Dicyanovinyl sexithiophene as donor material in organic planar heterojunction solar cells: Morphological, optical, and electrical properties

• Published in: Organic electronics Vol. 12; no. 12; pp. 2243 - 2252
• Main Authors: Levichkova, Marieta, Wynands, David, Levin, Alexandr A., Walzer, Karsten, Hildebrandt, Dirk, Pfeiffer, Martin, Janonis, Vytautas, Pranaitis, Mindaugas, Kažukauskas, Vaidotas, Leo, Karl, Riede, Moritz
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-12-2011; Elsevier
• Subjects: Applied sciences; Compound structure devices; Electronics; Energy; Exact sciences and technology; Hole mobility; Morphology; Natural energy; Oligothiophene; Optoelectronic devices; Organic solar cell; Photovoltaic conversion; Planar heterojunction; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Solar cells. Photoelectrochemical cells; Solar energy; Organic solar cell; Oligothiophene; Morphology; Hole mobility; Planar heterojunction; Atomic force microscopy; Charge carrier mobility; High temperature; Organic solar cells; Oligomer; Thiophene derivatives; Frequency shift; Self organization; Absorption band; Optical properties; Optical characteristic; Activation energy; Electrical characteristic; Heterojunction; X ray diffraction; Solar cell; Solid state; Side chain; Fullerenes; Thiophene polymer; Planar device; Room temperature; Planar technology
• ISSN: 1566-1199; 1878-5530
• DOI: 10.1016/j.orgel.2011.09.022

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► Study of morphology, optical and electrical properties of vacuum deposited DCV6T-Bu films. ► Improved self-organization in the solid state on room temperature substrate. ► Enhanced crystalline growth on substrate at elevated temperature during deposition. ► No increase of the DCV6T-Bu hole mobility upon substrate heating. ► Increased photocurrent in planar heterojunctions with C60 when DCV6T-Bu is grown on heated substrate.
We study the morphology and optical properties of vacuum deposited films of the α-ω-bis-(dicyanovinylen)-sexithiophene, comprising four butyl side chains DCV6T-Bu(1,2,5,6) (DCV6T-Bu). An absorption band showing vibronic substructure indicates ordered molecular arrangement in the solid state. The room temperature (RT) self-organization is confirmed by X-ray diffraction (XRD). For films grown on heated substrates, XRD analysis and atomic force microscopy display increased crystallinity with larger domain size. In correlation to the XRD data, with increasing substrate temperature the absorption of the heated films becomes more structured and continuously shifts to longer wavelengths. Further, the hole mobility in DCV6T-Bu/C60 planar heterojunction (PHJ) devices, utilizing DCV6T-Bu films grown at RT and elevated substrate temperature is investigated using the charge extraction by linearly increasing voltage method. The derived values of the activation energy are consistent with the corresponding DCV6T-Bu film morphology. However, the charge carrier mobility does not increase with improving molecular order, as is evident by the obtained mobility values of 1.0
×
10
−6
cm
2/V
s for the RT and 3.1
×
10
−7
cm
2/V
s for the heated device, respectively. Finally, DCV6T-Bu/C60 PHJ solar cells consisting of absorber layers deposited on heated and unheated substrates are compared.