Asymmetric push-pull small molecules with auxiliary electron-accepting unit for bulk heterojunction organic solar cells

摘要： Two small molecular donors (TPA-DPP and TPA-DPP-MDN) were designed with asymmetric push-pull structure, namely, donor-acceptor (D-A) and donor-acceptor-acceptor (D-A-A) systems. They were synthesized and investigated by thermogravimetric analysis, UV–vis spectra, X-ray di?raction, density functional theory (DFT) calculation, electrochemical and the photovoltaic (PV) measurement. The D-A-A architecture (TPA-DPP-MDN) exhibited lower highest occupied molecular orbital (HOMO) of –5.18 eV, narrower optical band gap of 1.52 eV, better thermal stability and higher degree of ordered aggregation than these of the D-A system (TPA-DPP). TPA-DPP-MDN based PV device showed better performance with higher open-circuit voltage (VOC) and short-circuit current density (JSC) than these of TPA-DPP based PV devices due to the low-lying HOMO level and wide spectral absorption range of TPA-DPP-MDN.