Investigation of the Role of Silicon in Donor Moiety in D‐π‐A Type Conjugated Polymers With Selenophene Bridges for Solar Cell Applications

ABSTRACT In this study, the influence of silicon incorporation into donor moieties of donor–acceptor (D–A) type conjugated polymers with selenophene π‐bridges for organic solar cell (OSC) applications was investigated. Two novel polymers, P1 and P2 , were synthesized, with 4,4‐dioctyl‐4H‐silolo[3,2‐b:4,5‐b’] dithiophene ( P1 ) and 2,2′‐bithiophene ( P2 ) used as donor units, while 2,1,3‐benzooxadiazole (BOz) was employed as the electron‐accepting unit. Optical and electrochemical analyses were conducted, revealing that the silole donor unit in P1 resulted in enhanced π‐conjugation, a lower HOMO–LUMO bandgap (1.56 eV vs. 1.64 eV for P2 ), and improved intermolecular charge transport properties. Superior performance was demonstrated by P1 ‐based devices, with a PCE of 3.64%, a J SC of 8.60 mA/cm 2 , a V OC of 0.66 V, and a FF of 64.04%. Improved molecular planarity and π – π stacking in P1 , attributed to the silicon‐containing donor, were found to contribute to enhanced charge carrier mobility and reduced structural disorder in the active layer. The inclusion of selenophene as a π ‐bridge was also observed to improve intermolecular interactions and optical absorption. It is concluded that silicon incorporation plays a crucial role in tuning the optoelectronic and photovoltaic properties of conjugated polymers, underscoring its potential for advancing the design of next‐generation OSC materials and devices for renewable energy applications.