Bulk heterojunction organic photovoltaic devices based on low band gap small molecule BTD-TNP and perylene–anthracene diimide

Bulk heterojunction (BHJ) photovoltaic devices were fabricated from the blends of compounds BTD-TNP (electron donor) and P–A (electron acceptor) and characterized through current–voltage measurements under illumination. Compound BTD-TNP contains dithyenyl-benzothiadiazole central unit and cyanovinylene-p-nitrophenyl terminal moieties. Compound P–A is a symmetrical perylene–anthracene diimide with tert-butylphenoxy side groups at the 1,7-bay positions. Both the absorption spectra and the incident photon to the current conversion efficiency (IPCE) spectra of the device were extended up to 800 nm. A power conversion efficiency of 2.85% with short-circuit current density of 6.8 mA/cm2, open-circuit voltage of 0.88 V and fill factor of 0.47 were obtained. It was found that the hole and electron mobility in the active layer were about 4.6×10−5 and 8.8×10−4 cm2/Vs, respectively, which indicates the fairly balanced charge transport in the device.