ABSTRACT
This chapter completes the analysis of the operation of solar cells by describing the mechanisms of charge collection, composed of the combination of carrier transport, recombination, and extraction at the selective contacts. In a solar cell under intense photogeneration, there occurs a competition of transport and recombination that determines whether the carriers generated at an internal point will reach the external contacts, which is a necessary condition for the efficient operation of the device under sunlight. The chapter establishes the main intuitive ideas concerning the charge collection by either diffusion, or by drift in strong electrical fields associated with space-charge regions. It outlines a basic classification of the main operation modes for charge collection, depending on the size of the depletion region with respect to the thickness of the absorber. The chapter concludes with some practical considerations for the measurement and reporting of solar cell performance.
