Enhanced sub-1 eV detection in organic photodetectors through tuning polymer energetics and microstructure

Abstract

One of the key challenges facing organic photodiodes (OPDs) is increasing the detection into the infrared region. Organic semiconductor polymers provide a platform for tuning the bandgap and optoelectronic response to go beyond the traditional 1000-nanometer benchmark. In this work, we present a near-infrared (NIR) polymer with absorption up to 1500 nanometers. The polymer-based OPD delivers a high specific detectivity D * of 1.03 × 10 10 Jones (−2 volts) at 1200 nanometers and a dark current J d of just 2.3 × 10 −6 ampere per square centimeter at −2 volts. We demonstrate a strong improvement of all OPD metrics in the NIR region compared to previously reported NIR OPD due to the enhanced crystallinity and optimized energy alignment, which leads to reduced charge recombination. The high D * value in the 1100-to-1300-nanometer region is particularly promising for biosensing applications. We demonstrate the OPD as a pulse oximeter under NIR illumination, delivering heart rate and blood oxygen saturation readings in real time without signal amplification.

An A–D–A′–D–A-Type Narrow Bandgap Electron Acceptor Based on Selenophene-Flanked Diketopyrrolopyrrole for Sensitive Near-Infrared Photodetection

“…Organic photodetectors (OPDs) with specific responses in the near-infrared (NIR) region offer unique potential for applications such as remote control of intelligent and portable electronic devices, night surveillance, biomedical monitoring, and image sensing. − However, the limited availability of molecular materials suitable for NIR-OPDs poses a challenge, as superior narrow bandgap organic semiconductors are required to ensure efficient charge generation and NIR response. − Historically, significant efforts have been made in the development of p-type polymer donors with NIR light absorption for NIR-OPDs due to the limited tunability of fullerene acceptors in chemical structures. ,, However, the emergence of nonfullerene acceptors (NFAs) in recent years has revolutionized the field of NIR organic semiconductors due to the fact that NFAs can offer tunable optical bandgaps, energy levels, and molecular crystallinity. ,− In 2015, Zhan et al reported the development of ITIC, an donor–acceptor–acceptor (A–D–A) type fused-ring electron acceptor with absorption onset approaching 800 nm . This accomplishment marks a significant milestone in the advancement of narrow bandgap organic semiconductors.…”

A tetrathienopyrrole-based ladder-type donor polymer for high-performance organic near-infrared cavity detectors

“…12 Many different NIR-absorbing organic small molecule and polymer compounds have been prepared and some of these have been proven to be useful for NIR organic photodetectors (OPDs) in a wavelength range inaccessible for silicon. 13–19 However, for each targeted wavelength (range), new molecules have to be developed, which is a very time consuming and costly process.…”

Bias Dependence of Organic-Oxide Phototransistors with Peak Infrared Absorption at 1550 nm

“…There are ongoing efforts to develop alternative semiconductors − that facilitate low-cost, monolithic detector fabrication. Among these emerging technologies, organic semiconductors such as donor–acceptor conjugated polymers − enable facile and scalable processing and functionality to infrared wavelengths beyond 1 μm. However, according to the energy-gap law, as the bandgap of organic semiconductors decreases, the recombination rate of photogenerated excitons increases, leading to a decline in device efficiency at longer wavelengths.…”