Organic Narrowband Photodetector with a Filter Electrode Using Fabry–Pérot Cavities for Enhanced Performance

Abstract

Photodetectors (PDs) with wavelength-selective capabilities are crucial for various applications. However, traditional narrowband photodetectors (NPDs), which rely on external optical filters, hinder device miniaturization and integration. Recent filter-free strategies have utilized thick active layer for absorption-based spectral filtering, however, these often compromise the device’s response speed. Moreover, absorption-filtered PDs face performance degradation due to heat accumulation in the active layer under prolonged or intense light exposure. In this work, we present a novel approach for an organic NPD that eliminates the need for external filters by incorporating a Fabry−Pérot resonant cavity as a filter electrode. The filter electrode is constructed using an Ag: Cu thin film, deposited via magnetron sputtering, as the mirror, while an indium tin oxide (ITO) layer serves as the cavity spacer. By fine-tuning the ITO layer’s thickness, transmission peaks can be precisely adjusted across the visible spectrum. To further enhance transmittance, Al₂O₃ and ZnO are incorporated as transmission-enhancing layers, with ZnO also functioning as a hole-blocking layer to reduce dark current. We demonstrate an organic NPD with a transmission peak at 650 nm, achieving a peak responsivity of 0.22 A/W, a specific detectivity of 4.12 × 10¹² Jones, a response time of 26.3 µs, and a linear dynamic range of 108.3 dB. This design offers improved performance compared to traditional absorption-based NPDs, without significantly sacrificing speed or efficiency.