Electrochemical capacitors are known for their fast charging and superior energy storage capabilities and have emerged as a key energy storage solution for efficient and sustainable power management. This article comprehensively explores the fundamental principles, architectural advancements, and material innovations underpinning supercapacitor technology. It covers the evolution of supercapacitor performance, the comparison of pseudocapacitors, double‐layer capacitors, electrolytes, and the integration of innovative nanostructured materials, such as carbon nanotubes, transition metal oxides, MXene, and graphene, and it investigates the hybrid systems that bridge the gap between capacitors and batteries. The article also discusses the future perspectives of supercapacitor technology. By examining emerging trends and recent research, this review provides a comprehensive overview of electrochemical capacitors as an emerging energy storage system.

Owing to its low resistivity, high transmittance, and tunable optical band gap, ZnO is of great interest for optoelectronic applications. Herein, the sol–gel technique was used to synthesize un-doped and zirconium-doped zinc oxide (ZZO) nanostructures with different concentrations of Zirconium (Zr). X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy, and photoluminescence (PL) measurements were used to investigate the influence of Zr doping on the structural, optical, and electrical properties of developed nanostructures. XRD and SEM confirmed the increase in crystallite size with increasing concentrations of Zr. Raman analysis indicated the presence of oxygen vacancies in synthesized nanostructures. UV-Vis spectroscopy illustrated the blue shift of band gap and red shift of the absorption edge for ZZO nanostructures with increasing concentrations of Zr. For the measurement of electrical properties, the spin-coating technique was used to deposit un-doped and Zr-doped ZnO layers of ~165 nm thickness. The four-probe-point (4PP) method illustrated that the doping of Zr caused a reduction in electrical resistance. Hall Effect measurements showed a high value, 3.78 × 10²⁰ cm⁻³, of the carrier concentration and a low value, 10.2 cm²/Vs, of the carrier mobility for the Zr-doped layer. The high optical transmittance of ~80%, wide band gap of 3.51 eV, low electrical resistivity of 1.35 × 10⁻³ Ω·cm, and maximum carrier concentration of 3.78 × 10²⁰ cm⁻³ make ZZO nanostructures one of the most promising candidates for the application of transparent conductive oxide (TCO) in optoelectronic devices.