Ion irradiation induced modifications of P3HT: A donor material for organic photovoltaic devices. (January 2017)

• Record Type: Journal Article
• Authors: Sharma, T.; Singhal, R.; Vishnoi, R.; Lakshmi, G.B.V.S.; Chand, S.; Avasthi, D.K.; Kanjilal, A.; Biswas, S.K.
• Is Part Of: Vacuum. Volume 135(2017)
• Page Start: 73
• Page End: 85
• Publication Date: 2017-01
• Subjects: Poly(3-hexylthiophene) -- Raman spectroscopy -- UV- visible absorption spectroscopy -- Conductivity; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2016.10.027
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: The modifications of Poly(3-Hexylthiophene) (P3HT) thin films have been investigated by irradiating with 90 MeV Ni 7+ ions at different fluences (1 × 10 9 to 1 × 10 11 ions/cm 2 ). Thin films have been characterized by micro-Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), UV-visible absorption Spectroscopy, Photoluminescence spectroscopy (PL), Atomic Force Microscopy (AFM) and small angle X-ray scattering (SAXS) analysis. The narrow FWHM of C=C mode and the larger intensity ratio of C-C and C=C modes are identified at low fluences. The IR active modes with increased intensity indicates the increased conjugation length, while the XRD analysis revels the improved crystallinity with enhanced molecular ordering. The XPS analysis shows that chemical bonding nature near the film surface is not affected by irradiation. The room temperature electrical conductivity is found to be increased from 2.48 × 10 −6 to 1.35 × 10 −5 Ω −1 cm −1 at the fluence of 1 × 10 10 ions/cm 2 . The temperature dependence of dc conductivity has been explained using Mott's variable range hopping model. SAXS detector images confirm the presence of ion tracks and density variation between the track core and halo regions. It is found that less intense heating effect in the halo region of ion path could induce the molecular ordering of P3HT. Highlights: Poly(3-hexylthiophene) (P3HT) thin films are spin casted with thickness ∼ 300 nm. Thin films are irradiated at different fluences from 1 × 10 9 ions/cm 2 to 1 × 10 11 ions/cm 2 by 90 MeV Ni +7 ion beam. The molecular ordering of P3HT is explained in terms of less heating effects in the halo region surrounding the incident ion path. The increased conductivity has been observed due to increased conjugation length and molecular ordering. Variation in the absorption and emission spectra due to energetic ions is also investigated.