Enhanced Photocurrent Spectral Response in Low‐Bandgap Polyfluorene and C₇₀‐Derivative‐Based Solar Cells

Abstract

Plastic solar cells have been fabricated using a low‐bandgap alternating copolymer of fluorene and a donor–acceptor–donor moiety (APFO‐Green1), blended with 3′‐(3,5‐bis‐trifluoromethylphenyl)‐1′‐(4‐nitrophenyl)pyrazolino[70]fullerene (BTPF70) as electron acceptor. The polymer shows optical absorption in two wavelength ranges, λ < 500 nm and 600 < λ < 1000 nm. The BTPF70 absorbs light at λ < 700 nm. A broad photocurrent spectral response in the wavelength range 300 < λ < 1000 nm is obtained in solar cells. A photocurrent density of 3.4 mA cm–2, open‐circuit voltage of 0.58 V, and power‐conversion efficiency of 0.7 % are achieved under illumination of AM1.5 (1000 W m–2) from a solar simulator. Synthesis of BTPF70 is presented. Photoluminescence quenching and electrochemical studies are used to discuss photoinduced charge transfer.

Polymer‐Fullerene Bulk‐Heterojunction Solar Cells

“…[65,66,[71][72][73] Andersson et al prepared more than 10 different polyfluorene (PF) derivatives called APFO polymers. This class of polymers offers a sufficiently large variability in the position of the HOMO/LUMO levels, and polymers with a low band gap that show a photosensitivity down to 1 mm (polymer 2, Fig.…”

Low-band gap poly(di-2-thienylthienopyrazine):fullerene solar cells

“…Reports on low-band gap polymers are emerging recently. [6][7][8][9][10][11] In designing low-band gap polymers for bulk heterojunctions solar cells various aspects need to be considered. For a conventional p-n junction solar cell with a single band gap ͑E g ͒, a reduction of E g results in an increased absorption of light but decreased open circuit voltage ͑V oc ͒.…”

Carrier generation and transport in bulk heterojunction films processed with 1,8-octanedithiol as a processing additive

“…The quest for higher solar cell efficiencies has therefore focused on smaller band gap polymers designed and synthesized to improve the harvesting of the solar radiation. [5][6][7][8][9][10][11][12] The synthesis of copolymers comprising alternating electron-rich and electron-deficient units has been proven to be a successful route to small band gap semiconducting polymers. Following this synthetic strategy, the small band gap ͑E g Ϸ 1.46 eV͒ copolymer, poly͓2,6-͑4,4-bis-͑2-ethylhexyl͒-4H-cyclopenta ͓2,1-b;3,4-bЈ͔dithiophene͒-alt-4,7-͑2,1,3-benzothiadiazole͔͒ PCPDTBT, was synthesized.…”