The evolution and emergence of organic solar cells and hybrid organic-silicon heterojunction solar cells have been deemed as promising sustainable future technologies, owing to the use of π-conjugated polymers. In this regard, the scope of this review article presents a comprehensive summary of the applications of π-conjugated polymers as hole transporting layers (HTLs) or emitters in both organic solar cells and organic-silicon hybrid heterojunction solar cells. The different techniques used to synthesize these polymers are discussed in detail, including their electronic band structure and doping mechanisms. The general architecture and principle of operating heterojunction solar cells is addressed. In both discussed solar cell types, incorporation of π-conjugated polymers as HTLs have seen a dramatic increase in efficiencies attained by these devices, owing to the high transmittance in the visible to near-infrared region, reduced carrier recombination, high conductivity, and high hole mobilities possessed by the p-type polymeric materials. However, these cells suffer from long-term stability due to photo-oxidation and parasitic absorptions at the anode interface that results in total degradation of the polymeric p-type materials. Although great progress has been seen in the incorporation of conjugated polymers in the various solar cell types, there is still a long way to go for cells incorporating polymeric materials to realize commercialization and large-scale industrial production due to the shortcomings in the stability of the polymers. This review therefore discusses the progress in using polymeric materials as HTLs in organic solar cells and hybrid organic-silicon heterojunction solar cells with the intention to provide insight on the quest of producing highly efficient but less expensive solar cells.

Water pollution by organic dyes continues to pose a serious health and environmental threat to the ecosystem. Although adsorption using biopolymer-based hydrogels has proven to be an ideal technique for the treatment of these dye contaminants from aqueous solutions, these hydrogels suffer from lack of mechanical stability and recovery as compared to synthetic polymers. Herein, we review the low-cost synthesis of hydrogel incorporated with inorganic components mainly focusing on strategies to improve the mechanical stability and separation of the hydrogel in removing methylene blue (MB) dye from aqueous solution. The literature shows that hydrogel nanocomposites are a class of materials that have flourished significant consideration, especially concerning water treatment. In adsorption technology, hydrogel nanocomposites act as absorbents, prominent to enhance their removal efficiency towards contaminants. This review highlights the preparation and use of hydrogel nanocomposites as efficient adsorbents. In-depth discussions on adsorption and diverse synthetic routes of hydrogels have been devoted to applications of these nanocomposites and are compared in this contribution to the removal efficiency of MB dye from wastewater.