Efficient spirobifluorene-core electron-donor material for application in solution-processed organic solar cells

Abstract

Efficient spirobifluorene-based organic small molecule (RTh-Sp-CF3) was synthesized in a simple manner via Suzuki coupling reaction containing an alkyl bithiophene as donor and 3,5-bis (trifluoromethyl) benzene as acceptor unit. The spirobifluorene-based small molecule was utilized as an electron-donor materials with well-known electron-acceptor material, phenyl-C61-butyric acid methyl ester (PC61BM) in the solution-processed small molecule organic solar cells (SMOSCs). The incorporation of 3,5-bis (trifluoromethyl) benzene unit as electron-acceptor has significantly tuned the energy levels of small molecule and obtained the HOMO and LUMO energy levels of −5.35eV and −3.92eV, respectively. SMOSCs fabricated with RTh-Sp-CF3 accomplished an overall power conversion efficiency (PCE) of ∼2.12% with short circuit current (JSC) of ∼8.42mA/cm2 and the open-circuit voltage (VOC) of ∼0.66V. The reasonable JSC and VOC of devices might be attributed to the presence of strong electron-withdrawing fluorine units in RTh-Sp-CF3, which resulted from the improved absorption and electrochemical properties.