Broadband, low-noise and fast short-wave infrared photodetection enabled by thermally robust all-polymer organic photodetectors

We report the first demonstration of all-polymer organic photodetectors (OPDs) with efficient short-wave infrared (SWIR) detection beyond 1200 nm, surpassing current benchmarks for polymer-based photodetection systems. By using a donor polymer poly[[6,7-bis[5-(2-hexyldecyl)-2-thienyl][1,2,5]thiadiazolo[3,4- g ]quinoxaline-4,9-diyl][2,2′:5′,2”-terthiophene]-5,5”-diyl] (PTTQ(HD)) and pairing it with an acceptor polymer fluorinated poly[[1,2,3,6,7,8-hexahydro-2,7-bis(2-octyldodecyl)-1,3,6,8-dioxobenzo[lmn][3,8]phenanthroline-4,9-diyl][3,3′-bisfluoro-2,2′-bithiophene]-5,5′-diyl] (F-N2200), we achieve favorable energy-level alignment, enhanced exciton dissociation, and superior thermal stability. Compared to the fullerene-based PTTQ: [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC71BM) reference, the PTTQ:F-N2200 devices exhibit extended external quantum efficiency (EQE) response up to 1400 nm, improved responsivity (0.093 A/W at 1200 nm), suppressed dark current density (3.83 × 10 −7 A/cm²), and a detectivity of 1.05 × 10 11 Jones, representing one of the highest values reported for all-polymer systems. Structural analyses via grazing-incidence wide-angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM) reveal thermally induced molecular ordering and stable morphology, correlating with significantly reduced shot noise and improved dynamic response, including a −3 dB bandwidth of 155 kHz and response time below 1.5 μs. Furthermore, deep-level transient spectroscopy (DLTS) and electrochemical impedance spectroscopy (EIS) measurements confirm the reduction of trap states and suppression of non-radiative losses in the all-polymer system. This work sets a new benchmark for all-polymer SWIR photodetectors and underscores their promise in high-speed, low-noise optoelectronics for remote sensing, optical communication, and infrared imaging. • All-polymer OPDs achieve SWIR detection beyond 1200 nm. • PTTQ:F-N2200 shows strong thermal stability. • AFM reveals domain changes after thermal annealing. • Annealing at 200 °C preserves low noise current and enhances responsivity. • Dynamic response compared with non-fullerene devices.