Efficient conventional- and inverted-type photovoltaic cells using a planar alternating polythiophene copolymer

Wonho Lee, Hyosung Choi, Sungu Hwang, Jin Young Kim, Han Young Woo

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

A low-band-gap alternating copolymer, poly{5,6-bis(octyloxy)-4-(thiophen-2- yl)benzo[c]-1,2,5-thiadiazole} (PTBT), was synthesized and investigated for photovoltaic applications. PTBT showed a minimized torsion angle in its main backbone owing to the introduction of solubilizing octyloxy groups on the electron-poor benzothiadiazole unit, thereby resulting in pronounced intermolecular ordering and a deep level of the HOMO (-5.41 eV). By blending PTBT with [6,6]phenyl-C61-butyric acid methyl ester (PC 61BM), highly promising performance was achieved with power-conversion efficiencies (PCEs) of 5.9 and 5.3% for the conventional and inverted devices, respectively, under air mass 1.5 global (AM 1.5G, 100 mWcm -2) illumination. The open-circuit voltage (V OC≈0.85-0.87 V) is one of the highest values reported thus far for thiophene-based polymers (e.g., poly(3-hexylthiophene) V OC≈0.6 V). The inverted device also achieved a remarkable PCE compared to other devices based on low-band-gap polymers. Ideal film morphology with bicontinuous percolation pathways was expected from the atomic force microscopy (AFM) images, space-charge-limited current (SCLC) mobility, and selected-area electron-diffraction (SAED) measurements. This molecular design strategy is useful for achieving simple, processable, and planar donor-acceptor (D-A)-type low-band-gap polymers with a deep HOMO for applications in photovoltaic cells. A hard cell: A planar low-band-gap copolymer (PTBT) with high intermolecular ordering and a deep HOMO level was synthesized for use in photovoltaic cells. PTBT contained alternating thiophene and alkoxy-substituted benzothiadiazole groups. Both conventional- and inverted-type photovoltaic devices showed promising power-conversion efficiencies (5.9 and 5.3%, respectively).

Original languageEnglish
Pages (from-to)2551-2558
Number of pages8
JournalChemistry - A European Journal
Volume18
Issue number9
DOIs
Publication statusPublished - 2012 Feb 27
Externally publishedYes

Fingerprint

Photovoltaic cells
Energy gap
Copolymers
Conversion efficiency
Thiophenes
Equipment and Supplies
Polymers
Thiophene
Electrons
Thiadiazoles
Butyric acid
Atomic Force Microscopy
Open circuit voltage
Lighting
Electric space charge
Electron diffraction
Torsional stress
Atomic force microscopy
Esters
Air

Keywords

  • charge transfer
  • copolymerization
  • pi interactions
  • polymers
  • solar cells

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

Cite this

Efficient conventional- and inverted-type photovoltaic cells using a planar alternating polythiophene copolymer. / Lee, Wonho; Choi, Hyosung; Hwang, Sungu; Kim, Jin Young; Woo, Han Young.

In: Chemistry - A European Journal, Vol. 18, No. 9, 27.02.2012, p. 2551-2558.

Research output: Contribution to journalArticle

Lee, Wonho ; Choi, Hyosung ; Hwang, Sungu ; Kim, Jin Young ; Woo, Han Young. / Efficient conventional- and inverted-type photovoltaic cells using a planar alternating polythiophene copolymer. In: Chemistry - A European Journal. 2012 ; Vol. 18, No. 9. pp. 2551-2558.
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abstract = "A low-band-gap alternating copolymer, poly{5,6-bis(octyloxy)-4-(thiophen-2- yl)benzo[c]-1,2,5-thiadiazole} (PTBT), was synthesized and investigated for photovoltaic applications. PTBT showed a minimized torsion angle in its main backbone owing to the introduction of solubilizing octyloxy groups on the electron-poor benzothiadiazole unit, thereby resulting in pronounced intermolecular ordering and a deep level of the HOMO (-5.41 eV). By blending PTBT with [6,6]phenyl-C61-butyric acid methyl ester (PC 61BM), highly promising performance was achieved with power-conversion efficiencies (PCEs) of 5.9 and 5.3{\%} for the conventional and inverted devices, respectively, under air mass 1.5 global (AM 1.5G, 100 mWcm -2) illumination. The open-circuit voltage (V OC≈0.85-0.87 V) is one of the highest values reported thus far for thiophene-based polymers (e.g., poly(3-hexylthiophene) V OC≈0.6 V). The inverted device also achieved a remarkable PCE compared to other devices based on low-band-gap polymers. Ideal film morphology with bicontinuous percolation pathways was expected from the atomic force microscopy (AFM) images, space-charge-limited current (SCLC) mobility, and selected-area electron-diffraction (SAED) measurements. This molecular design strategy is useful for achieving simple, processable, and planar donor-acceptor (D-A)-type low-band-gap polymers with a deep HOMO for applications in photovoltaic cells. A hard cell: A planar low-band-gap copolymer (PTBT) with high intermolecular ordering and a deep HOMO level was synthesized for use in photovoltaic cells. PTBT contained alternating thiophene and alkoxy-substituted benzothiadiazole groups. Both conventional- and inverted-type photovoltaic devices showed promising power-conversion efficiencies (5.9 and 5.3{\%}, respectively).",
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AU - Woo, Han Young

PY - 2012/2/27

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