the optical modulation barrier, the metal-semiconductor interface contact barrier is the most common.…”