Towards Optimization of Highly Efficient Bulk-Heterojunction Polymer Solar Cells

Interdisciplinary School of Green EnergyThe organics photovoltaics approaches do not rely on conventional single p-n junctions for their function but are based rather upon charge separation at a donor-acceptor interface. Accounts that follow the complexity of the matters facing scientists and engineers involved in organic photovoltaics research and development. The various optical and electronic processes that ultimately produce the transformation of sunlight into electricity are linked in such a way that their respective optimizations require opposing criteria to be fulfilled. In this thesis, the optimization of the polymer solar cells based on regioregular poly(3-hexylthiophene) (P3HT) and the bisadduct of phenyl C61-butyric acid methyl ester (bisPCBM) is studied thoroughly as a role of solvent annealing effect as well as different concentration of bisPCBM. In the case of P3HT:bisPCBM of 1 : 0.8 w/w, more balanced electron mobility and hole mobility are observed, resulting in better performance of the solar cells. Under the best balance conditions such as P3HT:bisPCBM of 1 : 0.8 w/w, the solvent annealing is employed to further clarify the optimization of the devices. Such a treatment leads to the formation of crystalline P3HT domains in the blend films, which is determined by X-ray diffraction, UV-vis spectroscopy, and atomic force microscopy. From this experiment, one can conclude that the best power conversion efficiency of 3.75% is achieved in a layered structure of P3HT:bisPCBM of 1 : 0.8 w/w for a solvent annealing time of 24 h.ope