What is it about?
In this paper, we present a design strategy for red-light selective organic photodiodes (OPDs) by combining optical and material tuning. Specifically, we explore approaches to make OPDs that respond preferentially to red wavelengths (i.e. narrowband in the red part of the spectrum) without relying on external filters. We investigate how intrinsic absorption, exciton activation, and layer engineering can be leveraged to tailor the photoresponse. The result is an OPD whose sensitivity is shifted and confined into the red region, while maintaining good performance metrics (responsivity, detectivity, dynamic range).
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Why is it important?
Targeted spectral detection: Many applications (e.g., biomedical sensing, implantable sensors, optical communication, imaging) require detectors that are sensitive to a specific narrow band (such as red or near-infrared) rather than a broadband response. A red-selective OPD reduces background noise and enhances signal specificity. Filterless operation/device simplicity: By embedding spectral selectivity into the material and optical design, the need for external optical filters (which add bulk, cost, and complexity) is eliminated or minimized. Organic/flexible platform: Organic photodiodes offer advantages such as mechanical flexibility, lightweight, potentially lower cost, and compatibility with integration on nonrigid substrates or implantable devices. Achieving narrow spectral selectivity while maintaining strong responsivity, high detectivity, and a wide dynamic range is nontrivial. Our work demonstrates that, with proper tuning, these trade-offs can be effectively balanced.
Perspectives
This study opens several interesting directions and potential impacts: 1) Extension to other spectral bands: The design principles can be generalized to create OPDs selective to other wavelengths (e.g. near-infrared, deep red) by choosing and tuning materials appropriately. 2) Integration into miniaturized sensor systems: Red-selective OPDs could be integrated into compact, wearable or implantable sensor platforms for biomedical monitoring (e.g. pulse oximetry, optical biosensing) or environmental monitoring. 3) High-resolution imaging: Arrays of narrowband OPDs could be used for spectrally resolved imaging or multispectral sensor arrays without bulky color filters. 4) Stability and scalability: Future work may focus on improving the long-term stability, manufacturability, and large-area production of these selective OPDs. 5) Hybrid/complementary devices: Combining red-selective OPDs with complementary detectors (e.g. green, blue) could lead to full-color, filter-free imaging or sensing systems. 6) New materials/architectures: Novel organic semiconductors, exciton management strategies, or optical cavity designs could further enhance selectivity, efficiency, and tunability.
Rabiul Islam
Technische Universitat Dresden
Read the Original
This page is a summary of: Red-light-selective organic photodiodes via optical and material tuning for implantable sensors, September 2025, SPIE,
DOI: 10.1117/12.3076625.
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