Tuning the Photoresponse of Nano‐Heterojunction: Pressure‐Induced Inverse Photoconductance in Functionalized WO₃ Nanocuboids

Abstract

Inverse photoconductivity (IPC) is a unique photoresponse behavior that exists in few photoconductors in which electrical conductivity decreases with irradiation, and has great potential applications in the development of photonic devices and nonvolatile memories with low power consumption. However, it is still challenging to design and achieve IPC in most materials of interest. In this study, pressure‐driven photoconductivity is investigated in n‐type WO3 nanocuboids functionalized with p‐type CuO nanoparticles under visible illumination and an interesting pressure‐induced IPC accompanying a structural phase transition is found. Native and structural distortion induced oxygen vacancies assist the charge carrier trapping and favor the persistent positive photoconductivity beyond 6.4 GPa. The change in photoconductivity is mainly related to a phase transition and the associated changes in the bandgap, the trapping of charge carriers, the WO6 octahedral distortion, and the electron–hole pair recombination process. A unique reversible transition from positive to inverse photoconductivity is observed during compression and decompression. The origin of the IPC is intimately connected to the depletion of the conduction channels by electron trapping and the chromic property of WO3. This synergistic rationale may afford a simple and powerful method to improve the optomechanical performance of any hybrid material.

Pressure-induced bandgap engineering and photoresponse enhancement of wurtzite CuInS2 nanocrystals

“…30 The inverse photoconductivity of the WO 3 /CuO nano-heterojunction was induced by a high pressure, accompanied by phase transition and bandgap modification. 35 These results indicate that pressure-induced variations in atomic distance, bandgap, and electronic structure can effectively promote the photoelectric performance of functional materials. In addition, the bandgap of CH-CIS has shown an increasing trend with an increase in the pressure.…”

“…Up to now, pressure-based materials engineering has motivated and strengthened the photoelectrical performances of semiconductive halide perovskites, iodide, sulfides and oxides. 28–35 For example, the perovskite Cs 2 PbI 2 Cl 2 achieved significant photocurrent enhancement at high pressures to regulate the excitonic features. 28 The pressure-treated CH 3 NH 3 SnI 3 exhibited significantly higher photocurrent than its original phase.…”

Self-Assembled Peptide Nanofibers with Voltage-Regulated Inverse Photoconductance

“…NPC with persistent photoresponse is critically needed in realizing optical memories, which can be used in artificial cogni-retina with higher fault tolerance to noise and power surge . Photoelectric properties of NPC may also be used to build sensors that can acquire multidimensional data. , In general, tunable photoconductance within single organic material remains a grand challenge. , …”

“…7 Photoelectric properties of NPC may also be used to build sensors that can acquire multidimensional data. 8,9 In general, tunable photoconductance within single organic material remains a grand challenge. 10,11 Most photoconductance studies in the literature have been focusing on semiconducting materials.…”

Negative Photoconductance Effect: An Extension Function of the TiOx‐Based Memristor

“…The NPC effect, characterized by an increase in resistance under illumination, has been extensively investigated because of its great potential for application in photoelectric detection, nonvolatile memory, and leakage current compensation. [49][50][51] In 1983, the NPC effect was theoretically predicted to exist in semiconductors according to the compensation of minority carriers at the band edge under illumination. [52] Two years later, the NPC effect was observed in a GaAs|AIGaAs heterojunction as a result of elaborate engineering of the compensation process.…”