1. Significant power losses caused by the presence of a shunt resistance, RSH, are typically due to manufacturing defects, rather than poor solar cell design. Low shunt resistance causes power losses in solar cells by providing an alternate current path for the light-generated current.
2. Resistance in parallel to the solar cell. Reduces the efficiency of the solar cell and should ideally be as large as possible.
Parallel resistance, electric resistance with parallel interconnection
http://pveducation.org/pvcdrom/shunt-resistance (1.); http://www.photovoltaik.co.at/lexikon/p/parallelwiderstand/ (2.)
Author: Frithjof Kühnert