Polaron Formation in Conducting Polymers: A Novel Approach to Designing Materials with a Larger NLO Response.

Autor: Ahsin A; Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.; School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China., Ejaz I; Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, Abbottabad KPK, 22060, Pakistan., Sarfaraz S; Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, Abbottabad KPK, 22060, Pakistan., Ayub K; Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, Abbottabad KPK, 22060, Pakistan., Ma H; Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Jazyk: angličtina
Zdroj: ACS omega [ACS Omega] 2024 Mar 18; Vol. 9 (12), pp. 14043-14053. Date of Electronic Publication: 2024 Mar 18 (Print Publication: 2024).
DOI: 10.1021/acsomega.3c09468
Abstrakt: Substantial efforts have been made to design and investigate new approaches for high-performance nonlinear optical (NLO) materials. Herein, we report polaron formation in conducting polymers as a new approach to designing materials with a large NLO response. A comparative study of polypyrrole and polypyrrole-based polaron (nPy + where n = 1, 3, 5, 7, and 9) is carried out for optoelectronic and NLO properties. The studied polarons (PPy + ) show excellent electronic properties and have reduced ionization potential (IP) as compared to neutral PPy, and a monotonic decrease is observed with increased chain lengths ( 1Py to 9Py ). Interesting trends of global reactivity descriptors can be seen; the softness (S) increases with an increase in the chain length of PPy, while the hardness (η) decreases in the same fashion. The E H-L gaps for the PPy + polaronic state are significantly lower than their corresponding neutral PPy. In the polaronic model (PPy + ), radicals decisively reduce the crucial excitation energy, reminiscent of excess electrons (alkali metals). The performed TDOS spectral analysis further justifies the better conductive and electronic properties of polarons (PPy + ) with increased chain lengths (conjugation). The static hyperpolarizability response (β o ) is recorded up to 1.3 × 10 2 au for 9Py , while for polaron 9Py + , it has increased up to 3.2 × 10 4 au. The static hyperpolarizability of the 9Py + polaronic state is 246 times higher than that of the corresponding neutral analogue, 9Py . It is observed that the values of β o obtained at the CAM-B3LYP/6-311+G(d,p) level of theory are comparable to those obtained at the LC-BLYP and ωB97XD functionals. The β vec values show a strong correlation with the total hyperpolarizability ( β o ) . Furthermore, the calculated second harmonic generation (SHG) values are up to 4.0 × 10 6 au at 532 nm, whereas electro-optic Pockel's effect (EOPE) is much more pronounced at the smaller dispersion frequency (1064 nm). The TD-DFT study reveal the red-shifted absorption maxima (λ max ) with an increased length of PPy + . A significant reduction in excitation energy (Δ E ) is observed with increased length of PPy and PPy + , which also favors the improved NLO response. Hence, the studied thermally conducting polypyrrole-based polarons (PPy + ) are new entries into NLO materials with better electrical and optical features.
Competing Interests: The authors declare no competing financial interest.
(© 2024 The Authors. Published by American Chemical Society.)
Databáze: MEDLINE
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