Photovoltaic–Pyroelectric Coupled Effect in Ag₂Se/Si Heterojunction for Broad-Band, Ultrafast, Self-Powered, Position-Sensitive Detectors

As a result of its high carrier mobility and peculiar phase transition, Ag 2 Se has been attracting increasing interest for applications that include thermoelectric power generation, solid electrolytes, and resistive random access memory devices. However, the narrow-band gap characteristics and excellent optoelectronic properties of the material are usually neglected or not used well. Here, we report on a simple Ag 2 Se/p-Si heterostructure position-sensitive detector (PSD) based on the lateral photovoltaic effect (LPE) and investigate the optoelectronic properties of this device for the first time. The broad-band performance, ultrafast response speed, and self-powered operation of the PSD are exploited, and the detector’s response performance is improved drastically by coupling of the photovoltaic and pyroelectric effects. A good linearity was observed for the laser position-dependent lateral photovoltage (LPV) response over a wide spectrum from the visible range to the near-infrared region. The effects of illumination power, laser wavelength, and switching frequency on the transient LPV response when modulated by the pyro-phototronic effect were investigated and discussed systematically, with an enhancement ratio of as large as 1797% being achieved. In addition, the response rise/fall times were reduced to 3/5 μs, respectively. The results presented here enable fundamental comprehension of the pyro-phototronic effect-based PSD and provide an accessible route toward the design and performance optimization of such a PSD.