Perovskite Photodetector Integrated with Microfluidics\nfor Low-Level Fluorescence Detection: Toward Self-Powered Biomarker\nSensing

Inorganic\n(cesium) metal halide perovskites have been of extensive\ninterest to the broader scientific community owing to their higher\nstability and breakthrough performance in photoelectric conversion.\nWhile substantial progress has been made in perovskite-based devices,\nthey are increasingly attracting interest as potential candidates\nfor fluorescent-based sensors in biological marker detection and quantification.\nHerein, a self-driven perovskite photodetector for fluorescence detection\nis reported, elucidating controlled charge carrier dynamics under\nthe light matter interaction. The light-induced doping phenomenon,\nresulting from the migration of optically activated ions, generates\nan electric field that enables device operation without external\npower. However, the uncontrolled migration of those ions increases\nthe dark current and reduces the stability of the output current.\nTo address this, we fabricate a vertically stacked FTO/PEDOT: PSS/CsPbBr<sub>2</sub>I/PCBM/Ag photodetector with nonsymmetrical electrode design\nto trigger controlled ion migration upon light illumination, thereby\nimproving the device performance and output stability. The photodetector,\ndriven by induced electric field due to the directional polarization,\nachieves an exceptionally low dark current (∼298 pA), a high\non/off ratio on the order of 10,<sup>5</sup> a responsivity of 202\nmA/W, a high detectivity of 2.5 × 10<sup>11</sup> Jones, and\na fast rise and decay time (190 and 100 μs), all are measured\nat 0 V, surpassing the performance of many similar state-of-the-art\nworks. These insights are crucial for practical applications where\nweak light detection is required, and we demonstrate the integration\nof this detector with a microfluidic chip for fluorescence detection\nfrom quantum dot conjugated beads. The photodetector showcased sufficient\nsensitivity to detect signals from quantum dot solutions as low as\n∼23 nM in a microfluidic channel, highlighting the potential\nfor future self-powered integrated platforms for biomarker sensing\napplications.