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

Abstract

As a result of its high carrier mobility and peculiar phase transition, Ag2Se 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 Ag2Se/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.

Flexible High‐Performance Photovoltaic Devices based on 2D MoS2 Diodes with Geometrically Asymmetric Contact Areas

“…[77] The observed symmetric photocurrent in S-MoS 2 agrees with the previous works in the literature. [78][79][80] On the other hand, in the asymmetric geometry device with a rectification of ≈10 5 , the photocurrent has the same polarity for all values of X between the metal contacts and the maximum photocurrent is observed when the laser beam is near the smaller MoS 2 /Cr interface area (Figure 5h), resulting in a non-zero net photocurrent when the entire AS-MoS 2 device is under illumination at zero bias (Figure S16b, Supporting Information). The Schottky barrier at the larger MoS 2 /Cr interface area is sufficiently high to generate a built-in electric field so that all the photogenerated current have the same polarity (negative photocurrent) across the MoS 2 area, even when the laser beam is near the larger MoS 2 /Cr interface area.…”

“…In the S-MoS 2 device (Figure 6a), the V oc changes from negative to positive when the light spot moves from one electrode to the other electrode with a step size of 2 µm, which is due to a well-known phenomenon called the lateral photovoltaic effect (LPE). [77,80] This results in a V oc of about zero when the entire S-MoS 2 device is under illumination. On the other hand, due to a strong built-in electric field in the AS-MoS 2 device, both I sc and V oc increase with the same polarity when the laser moves toward the smaller Schottky barrier (smaller MoS 2 / Cr interface) (Figure 6b).…”

Broadband Self-Powered CdS ETL-Based MAPbI3 Heterojunction Photodetector Induced by a Photovoltaic–Pyroelectric–Thermoelectric Effect

“…Moreover, the response speed of this PD is calculated with the rise and fall times described as the times taken for the output voltage improving from 10 to 90% and descending from 90 to 10% at the laser on and off stage, respectively, as shown in Figure e. Different from that of the previous pyroelectric effect-based devices, − , here the rise and fall times all nearly keep at a constant value of 31 ms in the whole power density range, as shown in Figure f, which may be attributed to the inherent slow transport property of the photovoltaic effect in the perovskite heterojunction due to its long carrier lifetime . However, they are still much better than those of other perovskite heterojunction devices with similar structures, − implying that the pyroelectric effect may also be conducive to the response speed of the CdS/MAPbI 3 /Spiro-OMeTAD heterojunction PD to some extent due to its promotion effect of the carriers’ separation and transport processes.…”

Graphene/Ge Photoconductive Position-Sensitive Detectors Based on the Charge Injection Effect

“…Two-dimensional materials have exhibited unique optical and electrical properties, including high carrier mobility, tunable band structure, and strong light-matter interaction, which make them widely used in the preparation of optoelectronic devices. The photodetectors based on two-dimensional materials have shown excellent performance, including fast speed, high responsivity, and broadband detection [ 15 , 16 , 17 ]. Among them, graphene has attracted intense attention due to its excellent properties, such as mechanical flexibility, high mobility, and layer-tunable band structures [ 18 ].…”