Benzo[1, 2-b: 4, 5-b']dithiophene-based copolymers as panchromatic light sensors in organic photodiodes application

Herein, we report a study on the performance of two well-known benzo [1,2-b:4,5-b']dithiophene (BDT) based donor-acceptor (D-A) copolymers for organic photodiode (OPD) application. Judicious material design motif via side-chain and acceptor unit alteration in both polymers resulted in the donor moieties namely, PBDTS-TDZ and PBDB-T, which were applied as active layers with fullerene derivative PC₆₁BM in a bulk heterojunction OPD. Panchromatic light detection was afforded despite the molecular and structural changes in both polymers. Inverted OPD based on PBDB-T: PC₆₁BM showed a comparatively broader photoresponse and better performance, with specific detectivity [EQE] of 3.749 × 10¹² [62%] at a bias voltage of 2 V under red light illumination. This work entrenches the inter-dependent relationship existing between polymer structural design and their device performance for organic photodiode (OPD) application.