Novel alkoxyanthracene donor and benzothiadiazole acceptor for organic thin film transistor and bulk heterojunction organic photovoltaic cells

Novel alkoxy anthracene (ODA)-based polymeric semiconductors were designed for polymer solar cell applications. Alkoxyanthracene, which contains many π electrons and electron donating group, was easily synthesized. The copolymers, poly(alkoxy anthracene-alt-thiophene benzothiadiazole thiophene) poly(ODA-TBT) and poly(alkoxy anthracene-alt-benzothiadiazole) poly(ODA-BT), have been obtained by Suzuki coupling polymerization. Both polymers have ODA unit as a donor and benzothiadiazole as an acceptor. ODA-TBT has thiophene linkages between ODA and benzothiadiazole. The optical, thermal, and electrochemical properties have been investigated by UV-visible absorption, thermal gravimetric analysis, differential scanning calorimetry, and CV. Organic thin-film transistor using polymers showed that the hole mobility of poly(ODA-alt-TBT) was around 3.6 × 10^-3 cm²/Vs with on/off ratio of 9.91 × 10⁵ while that of poly(ODA-alt-BT) was around 1.21 × 10^-2 cm²/Vs with on/off ratio of 2.64 × 10 ⁶. Organic photovoltaic performance based on polymers were evaluated with a configuration of ITO/PEDOT:PSS/active layer/LiF/Al. Poly(ODA-TBT) exhibits a short circuit current (J_sc) of 3.9 mA/cm² and power conversion efficiency (PCE) of 1.4%, and poly(ODA-BT) exhibits the J _sc of 6.4 mA/cm² and PCE of 2.2%. The better device performance of poly(ODA-BT) is attributed to its charge transfer ability and enhanced mobility and crystallinity although poly(ODA-BT) does not have extended π-conjugation due to twisted structure compared with poly(ODA-TBT).