Design and computational analysis of DPP-based A-D-A’-D-A small-molecule acceptors for near-infrared photodetectors

Near-infrared photodetectors (OPDs) have witnessed rapid development due to their wide-ranging applications in biometric monitoring, sports sensing, and other emerging fields. However, the limitations of inorganic semiconductors, such as high cost and complex fabrication processes, have spurred the urgent exploration of high-performance organic small-molecule electron acceptors. This study presents the design and computational investigation of diketopyrrolopyrrole (DPP)-based A-D-A’-D-A type small-molecule electron acceptors for near-infrared (NIR) photodetectors (OPDs). Using first-principles calculations with Materials Studio, the molecular geometry, surface electrostatic potential (ESP), and frontier orbital energy levels (HOMO/LUMO) were systematically analyzed. The results show that the designed molecules exhibit narrow bandgaps (0.75-1.02 eV), corresponding to NIR absorption wavelengths of 1,214-1,652 nm. Alkylation modification of the DPP core suppresses its electron-donating ability, while tuning side-chain electron-donating groups enables precise modulation of the molecular bandgap and electron-withdrawing capacity. Compared with traditional CPDT-based acceptors, the DPP-based materials demonstrate stronger electron-withdrawing characteristics and enhanced potential for NIR light absorption. This work provides a theoretical framework for developing solution-processable, mechanically flexible organic acceptors, addressing the limitations of inorganic semiconductors (e.g., high cost, complex fabrication) in wearable medical and flexible electronic devices. The proposed design strategy offers a scalable approach for optimizing optoelectronic properties in NIR OPDs, facilitating their application in biometric monitoring and sports sensing scenarios.