<p>Transition metal oxides (TMOs) have demonstrated exceptional electrochemical performance and outstanding conductivity recently, indicating their potential as a cathode in hybrid supercapacitors. Therefore, the current study highlights the simple synthetic method of regulated nickel oxide and cobalt doping nickel oxide thin film fabrication over the conducting plate using successive ionic layer adsorption and reaction (SILAR). Consequently, at 1 mA cm⁻² current density, an optimal Co-doped NiO (Co:NiO 3) thin film electrode demonstrates the maximum specific capacitance (specific capacity) 1309 F g⁻¹ (720 C g⁻¹). Additionally, at 1 mA cm⁻² current density, the manufactured flexible hybrid all-solid-state supercapacitor device (Co:NiO 3//PVA-KOH//rGO) demonstrated 135 F g⁻¹ specific capacitance, and at a specific power (SP) of 1.77 kW kg⁻¹, the device had a maximum specific energy (SE) of 48 Wh kg⁻¹. After successful 5000 GCD cycles, the FHSSC devices demonstrate capacitive retention and coulombic efficiency of approximately 84% and 103%, respectively. Also, the built device was charged for 30 s and used for 80 s to power lighting 50 LEDs to demonstrate its practicality. A new era of widespread integration of device-grade applications could be ushered in by the developed device.</p>