Unveiling the effect of side chains and fluorination on the photovoltaic performance of D-A copolymers: a comparative study of P-HBT-T, P-FBT-T and P-FBT-O

Yilmaz E. A., Cevher S. C., Cevher D., Hizalan G., ÇIRPAN A.

Materials Today Energy, cilt.36, 2023 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 36
  • Basım Tarihi: 2023
  • Doi Numarası: 10.1016/j.mtener.2023.101369
  • Dergi Adı: Materials Today Energy
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, INSPEC
  • Anahtar Kelimeler: Benzodithiophene, Conjugated polymer, Organic solar cells, Thienopyrroledione
  • Orta Doğu Teknik Üniversitesi Adresli: Evet

Özet

Three random D-A copolymers containing thienopyrroledione (TPD) and benzodithiophene (BDT) named P-HBT-T, P-FBT-T, and P-FBT-O were synthesized. The effects of side chains on BDT and fluorination to benzothiadiazole on the photovoltaic performances of fabricated solar cells were investigated. The highest occupied molecular orbital (HOMO) levels of the polymers were −5.57, −5.51, and −5.65 eV for P-HBT-T, P-FBT-T, and P-FBT-O, respectively, suggesting low-lying HOMO energy levels. The optimized weight ratios of the polymer to PC71BM were determined as 1:2 with 24 mg/mL blend concentration for all polymers, and the maximum power conversion efficiencies (PCEs) of the devices were 7.35%, 7.76%, and 9.21% for P-HBT-T, P-FBT-T, and P-FBT-O, respectively, after optimizations with 1,8-diiodooctane (DIO) and 1-chloronaphthalene (CN). Trap-assisted recombination and bimolecular recombination loss mechanisms, which are PCE limiting mechanisms, were examined for all devices. The morphological and topographical properties were investigated using transmission electron microscopy (TEM) and atomic force microscopy (AFM), respectively. Our findings demonstrate that P-FBT-O-bearing organic solar cells (OSCs) emerged as the best-performing device due to their deeper HOMO level, high molecular weight, lower trap-assisted and bimolecular recombination, and superior morphology.