Effect of layer thickness on the thermoelectric properties of fully sprayed poly(3-hexylthiophene-2,5-diyl) thin films doped with chloroauric acid

Abstract The thermoelectric properties of fully sprayed thin films of poly(3-hexylthiophen-2,5-diyl) (P3HT) doped with chloroauric acid are investigated for different film thicknesses. The film thickness increases logarithmically with increasing amount of deposited material on the surfaces. Both the electrical conductivity and measured Seebeck coefficients of the doped thin films show an optimal polymer layer thickness between 275 and 310 nm and yield a maximum power factor of $$(1.77\,\pm \,0.22) \frac{\mu \text {W}}{\text {m}\cdot \text {K}^2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mrow> <mml:mo>(</mml:mo> <mml:mn>1.77</mml:mn> <mml:mspace/> <mml:mo>±</mml:mo> <mml:mspace/> <mml:mn>0.22</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> <mml:mfrac> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mtext>W</mml:mtext> </mml:mrow> <mml:mrow> <mml:mtext>m</mml:mtext> <mml:mo>·</mml:mo> <mml:msup> <mml:mtext>K</mml:mtext> <mml:mn>2</mml:mn> </mml:msup> </mml:mrow> </mml:mfrac> </mml:mrow> </mml:math> . The optimum layer thickness results from the optimal amount of dopant molecules per monomer between 1.1 and 1.3 at these ratios of P3HT and HAuCl $$_4$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>4</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> for the thin film fabrication.