New insights into the impact of graphene oxide incorporation on molecular ordering and photophysical properties of PTB7:
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New insights into the impact of graphene oxide incorporation on molecular ordering and photophysical properties of PTB7:C70 blends Nidhi Sharma1, Saral K. Gupta1, and Chandra Mohan Singh Negi2,* 1 2
Department of Physics, Banasthali Vidyapith, Rajasthan 304022, India Department of Electronics, Banasthali Vidyapith, Rajasthan 304022, India
Received: 12 August 2020
ABSTRACT
Accepted: 20 October 2020
Nano-fillers have been successfully incorporated in the active layer to enhance the performance of bulk heterojunction (BHJ)-based organic solar cells (OSCs). However, only little information is available on their impact on the molecular ordering of polymers in the BHJ blends. Here, we comprehensively analyze the absorption, photoluminescence (PL), and Raman spectra to understand the effect of incorporation of the graphene oxide (GO) nano-filler in PTB7:C70 blends on the molecular ordering of PTB7 polymer. Absorption spectroscopy unveils how the interplay between interchain and intrachain coupling modifies the molecular order and backbone characteristic of PTB7. The addition of C70 weakens both intrachain and interchain interaction of PTB7. Whereas, intrachain interaction gradually rises with increasing the GO concentration. PTB7 films show weakly interacting J-aggregate behavior; nevertheless, the interaction strength gradually improves with the increasing GO content. The PL analysis indicates well-segregated phase domains and enhanced molecular ordering for composite films with 1 wt% GO. The Raman spectra of PTB7:C70:GO composite films suggests the formation of highly ordered PTB7 aggregates. An in-depth understanding of how these properties of polymer blends change with the GO concentration has significant implications on exploiting them towards the development of electronic devices.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
1 Introduction Conjugate polymers (CPs) have been emerging as the impressive active materials for the variety of electronic devices, including solar cells, photodetectors
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https://doi.org/10.1007/s10854-020-04728-2
and field-effect transistors [1, 2]. Their benefits including cost-effective manufacturing, mechanical flexibility, lightweight, and easier processing have made them materials of scientific and technological interest in recent years, particularly organic materials based solar cells have been envisaged as cost-
J Mater Sci: Mater Electron
effective, lightweight alternatives to silicon-based solar cells [3–6]. In the process of converting the solar power into the electric current, when an organic device is excited by the sunlight, absorption of photons knock out the photo-generated excitons i.e. electron-hole pairs bounded by the Coulombic forces, unlike in inorganic semiconductors where free electrons and holes are generated. In order to generate the photocurrent, these excitons must be dissociated into the free electrons and holes before they vanish due to very limited diffusion length * 10–
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