Efficient SWIR Organic Photodetectors with Spectral Detection Extending to 1.4 μm Using a Benzobisthiadiazole-Based Acceptor

Organic photodetectors (OPDs) offer significant advantages in biomedical applications, including medical imaging, heart rate monitoring, and tumor therapy. Despite advancements in OPD technology, the efficiency of these devices in the short-wave infrared (SWIR) region remains considerably lower than that of inorganic semiconductors. To tackle this challenge, this study developed an ultra-narrow bandgap acceptor of CS-1, featuring an A-D-A1-D-A structure where benzobisthiadiazole (BBT) serves as the electron-deficient unit A1, which exhibits a wide absorption range from 300 to 1550 nm. This molecular design not only enhances the absorption properties of the material but also improves the overall performance of the OPD device. It is worth noting that the optimal PTB7-Th:CS-1 device realizes a specific detectivity (Dn*) of 2.96 x 1010 Jones at 1.30 mu m, making it one of the most efficient devices at this wavelength to date. Additionally, it demonstrates the high linear dynamic range (LDR) of 91.9 dB even at 1300 nm. These results indicate that the PTB7-Th:CS-1 device significantly enhances detection efficiency in the SWIR region, surpassing most commercially available silicon-based photodetectors. This highlights the significant potential of the BBT unit for achieving high-performance SWIR OPDs.