Near-infrared organic photodetectors (NIR OPDs) have attracted considerable attention because of their inherent advantages such as a tailorable light absorption property, low-cost fabrication, compatibility with flexible substrates, and room-temperature operation. In particular, the development of NIR detection between 900 and 950 nm is crucial for noise-free communication in ambient environments. In this work, we demonstrate high-detectivity NIR OPDs at 900–950 nm by employing a non-fullerene acceptor (ITIC) used with an NIR-absorbing conjugated polymer (PNIR) for bulk heterojunction (BHJ), which significantly suppressed dark current. Systemic characterizations including electrical, structural, and morphological analyses revealed that ITIC effectively reduces charge recombination during the operation of the OPDs under NIR illumination, resulting in a dark current reduction and high detectivity of over 3.2 × 1011 Jones at 900–950 nm. The results presented here demonstrate that utilizing a non-fullerene acceptor for BHJ-type NIR OPDs is evidently a strategic approach for the simultaneous achievement of the low dark current and high-detectivity of NIR OPDs.

Herein, a strategic approach to enhance the sensitivity of ammonia gas detection using organic semiconductors by boosting the efficiency of ammonia gas-induced stable radical anion formation (SRAF) is reported. This is achieved through rational molecular design and engineering of field-effect transistors (FETs). New rylene diimide derivatives are designed and used to prepare molecular templates for efficient SRAF in thin films, and they are applied as gas-adsorbing active layers in FETs. Substituting linear-shaped perfluoroalkyl (PF) groups to π-electron-deficient naphthalene diimide (NDI) backbone enhances the ammonia gas detection limit to 200 ppb, attributed to the strong electron-withdrawing capability and low steric hindrance of PF groups. Replacing the core backbone (NDI) with perylene diimide (PDI) while retaining the PF group further enhances gasresponsivity up to 18.17 (1700% increase in current) due to the enlarged π-conjugated bridge area. Computational characterization further supports that high electron affinity of the PDI-PF molecules and a larger gas-adsorption area in the PDI core result in the exceptional ammonia gas sensitivity. In addition, beneficial molecular orientation and nanopore formation of PDI-PF facilitate gas adsorption, resulting in remarkably enhanced gas-responsivity. The results indicate that molecular engineering for high-efficiency SRAF suggests a new strategy for developing highsensitivity ammonia sensing platforms.

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Near‐infrared organic photodetectors (NIR OPDs) comprising ultra‐narrow bandgap non‐fullerene acceptors (NFA, over 1000 nm) typically exhibit high dark current density under applied reverse bias. Therefore, suppression of dark current density is crucial to achieve high‐performance of such NIR OPDs. Herein, cyano (CN) with a strong electron‐withdrawing property is introduced into alkoxy thiophene as a π‐bridge to adjust its optoelectronic characteristics, and the correlation between dark current density and charge injection barrier is investigated. Compared with their motivated NFA (COTH), the novel CN‐substituted NFAs, COTCN and COTCN2, exhibited deeper‐lying highest occupied molecular orbital energy levels and narrower optical bandgap (<1.10 eV), owing to the strong inductive and resonance effect of CN. The dark current and total noise currents are minimized as the number of substituted CN increases because of the larger hole injection barrier. Consequently, PTB7‐Th:COTCN2 exhibited the best shot‐noise limited detectivity (D*sh, 1.18 × 1012 Jones) and total noise detectivity (D*n, 1.33 × 1011 Jones) compared with those of PTB7‐Th:COTH (D*sh, 2.47 × 1011 Jones and D*n, 1.96 × 1010 Jones).

A side-chain engineered conjugated polymer provides outstanding NIR detectivity exceeding 2.0 × 10¹²Jones, due to enhanced photo-responsivity and suppressed dark current.