Solution-Processed Vertical Field-Effect Transistor with Separated Charge Generation and Charge Transport Layers for High-Performance Near-Infrared Photodetection

Abstract

The vertical field-effect phototransistor (VFEPT) has received great attention because of its large current density and the low operation voltage required to achieve the desirable photodetector performance. The design of the device architecture and selection of the fabrication method play a vital role in obtaining a high-performance phototransistor that can be manufactured at a scale. Here, we present a highly efficient, all-solution-processable VFEPT based on PbSe quantum dots, in which the charge generation and charge transportation layers (CGL and CTL) are separated by a porous silver nanowire electrode and an ionic gel layer, and the CG efficiency and CT efficiency can be modified independently for near-infrared photodetection. The phototransistor performance is greatly enhanced by a field effect from the CGL that facilitates charge injection into the CTL. The maximum responsivity and the detectivity of the photodetector are 28 A W −1 at −0.75 V SD and 1.3 × 10 13 Jones at 0.5 V SD under a low bias voltage of 1 V GS using 1064 nm illumination.

Electrolyte‐Gated Vertical Transistor Charge Transport Enables Photo‐Switching

“…We argue that V GS increases the charge carrier accumulation at the ZnO/AgNW interface through field-effect phenomena, causing a faster fill of traps. In Figure 7a-c, a hypothesis is presented to interpret the phenomenon found in this work in terms of a model proposed by Subramanian et al [37] Figure 7a,b shows that the charge carrier accumulation due to V GS > 0 shifts the ZnO conduction band energy level leading to a thicker depletion region in the active layer band diagram. Such a change in the conduction band energy results in a lower effective Schottky barrier height once tunneling can occur.…”

“…Even more decisively, we argue that the comprehension of the charge transport dependence on the gate's electric field will undoubtedly be insightful for the next generation of phototransistor‐ and radiation‐sensor applications of EGVFETs. [ 37 ] The ability to control the transistor channel through photo‐switching not only relies on the intrinsic properties of the materials but also on understanding charge transport mechanisms at interfaces and in the bulk. For example, the electrical current flow through ZnO is significantly affected by factors, such as the high density of defect states that can promote trapping and de‐trapping processes, thereby reducing the mobility and lifetime of the photogenerated carriers.…”

Recent Advances in Organic Phototransistors: Nonvolatile Memory, Artificial Synapses, and Photodetectors

“…Therefore, a vertical structure can improve the storage efficiency of nonvolatile memory, [57,58] reduce the power consumption in artificial synapses, [59,60] and be more conducive to realizing ultrafast photoresponse in photodetectors. [61,62] In addition, a vertical OFET is more favorable than a lateral OFET in large-scale integration through crossbar stacking, and a vertical OFET is more tolerant of channel defects and cracks. This defect tolerance implies its potential in flexible device applications.…”

“…2) The adoption of a vertical structure can shorten the length of the charge transfer channel from tens of micrometers to the order of nanometers, effectively reducing the trapped charge leakage and eventually allowing for multilevel storage with high discrepancies and long-term retention characteristics. [57][58][59][60][61][62] 3) Most organic molecules cannot absorb in the IR band, which is critical for data encryption technology. Using upconversion NCs, high-energy photons can be emitted at the expense of two or more low-energy photons.…”