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Ultra-Sensitive Short-Wave Infrared Organic Photodetectors Enabled by a π-Conjugation Extended Proquinoid Electron Acceptor

2025-12-31T15:00:00Z

Title: Ultra-Sensitive Short-Wave Infrared Organic Photodetectors Enabled by a π-Conjugation Extended Proquinoid Electron Acceptor Author(s): Choi, Yeonsu; Park, Se Jeong; Oh, Seunghyun; Lee, Un-Hak; Rhee, Seunghyun; Whang, Dong Ryeol; Chung, Sein; Jung, Juhyoung; Cho, Kilwon; Lee, Bo Ram; Yoon, Sung Cheol; Shim, Jae Won; Ko, Seo-Jin Abstract: Short-wavelength infrared (SWIR) light detection technologies have attracted considerable attention due to their broad applications in bioimaging, sensing, and optical communication. Despite this promise, achieving high-performance organic SWIR photodetectors (SWIR OPDs) remains a major challenge due to intrinsically weak photoresponse and sensitivity in this spectral region. Herein, a novel proquinoid-type non-fullerene acceptor (NFA), denoted as TQC-4Cl is reported, which exhibits an ultra-narrow band gap of 1.01 eV and a broad spectral response extending beyond 1200 nm, enabled via an aromatic-quinoid transformation strategy. Thermal annealing of the TQC-4Cl film significantly enhanced crystallinity and molecular ordering. Consequently, the optimized TQC-4Cl-based SWIR OPDs exhibit an exceptionally low dark current density (J d) of 4.38 x 10-8 A cm-2 , noise current of 466 fA (at 4 Hz), and a high external quantum efficiency (EQE) of 13.66% at 1200 nm at -0.5 V bias, resulting in a shot-noise limited specific detectivity (Dsh*) of 1.06 x 1012 Jones and a noise current-based specific detectivity (Dn*) of 2.84 x 1011 Jones under the same bias conditions. The ideal phase-separated morphology and high crystallinity of the photoactive layer provide the beneficial condition enabling efficient charge extraction, suppressed bimolecular recombination, and reduced energetic disorder. Furthermore, the devices demonstrated long-term operational stability at 85 degrees C, underscoring their superior thermal durability. This study not only marks the advancement toward the realization of highly sensitive and thermally robust SWIR OPDs but also contributes to the rational molecular design strategies for ultra-narrow bandgap organic semiconductors for next-generation optoelectronic devices.

Quinoidal Nitrogen-Bridged Terthiophene Acceptors Enabling Broadband Spectral Response Reaching 1.4 μm in SWIR Organic Photodetectors

2025-12-31T15:00:00Z

Title: Quinoidal Nitrogen-Bridged Terthiophene Acceptors Enabling Broadband Spectral Response Reaching 1.4 μm in SWIR Organic Photodetectors Author(s): Alam, Shabaz; Park, Se Jeong; Li, Meng Qiang; Sim, Suhui; Yang, Hye In; Yoon, Ji Hye; Lee, Un-Hak; Chung, Sein; Park, Byeongchan; Cho, Kilwon; Cheon, Young Ghil; Shin, Jin Yong; Rhee, Seunghyun; Eun, Hyeong Ju; Kim, Jong H.; Lee, Bo Ram; Ko, Seo-Jin; Lee, Jaewon Abstract: Organic photodetectors (OPDs) capable of detecting short-wavelength infrared (SWIR) radiation beyond the silicon cutoff (approximate to 1.1 mu m) have attracted significant attention due to their potential applications, such as machine vision, remote sensing, medical imaging, artificial intelligence, etc. However, designing organic materials with high sensitivity in the SWIR range remains challenging. Here, a new series of ultra-narrow bandgap small molecular acceptors, 5MTT-F, 5MCN-F, and 5MCN-Cl, based on a nitrogen-bridged terthiophene core, designed to promote planarity, pi-delocalization, and quinoidal characteristics, is reported. Systematic modulation of pi-bridges and terminal groups enable precise tuning of energy levels and absorption profiles, extending the photoresponse up to approximate to 1400 nm with optical bandgaps as low as 0.85 eV. OPDs fabricated with these acceptors and the donor polymer PCE10-0F exhibit excellent performance, with 5MTT-F device achieving a responsivity of 0.12 AW-1 and a specific detectivity of 1.69 x 1012 Jones at 1.1 mu m. Notably, 5MCN-based OPDs demonstrate broadband SWIR detection with detectivities of 8.98 x 1010 Jones up to 1.3 mu m. This work presents a viable molecular design strategy for achieving efficient SWIR OPDs and deepening the understanding of structure-property-performance relationships in organic semiconductors for broadband infrared detection.

