A New Terthiophene-Thienopyrrolodione Copolymer-Based Bulk Heterojunction Solar Cell with High Open-Circuit Voltage

A new semiconducting polymer based on terthiophene‐thienopyrrolodione alternating building blocks with a deep HOMO energy level (5.66 eV) is presented. The polymer is prepared by a direct heteroarylation polycondensation reaction, which is a low‐cost and green alternative to the standard Stille coupling reaction and thus avoids any use of toxic stannyl derivatives. Integrating the polymer into bulk heterojunction solar cells with [6,6]‐phenyl C71‐butyric acid methyl ester ([70]PCBM) leads to a PCE of over 6% and a high open‐circuit voltage of up to 0.94 V. To obtain these results a unique processing additive, 1‐chloronaphthalene, is used, and a relatively low concentration of [70]PCBM is used in the blend solution. A new terthiophene‐thienopyrrolodione alternating copolymer with a deep HOMO energy level (5.66 eV) is presented. Integrating the polymer into bulk heterojunction solar cells with [6,6]‐phenyl C71‐butyric acid methyl ester ([70]PCBM) leads to an efficiency of over 6% and a high open‐circuit voltage of up to 0.94 V, utilizing 1‐chloronaphthalene as a processing additive and a relatively low concentration of [70]PCBM in the blend solution.