Organic Solar Cells with Nanofibers in the Active Layer Obtained by Coaxial Electrospinning

Abstract

The high demand for energy and the intensification of climate change have led to the need to improve renewable energy sources, such as solar energy. Organic bulk heterojunction (BHJ) cells using conjugated polymers as the electron donor in the active layer are an alternative because they are easy processability, flexible, have the absorption spectrum corresponding to the structure of the polymer, and can be synthesized in an endless variety of chemical structures. One of the limiting factors for large-scale applications was the relatively low conversion of solar energy into electricity, but this has been practically overcome recently, as efficiencies of around 20% have been achieved for small-area devices and around 16% for larger devices, approaching conventional silicon cells. The device’s stability remains the most restraining factor, as it has to last at least ten years in sun and weather exposure. This review presents works that improve the efficiency of photovoltaic devices by addressing the development of materials used in the active layer (semiconductor polymers and acceptor materials). Additionally, the use of nanofibers in the active layer obtained by the electrospinning technique is discussed. The nanofiber quality parameters (solute properties, solution properties, processing conditions, and environmental conditions) are discussed, including coaxial electrospinning.