Wavelength‐Selective Organic Photodetectors

Abstract

Spectroscopic sensing combined with optical imaging is crucial with respect to today's ever‐growing demand for instant analytical techniques to be incorporated in various handheld and wearable devices. Further miniaturization and integration of such types of sensors is critical and wavelength‐selective organic photodetectors (OPDs) may provide the required technology. In this progress report, some early OPD applications and their potential are presented. Crucial device parameters such as the specific detectivity, external quantum efficiency, and dark current density of visible and near‐infrared wavelength‐selective photodetectors are compared and assayed to theoretical and semi‐empirical limits. The different organic detector approaches include the use of inherently narrow‐band absorbers as well as internally filtered and microcavity devices. Each of these strategies comes with its own specific material and device design criteria, around which material development and selection should be centered to move beyond the current state of the art. As OPD technology matures, device stability becomes important and is hence also briefly discussed. Via this perspective, it is aimed to provide the reader with critical insights into the device physics and chemistry of wavelength‐selective OPDs, hereby providing leverage for new ideas to bring this technology to the market.

Tuning Electronic and Morphological Properties for High‐Performance Wavelength‐Selective Organic Near‐Infrared Cavity Photodetectors

“…[ 11 ] For applications requiring narrow‐band detection, several strategies have been proposed, including the use of narrow‐band absorbers, [ 12 ] charge collection narrowing, [ 13 ] and resonant microcavity device architectures. [ 14 ] The latter is especially promising since such devices are electronically thin, yet optically thick at the resonance wavelength, [ 15,16 ] which is simply determined by the total thickness of the photoactive film and the transport layers sandwiched between the (semi)reflecting electrodes constituting the microcavity. [ 14 ]…”

Ultraviolet Narrowband Photomultiplication Type Organic Photodetectors with Fabry−Pérot Resonator Architecture

“…Organic photodetectors (OPDs) have aroused broad interests in recent years owing to their tunable spectral response, compatibility with flexible devices, solution, and room temperature processability. [ 1–5 ] OPDs can be classified as photodiode type OPDs (PD‐OPDs) with external quantum efficiency (EQE) <100% and photomultiplication type OPDs (PM‐OPDs) with EQE >100% according to their working mechanism. [ 6,7 ] In light of the bandwidth of photoresponse, the OPDs can be divided into broadband and narrowband OPDs.…”

Photomultiplication‐Type Organic Photodetectors for Near‐Infrared Sensing with High and Bias‐Independent Specific Detectivity

“…Organic photodetectors (OPDs) are a promising optical detection technology due to the adjustable optical, electronic and mechanic properties of organic semiconductors. [ 1 , 2 , 3 ] Thanks to advances in material science and device engineering, extensive investigations, especially in terms of dark current, enabled the rapid development of OPDs, nowadays offering comparable performance to silicon (Si) photodiodes in many parameters. [ 4 , 5 , 6 ] Photovoltaic‐type OPDs (PV‐OPDs) typically possess moderate photoresponse, and a zero bias working condition is often needed for optimal performance, demanding more advanced and expensive readout circuits.…”