Versatile <scp>aza‐BODIPY</scp> ‐based <scp>low‐bandgap</scp> conjugated small molecule for light harvesting and <scp>near‐infrared</scp> photodetection

The versatile nature of organic conjugated materials renders their flawless integration into a diverse family of optoelectronic devices with light-harvesting, photodetection, or light-emitting capabilities. Classes of materials that offer the possibilities of two or more distinct optoelectronic functions are particularly attractive as they enable smart applications while providing the benefits of the ease of fabrication using low-cost processes. Here, we develop a novel, multi-purpose conjugated small molecule by combining boron-azadipyrromethene (aza-BODIPY) as electron acceptor with triphenylamine (TPA) as end-capping donor units. The implemented donor–acceptor–donor (D–A–D) configuration, in the form of TPA-azaBODIPY-TPA, preserves ideal charge transfer characteristics with appropriate excitation energy levels, with the additional ability to be used as either a charge transporting interlayer or light-sensing semiconducting layer in optoelectronic devices. To demonstrate its versatility, we first show that TPA-azaBODIPY-TPA can act as an excellent hole transport layer in methylammonium lead triiodide (MAPbI3)-based perovskite solar cells with measured power conversion efficiencies exceeding 17%, outperforming control solar cells with PEDOT:PSS by nearly 60%. Furthermore, the optical bandgap of 1.49 eV is shown to provide significant photodetection in the wavelength range of up to 800 nm where TPA-azaBODIPY-TPA functions as donor in near-infrared organic photodetectors (OPDs) composed of fullerene derivatives. Overall, the established versatility of TPA-azaBODIPY-TPA, combined with its robust thermal stability as well as excellent solubility and processability, provides a new guide for developing highly efficient multi-purpose electronic materials for the next-generation of smart optoelectronic devices. Ministry of Education (MOE) National Research Foundation (NRF) Published version Lam Yeng Ming would like to thank the support of the Singapore Ministry of Education Academic Research Fund Tier 2 (Grant No. MOE2019-T2-1-085). Annalisa Bruno and Enkhtur thank the National Research Foundation for the financial support (Grant No. S18-1176-SCRP). Prashant Sonar is thankful to QUT for the financial support from the Australian Research Council (ARC) for the Future Fellowship (Grant No. FT130101337) and QUT core funding (Grant No. QUT/322120-0301/07). Ajay K. Pandey acknowledges support from Australia India Strategic Research Fund (Project AISRF53820).