Characterization of tandem organic solar cells

The tandem solar cell approach is a promising concept for organic photovoltaics (OPVs). However, efficiency determination or, in general, electrical characterization of multi-junction solar cells is challenging. We performed a literature survey of publications reporting tandem OPV characterizations over the period January 2009 to September 2014 and came to the alarming conclusion that 96% of the published efficiencies were not measured according to the relevant standards (Table 1). Even most of the publications claiming to report record efficiencies characterize their devices insufficiently or even incorrectly. The main reason for this malpractice is probably that researchers lack access to adequate experimental equipment for correctly determining spectral mismatches. The absence of matched reference cells for OPVs makes this even more challenging. Some authors treating tandem organic solar cells exactly like single solar cells even appear to be unaware of the existing standards for measuring tandem solar cells.