Polymer solar cells have many intrinsic advantages, such as their light weight, flexibility, and low material and manufacturing costs. Recently, polymer tandem solar cells have attracted significant attention due to their potential to achieve higher performance than single cells. Photovoltaic's deal with the conversion of sunlight into electrical energy. Classic photovoltaic solar cells based on inorganic semiconductors have developed considerably [1] since the first realization of a silicon solar cell in 1954 by Chapin, Fuller and Pearson in the Bell labs. [2] Today silicon is still the leading technology on the world market of photovoltaic solar cells, with power conversion efficiencies approaching 15 – 20% for mono-crystalline devices. Though the solar energy industry is heavily subsidized throughout many years, the prices of silicon solar cell based power plants or panels are still not competitive with other conventional combustion techniques – except for several niche products. An approach for lowering the manufacturing costs of solar cells is to use organic materials that can be processed under less demanding conditions. Organic photovoltaic's has been developed for more than 30 years, however, within the last decade the research field gained considerable in momentum [3,4]. The amount of solar energy lighting up Earth's land mass every year is nearly 3,000 times the total amount of annual human energy use. But to compete with energy from fossil fuels, photovoltaic devices must convert sunlight to electricity with a certain measure of efficiency. For polymer-based organic photovoltaic cells, which are far less expensive to manufacture than silicon-based solar cells, scientists have long believed that the key to high efficiencies rests in the purity of the polymer/organic cell's two domains -- acceptor and donor.

organic solar cells, solar energy, photovoltaic, polymer