Tuning of nonlinear optical bistability tuned by fullerene concentration in polyaniline-fullerene (PANI-C60) hybrid organic films
Third-order nonlinear optical (NLO) parameters, NLO absorption coefficient (β), imaginary part of susceptibility (χi(3)), saturation intensity and figure of merit of polyaniline–fullerene (PANI-C60) films were investigated using open-aperture z-scan measurement with a 532 nm Nd:YAG laser. Switching...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2025-01-01
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| Series: | Next Nanotechnology |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2949829525001056 |
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| Summary: | Third-order nonlinear optical (NLO) parameters, NLO absorption coefficient (β), imaginary part of susceptibility (χi(3)), saturation intensity and figure of merit of polyaniline–fullerene (PANI-C60) films were investigated using open-aperture z-scan measurement with a 532 nm Nd:YAG laser. Switching of saturable absorption (SA) to reverse saturable absorption (RSA) behaviour (NLO bistability) was observed in these organic hybrid films by changing the concentration of C60 in the PANI matrix. It is attributed to the charge transfer complex (CTC) formation between PANI and C60 in the film. PANI and low C₆₀-doped films exhibited SA, indicative of ground-state bleaching, while higher C₆₀ loadings triggered a switch to RSA due to enhanced excited-state absorption facilitated by efficient intersystem crossing induced by CTC formation. A transition from SA to RSA was confirmed from the observed sign reversal in β and χi(3). Values of β and χi(3), were shifted from –59.80 cm/GW to 99.3 cm/GW and –0.52 × 10−10 esu to 0.96 × 10−10 esu, respectively, in PANI and PANI-C₆₀. Films were prepared via the drop-casting technique with varying C₆₀ concentrations. SEM analysis showed morphological changes from uniform domains of PANI to C60-rich agglomerates. The CTC formation is confirmed by the FTIR and UV–visible absorption spectroscopy. The bandgap reduction from 2.62 eV in the PANI film to 2.20 eV at the highest C₆₀ concentration, with an increase in Urbach energy from 0.40 eV to 0.95 eV, indicated enhanced disorder and localised states. To the best of our knowledge, this is the first report of a concentration-driven SA-to-RSA transition in PANI–C₆₀ solid films, establishing their potential in photonic applications. |
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| ISSN: | 2949-8295 |