Investigation of the optoelectronic properties of a novel polypyrrole-multi-well carbon nanotubes/titanium oxide/aluminum oxide/p-silicon heterojunction

Abstract The novel design of gold/polypyrrole-multi-walled carbon nanotubes/titanium dioxide/aluminum oxide/P-type silicon/aluminum (Au/PPy-MWCNTs/TiO 2 /Al 2 O 3 /p-Si/Al) is utilized to fabricate supercapacitors, sensors, diodes, and microelectronic devices. The electrical characteristics of the structure are examined both in the dark and under illumination to evaluate its photosensing performance. The real part of the AC conductivity at all voltages and temperatures is observed to be low at low- and mid-frequencies but significantly increases at high frequencies. The imaginary part of the AC conductivity exhibits three distinct behaviors: it is positive at low frequencies and shows both negative and positive values at high frequencies. At specific temperatures, such as 293, 273, and 253 K, the imaginary component of the AC conductivity ( σ acʺ ) is negative only at high frequencies. In the Cole–Cole diagrams, the symmetrical semicircles increase with temperature for all voltages, except at V = −2 V. The real part of the electric modulus ( M ′) shows positive and negative values; however, at certain temperatures, it is positive. The imaginary part of the modulus ( M″ ) is consistently positive.