Molecular orientation and ultrafast charge transfer dynamics studies on the P3HT:PCBM blend

Full text: Ultrathin films of poly(3-hexylthiophene) (P3HT) blended with 6,6.-phenyl-C61-butyric acid methyl ester (PCBM) were investigated by X-ray Absorption Spectroscopy (XAS) and resonant Auger spectroscopy (RAS) in the context of the core-hole approach at the sulfur K absorption edge [1]. P3HT:PCBM blend is a well-known system widely used as a bulk heterojunction (BHJ) photoactive layer in organic photovoltaic (OPV). Its morphology, phase separation and ordering of the constituent phases have been proven to significantly affect the performance of the resulting OPV devices. Herein, thermally annealed P3HT:PCBM films at optimum conditions, in terms of power conversion efficiency (PCE) of the resulting fully-printed OPV modules (2.22% for 8 cm² active area modules), have been proven to be well-ordered films as revealed by the XAS spectra measured at different angles of the incoming photons. Moreover, electron delocalization times were calculated as a function of the excitation energy, resulting in a very low delocalization time in the femtosecond regime. (author)