Synthesis and photovoltaic properties of a small molecule acceptor with thienylenevinylene thiophene as π bridge

A new n-type organic semiconductor (n-OS) acceptor with (E)-5-(2-(5-(2-ethylhexyl)thiophen-2-yl)vinyl)-thiophene-2-yl (TVT) functional group as π-bridge to link indacenodithiophene (IDT) core and 3-(dicyanomethylidene)indan-1-one (IC) terminals, named ITVT, was synthesized and applied in polymer solar cells (PSCs). It is the first time employing TVT unit in n-OS small molecule acceptor. Benefited from the conjugated TVT side groups, the small molecule ITVT shows a strong absorption at the short wavelength range (300–500 nm). In addition, ITVT exhibits a low optical band gap (E_g ^opt) of 1.48 eV and a medium electron mobility of 1.85 × 10⁻⁴ cm² V^-1 s^-1. A wide band gap polymer PBZ was chosen as donor to fabricate an inverted BHJ PSCs because of the complementary absorption and matched molecular energy levels. The as-cast PSCs yield a power conversion efficiency (PCE) of 5.84% with an open-circuit voltage (V_oc) of 0.96 V and a short-circuit current density (J_sc) of 14.22 mA cm⁻² under the illumination of AM 1.5 G at 100 mW cm⁻².