Semitransparent fullerene-free polymer solar cell with 44% AVT and 7% efficiency based on a new chlorinated small molecule acceptor

Design and synthesis of low bandgap (LBG) nonfullerene small molecule acceptor (SMA) is of critical importance for realizing high-efficiency semitransparent organic solar cells (ST-OSCs). In this article, we synthesized a LBG new SMA, ID-4Cl, by introducing four chlorine substituents onto the electron-acceptor terminals of IDIC. Its optical bandgap (E-g(opt)) is 1.51 eV, which helps to obtain large short-circuit current-density (J(sc)) without scarifying the transmittance in the visible human-eye-sensitive wavelength region (360-700 nm). The optimal opaque device performance was obtained on a relatively thin active layer of 65 nm, showing high power conversion efficiency (PCE) of 10.2%, large J(sc) of 18 mA/cm(2), high fill factor (FF) of 75%, and open-circuit voltage of 0.77 V. The ST-OSC device fabricated with the structure of ITO/PEDOT:PSS/active layer/PDINO/Au (15 nm) shown a PCE of 6.99% in a small area of 4 mm(2) and 1.1% in a large area of 1 cm(2) with an AVT (average visible transmittance) of 43.7%, showing potentiality in building integrated photovoltaics.