Lateral Photovoltaic Effect-Modulated Visible-Near-Infrared Photodetector Based on Ag-Doped CIGS Heterojunction

With the advancement of intelligent technology and the expanding application fields, high-performance, low-power photodetectors (PDs) have garnered increasing attention. The photovoltaic effect (PVE) is widely regarded as a key mechanism for developing self-powered PD. However, its performance remains constrained due to the limited modulation of longitudinal carrier separation and transport processes. In this work, a lateral PVE (LPE)-based PD was proposed, using an Ag-doped Cu(In,Ga)Se<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub> (ACIGS) heterojunction. While the LPE operates on the foundation of the PVE, it distinguishes itself by incorporating an additional transverse diffusion process, offering a versatile and promising strategy for tuning photoresponse. The results demonstrate that the PD achieves stable and efficient LPE response at zero bias, with the photocurrent showing a linear relationship with increasing laser power. Moreover, the heterojunction has a broad spectral response range, spanning from 405 to 1064 nm. The LPE response is strongly dependent on the laser wavelength, with optimal responsivity (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i><roman xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">)</roman> and detectivity (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i><roman xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">)</roman> of 50 mA/W and 1.32 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>11</roman></sup> Jones, respectively, observed at 780 nm. Owing to the differential carrier collections, when the illumination position gradually moves from the left electrode to the right electrode, the LPE response transitions smoothly from a negative maximum to a positive maximum, diminishing to zero at the midpoint between electrodes. This behavior follows a nearly linear spatial distribution, which can be well explained by the carrier transverse diffusion theory. Additionally, the response speed of the PD was thoroughly investigated. Although the response time decreases rapidly as the pulse frequency increases from 20 to 1000 Hz, it eventually stabilizes at a constant value of 0.07 ms. Importantly, this response time remains unaffected by variations in power density, laser wavelength, and illumination position. This work provides an insight into the development of high-performance PD based on the LPE mechanism in the ACIGS heterojunction.