**4. Conclusions**

Polymer solar cells carry various advantages, which are suitable to flexible and fiber-shaped solar cells. However, optimum thickness for photovoltaic coatings and adequate smoothness for the surface of each layer (substrate, photoactive layer and electrodes) are required to obtain higher power conversion efficiencies and to prevent the short-circuiting in the conventional and flexible devices. Suitable coating techniques and materials for developing photovoltaic effect on flexible polymer based textile fibers are also needed not to damage photovoltaic fiber formation in continuous or discontinuous process stages. Many studies still continue for improving stability and efficiency of photovoltaic devices.

Flexible solar cells can expand the applications of photovoltaics into different areas such as textiles, membranes and so on. Photovoltaic fibers can form different textile structures and also can be embedded into fabrics forming many architectural formations for powering portable electronic devices in remote areas. However, optimal photovoltaic fiber architecture and the suitable manufacturing processes to produce it are still in development stage. More studies are required to design and perform for a working photovoltaic fiber.

A viable photovoltaic fiber that is efficient and have resistance to traditional textile manufacturing processes, which are formed from some consecutive dry and wet applications, and, which damage to textile structure, will open new application fields to concepts of smart textiles and smart fabrics.
