Vertical 0D‐Perovskite/2D‐MoS₂ van der Waals Heterojunction Phototransistor for Emulating Photoelectric‐Synergistically Classical Pavlovian Conditioning and Neural Coding Dynamics

Abstract

Optoelectronic‐neuromorphic transistors are vital for next‐generation nanoscale brain‐like computational systems. However, the hardware implementation of optoelectronic‐neuromorphic devices, which are based on conventional transistor architecture, faces serious challenges with respect to the synchronous processing of photoelectric information. This is because mono‐semiconductor material cannot absorb adequate light to ensure efficient light–matter interactions. In this work, a novel neuromorphic‐photoelectric device of vertical van der Waals heterojunction phototransistors based on a colloidal 0D‐CsPbBr3‐quantum‐dots/2D‐MoS2 heterojunction channel is proposed using a polymer ion gel electrolyte as the gate dielectric. A highly efficient photocarrier transport interface is established by introducing colloidal perovskite quantum dots with excellent light absorption capabilities on the 2D‐layered MoS2 semiconductor with strong carrier transport abilities. The device exhibits not only high photoresponsivity but also fundamental synaptic characteristics, such as excitatory postsynaptic current, paired‐pulse facilitation, dynamic temporal filter, and light‐tunable synaptic plasticity. More importantly, efficiency‐adjustable photoelectronic Pavlovian conditioning and photoelectronic hybrid neuronal coding behaviors can be successfully implemented using the optical and electrical synergy approach. The results suggest that the proposed device has potential for applications associated with next‐generation brain‐like photoelectronic human–computer interactions and cognitive systems.

Photoelectric Visual Adaptation Based on 0D‐CsPbBr3‐Quantum‐Dots/2D‐MoS2 Mixed‐Dimensional Heterojunction Transistor

“…[ 1,3 ] Correspondingly, Figure 2b shows a schematic diagram of its energy‐band structures for these three processes. According to the first‐principles calculations, the valence (conduction) bands of CsPbBr 3 ‐QDs and 2D‐MoS 2 flakes are respectively found to be −5.959 eV (−2.228 eV) and −5.858 eV (−4.7472 eV), [ 23 ] indicating that the straddling band alignment heterojunction structure is formed at the CsPbBr 3 ‐QDs/2D‐MoS 2 heterointerface. [ 24 ] In the first process, without external stimulus ( V GS = 0), the MHAT device maintains its original “OFF” state, which is due to the intrinsic heterojunction properties.…”

“…Subsequently, in the next process, the time‐dependent electron‐trapping phenomenon occurs in SCRH, leading to the final decrease of electron concentrations. [ 18,23 ] This process corresponds to a typical adaptation behavior in the MHAT device. [ 1 ] Finally, after the removal of external stimulus, a rapid electron detrapping phenomenon would result in an immediate recovery of the device performance, thus promoting the entire adaptation process.…”

“…This is because the device produces more electrons at the MoS 2 side under a larger stimulus voltage, limiting the trapping ability of SCRH. [ 23 ] Herein, with a fixed stimulus voltage, the relationship between accuracy and d T can be well fitted by using the exponential saturation model as the following equation [ 26 ] where A ∞ , A 1 , and τ are the final value of saturation accuracy, the accuracy amplitude, and the adaptation constant, respectively. Through fitting the data of Figure 3c by Equation (5), the τ can be extracted accordingly as shown in Figure 3d.…”

“…This is because the device produces more electrons at the MoS 2 side under a larger stimulus voltage, limiting the trapping ability of SCRH. [23] Herein, with a fixed stimulus voltage, the relationship between accuracy and dT can be well fitted by using the exponential saturation model as the following equation [26] τ ( )…”

Optogenetics‐Inspired Neuromorphic Optoelectronic Synaptic Transistors with Optically Modulated Plasticity

“…[ 21–23 ] For example, a typical mixed‐dimensional heterojunction based on 0D‐Perovskite/2D‐MoS 2 has been proposed to emulate the optoelectronic synaptic plasticity based on the unique photo‐generated carrier transport through the interface. [ 24,25 ] In neuroscience, the synaptic plasticity is expected to express in a tunable way, known as plasticity modulation, which is crucial to realize highly complicated behaviors of the human organisms. [ 26 ] During the past few years, great efforts have been devoted to realize plasticity modulation in an electrically tunable way such as the gate‐voltage induced inversion between excitatory plasticity and inhibitory plasticity.…”