Starting from the question, what fast electronic transport is based on, and why organic materials in general are more problematic in this respect than typical inorganic ones, methods are introduced that allow to measure the principal material property charge carrier mobility. Some representative experimental results are presented which prove that mobilities around 1–10 cm2/V s can be achieved at room temperature, and more than 100 cm2/V s at low temperature—but only if chemical purity and structural order can be brought to a very high level.

No abstract

No abstract

t g a r t , D 70550 S t u t t g a r t , Germany AbstractOrganic photovoltaic thin film s t r u c t u r e s made by vacuum vapor deposition have been studied. From t h e spectral response as a function of t h e absorption coefficient we conclude t h a t electron -hole generation takes place a t t h e interface between t h e organic thin film and one or b o t h of t h e semitransparent cover electrodes. The observed s h o r t circuit currents, however, are t o o large to be explained on t h e basis of a direct light-induced charge transfer at t h e organic thin film/ electrode interface. Rather, a contribution of t h e bulk-absorbed photons is necessary t o account f o r the observed quantum yield. Transfer of t h e energy t o t h e interface sites can be explained by diffusional migration of excitons. The efficiency of charge separation can be improved by combining donor a n d acceptor type partners in organic double layers. The efficiency of power conversion, however, n o t only depends on a suitable choice of t h e absorption spectra and of t h e ionic energy levels of t h e materials employed, b u t also on t h e internal cell resistance, a f a c t t h a t calls f o r high charge carrier mobilities, and hence f o r using materials with crystal structures t h a t allow s t r o n g n-electron interactions, and f o r deposition in high chemical purity and s t r u c t u r a l perfection.

No abstract