Non-Halogenated Solvent Processed Shortwave Infrared Organic Photodetectors Using Sub-1 eV Bandgap Acceptor with Cyano Substitution

Title: Non-Halogenated Solvent Processed Shortwave Infrared Organic Photodetectors Using Sub-1 eV Bandgap Acceptor with Cyano Substitution Author(s): Luong, Hoang Mai; Ha, Jong-Woon; Wakidi, Hiba; Chae, Sangmin; Yi, Ahra; Mukherjee, Subhrangsu; Do, Sang; Worthington, Vivian; Kim, Brian Minki; Qu, Zhong-Ze; Kim, Hyo Jung; Lee, Un-Hak; Yoon, Sung Cheol; Ade, Harald; Ko, Seo-Jin; Nguyen, Thuc-Quyen Abstract: Shortwave infrared (SWIR) organic photodetectors (OPDs) offer significant potential but face persistent challenges such as limited responsivity and high noise under reverse bias. This work presents the development of high-performance OPDs for SWIR sensing, leveraging a newly designed non-fullerene acceptor (NFA) named 6CN. The 6CN molecule, featuring a fused-cyclopentadithiophene (fCPDT) core and cyano-substituted pi-bridges, exhibits an ultra-narrow optical bandgap of approximate to 0.98 eV, enabling efficient SWIR absorption up to 1250 nm. When blended with the PTB7-Th polymer donor, the resulting bulk-heterojunction (BHJ) demonstrates strong charge transfer, broad spectral coverage, and robust charge transport. Notably, device fabrication employs the environmentally friendly solvent o-xylene without halogenated additives, yielding OPDs with superior photoresponse compared to those processed from conventional chlorinated solvents. The o-xylene processed devices achieve high responsivity (approximate to 0.2 A W-1 at 1200 nm) and specific detectivity exceeding 3 x 1011 Jones across 300-1200 nm, representing a significant advance for eco-friendly, flexible SWIR photodetection technologies.

Visibly Transparent Monolithic Perovskite/Organic Tandem Solar Cells Achieving Over 6% Light-Utilization Efficiency

2026-01-31T15:00:00Z

Title: Visibly Transparent Monolithic Perovskite/Organic Tandem Solar Cells Achieving Over 6% Light-Utilization Efficiency Author(s): Ryu, Jun; Lee, Seojun; Lee, Un-Hak; Choi, Yeonsu; Lee, Tae-Gyeong; Park, Se Jeong; An, Sumin; Rhee, Seunghyun; Lim, Han-Gyun; Bae, Inho; Kim, Jong H.; Lee, Bo Ram; Kim, Gyu Min; Kim, Jincheol; Ko, Seo-Jin; Kang, Dong-Won Abstract: Transparent photovoltaics for solar-window applications must balance human-visible clarity with meaningful power output. Here, we report a selectively absorbing, monolithic perovskite/organic tandem that decouples visible transmittance from photocurrent generation and minimizes voltage loss delivering record light-utilization efficiency (LUE) for visibly transparent (VT) tandem devices. An ultra-wide-bandgap, DMA-alloyed perovskite top sub-cell harvests primarily = 50%, while delivering a record-high open circuit voltage (V-OC) of 2.38 V. These results establish optical-electrical co-design guidelines for high-clarity, power-generating glazing, which explicitly connect materials and interface choices in both sub-cells to energetic disorder, built-in potential, and recombination.