Study of the absorption coefficient of graphene-polymer composites

Abstract

In this work, we have prepared a series of polydimethylsiloxane (PDMS) composites containing various graphene flakes loadings (0.02-2 wt%), and their broadband optical properties are being investigated. We demonstrate the tunability and evolution of transmittance and reflection spectra of the composites in a wide spectral range (0.4-200 μm) as a function of graphene content. Using these data we derive the broadband wavelength-dependent absorption coefficient (α) values. Our results show that α is roughly constant in the visible and IR ranges, and, surprisingly, is approximately one order of magnitude lower in the terahertz regime, suggesting different terahertz radiation scattering mechanism in our composite. Our material could be useful for applications in optical communication, sensing or ultrafast photonics.

Figure 1

(a) Comparison of composites with different graphene loading. (b) Picture demonstrating the flexibility of produced composite. (c) SEM image of cross-section of the composite showing graphene flakes immersed in polymer matrix. (d) Raman spectra of pristine PDMS (lower curve) and graphene/PDMS composite (1 wt% graphene). The D, G and 2D bands characteristic for graphene material are highlighted.

Figure 2

(a) Transmittance, (b) reflectance and (c) absorption spectra of graphene-PDMS composite samples (400 to 1700 nm range), together with PDMS characteristic drops marked with arrows. The % values correspond to graphene concentration, REF stands for pristine PDMS and 2% being the highest graphene concentration. The PDMS signatures disappear for samples with higher graphene loading due to increased absorption of the composite.

Figure 3

Transmittance spectra of graphene-PDMS composite in the wide spectral range (1400 nm–200 µm).

Figure 4

(a) Normalized transmittance as a function of graphene loading together with Beer-Lambert model (solid lines) plotted for three ranges. (b) Calculated absorption coefficient in respect to the wavelength (and frequency) in three spectral ranges compared with literature data for similar materials^,–.