Toward a comprehensive understanding of molecular doping organic semiconductors (review)

Molecular electrical doping of organic semiconductors has emerged as a valuable strategy to improve the performance of organic (opto-)electronic devices and to extend the range of achievable functionality. In the present review, a brief overview of typical applications employing molecular electrical doping is given, followed by a critical summary of experiments performed to elucidate the microscopic mechanisms involved. In providing an in-depth discussion of the models that have been established on the basis of these experiments, a comprehensive portray of the current state of affairs emerges, which allows deriving certain guidelines for the design of improved molecular dopants. At the same time, phenomenological differences in the effect of doping in different classes of organic semiconductors are identified. This precludes, at the moment, a unifying explanation of all underlying processes, but nevertheless serves to steer future research efforts.