(Invited) Operating Mechanisms of Organic Bulk-Heterojunction Solar Cells
A discussion of impedance analysis in the much less studied case of collection-limited solar cells is discussed. Recent experimental analyses of transport processes are presented. We show how by incorporating blocking electrodes into the cell structure transport mechanisms can be understood in terms of diffusion-recombination models. Impedance spectra reveal carrier diffusion signature when blocking or extracting cathode contacts are employed. Finally contact effects are also addressed. The energy level alignment at the contacts is of primary importance in establishing the contact extracting ability and carrier selectivity. Several characterization techniques of the contact properties are explored.