Alkoxyphenyl-thiophene, -selenophene and -furan substituted benzodithiophene based 2D π-conjugated polymers for polymer solar cells and effect of chalcogen on optoelectronic properties

- New series of 2D π-conjugated polymers (P1-P3) were synthesized by varying chalcogen in donor unit.
- Notable changes were observed in optoelectronic properties with respect to the chalcogen.
- Voc follows VFB evaluated from the Mott-Schottky analysis, leading to positive effect on Jsc and FF.

In order to analyze the correlation between the optoelectronic properties and chalcogen present in the conjugated side chain of benzodithiophene (BDT) based 2D π-conjugated polymers, we synthesized a new series of 2D π-conjugated polymers P1 (S), P2 (Se), and P3 (O), in which alkoxyphenyl-thiophene, alkoxyphenyl-selenophene and alkoxyphenyl-furan substituted BDT as an electron rich donor unit and thieno[3,4-c]pyrrole-4,6-dione as an electron deficient acceptor unit, respectively. The P1-P3 showed varied optoelectronic properties with respect to the chalcogen present in the conjugated side chains of donor unit. The bulk heterojunction (BHJ) polymer solar cells (PSCs) based on P1-P3 showed maximum power conversion efficiency of 3.37, 3.53 and 1.54%, respectively. In particular, open-circuit voltages (Voc) of P1-P3 based PSCs were (0.92, 0.96 and 0.80 V) significantly affected upon chalcogen exchange, which was further analyzed by Mott-Schottky analysis and, the obtained flat-band potential values are well matched with the Voc of P1-P3 based devices.

The correlation between the optoelectronic properties and chalcogen in conjugated side chain of benzodithiophene based 2D π-conjugated polymers (P1-P3) has been investigated. Significant changes were observed in optoelectronic properties of P1-P3 with respect to the chalcogen present in the donor unit. Especially the Voc of P1-P3 based devices substantially altered with respect to the chalcogen in the conjugated side chain.129