Decay-Length-Guided Electrode Spacing for Wide-Linear-Dynamic-Range CsPbBr3 Nanowire Photodetectors

Abstract

High-performance photodetectors (PDs) operating over an ultrawide irradiance range are essential for sensing, imaging, and optical communication. However, achieving a high linear dynamic range (LDR) remains challenging in low-dimensional PDs, especially at the micro- and nanoscale, where elevated dark current and transport losses limit the detectable irradiance window. In this work, we report that this limitation can be overcome by optimizing the electrode spacing of PDs based on the experimentally determined carrier decay length (L_decay), which was identified as a crucial parameter for realizing high-LDR PDs. Tilted CsPbBr₃ nanowires (NWs) with low-defect density and high stability were grown directly on fluorine-doped tin oxide (FTO) glass substrates. By quantitatively extracting the carrier L_decay through scanning photocurrent microscopy (SPCM), we fabricated interdigitated electrodes with a spacing matched to the measured L_decay on an individual NW to achieve a balance between efficient carrier collection and restrained dark current. The resulting device delivers an ultrahigh LDR of 191 dB (from 1.6 × 10^-8 to 56.8 W cm^-2), despite the active area being reduced to 35.4 μm². Moreover, over 90% of its initial photocurrent was retained after 140 days of storage in a nitrogen-filled environment. This work addresses the challenge of insufficient detection range in micro- and nanoscale low-dimensional PDs, and proposes a practical decay-length-guided electrode-spacing design strategy. This strategy may provide useful guidance for optimizing carrier collection in other low-dimensional photodetectors with similar transport and contact configurations.