Advancement and current scenario of engineering and design in transparent supercapacitors: electrodes and electrolyte

Smart devices such as smartphones, smart watches, smart glasses, and transparent control circuits have captured most of the electronics market worldwide. The various smart applications and supporting accessories need an energy storage system with high energy density, highly efficient and transparent energy in nature. Transparent conducting supercapacitors (TCSs) are the most anticipated energy storage system for all such applications. The electrode and electrolyte are the key components of TCSs, which are solely responsible for delivering high energy density and high performance at load. In this regard, in the present review, the basic principle, requirement, and the performance parameters of TCSs are discussed in detail. In addition, comprehensive analysis has been given on recent advances in different materials such as carbon-based material, graphene, metal oxides, and conducting polymers and their composites used as electrodes for TCSs. The focus of this review is concerned with the major difficulties arising in fabrication of transparent electrodes for TCSs. In concern with the electrode and electrolyte, we critically discussed the different methods for enhancing the electrochemical performance and energy density of TCSs. Finally, we have highlighted the few shortcomings and future scope of the TCSs for current energy storage systems.