# Design and fabrication of a zero-bias visible light photodetector based on a coumarin-derived Schiff base thin film

## TL;DR

A new self-powered visible light photodetector was made using a coumarin-based compound, showing fast response and high efficiency without needing external power.

## Contribution

A novel zero-bias photodetector using a coumarin-derived Schiff base thin film is developed with rapid response and high performance metrics.

## Key findings

- The photodetector achieved a responsivity of 12.6 mA W−1 and detectivity of 9.31 × 10¹⁰ jones.
- The device exhibited a rectification ratio and a linear dynamic range of 35.94 dB under zero bias.
- Spin-coated thin films of 4-FMCSB showed rapid photo response with rise and fall times of 510 ms and 210 ms, respectively.

## Abstract

A self-powered visible-light photodetector was fabricated using a coumarin-derived Schiff base, 4-FMCSB, as the active layer. The compound was synthesized via a two-step process and characterized using FT-IR, NMR, MALDI-TOF-MS, and UV-vis spectroscopy. The optical band gap of 4-FMCSB was determined to be 2.33 eV, with DFT calculations confirming a HOMO–LUMO gap of 2.79 eV. Thin films of 4-FMCSB were deposited on ITO substrates via spin coating, and aluminium contacts were thermally evaporated to form Al/4-FMCSB/ITO photodetectors. The device exhibited a strong rectification ratio, rapid photo response (rise time: 510 ms; fall time: 210 ms), and efficient operation under zero bias. Key performance metrics included a responsivity of 12.6 mA W−1, detectivity of 9.31 × 1010 jones, and a linear dynamic range of 35.94 dB. These findings underscore the potential of coumarin-based Schiff bases in advancing the design of next-generation, energy-efficient optoelectronic devices.

A self-powered visible-light photodetector was fabricated using a coumarin-derived Schiff base, 4-FMCSB, as the active layer.