Emerging solar cells, which are driven mainly by their benefits to the environment and sustainable features of using renewable resources, have focused on the use of bio-based starting materials. Bio-based polyurethane (PU) polymer electrolyte has good potential to be applied in emerging solar cells, as it is versatile, flexible, and safe, and it requires non-intricate preparation. PU has a unique multiphase structure composed of flexible and rigid segments of polymer chains. This provides physical stability, flexibility in maintaining a wide range of electrochemical stability, and the ability to hold pressure between anodes and cathodes. All of these features permit the assembly of PU polymer electrolytes in solar cells. In addition, the flexible segment of polyols can serve as polymeric solvent to dissociate anions and cations from metal salts by forming intermolecular interactions with electron pairs in oxygen and/or nitrogen atoms and providing active sites for ionic transport to facilitate a redox process in dye solar cells (DSCs). Although the bio-based PU described has a good potential to be used as a polymer electrolyte for DSCs, the progress is limited to a few works reported in this chapter. A lot more effort must be made to successfully apply these emerging materials in DSCs, especially on the scale-up level and field testing. © 2023 American Chemical Society.