Solution processed bulk heterojunction organic solar cells using small organic semiconducting materials based on fluorene core unit

Abstract This paper illustrates the synthesis of a new donor-π-donor (D-π-D) type fluorene and hexyl-bithiophene units based chromophore, named as 5′,5‴-(9,9-dioctyl-9-H-fluorene-2-7-diyl)bis (5-hexyl-2,2′-bithiophene) (9RFL) via simple Suzuki coupling reaction. The synthesized 9RFL chromophore was applied as donor for solution-processed bulk-heterojunction (BHJ)-organic solar cells (OSCs). 9RFL chromophore showed the acceptable electrochemical behavior with estimated HOMO and LUMO energy levels of −5.43 eV and −3.50 eV, respectively. A reasonable power conversion efficiency (PCE) of ∼2.13% along with high short circuit current density (J SC ) of ∼9.91 mA/cm 2 , and open circuit voltage (V OC ) of ∼0.718 V were attained by the fabricated BHJ-OSCs with the configuration of ITO/PEDOT:PSS/9RFL:PC 61 BM (1:3, w/w ratio)/Au.