The output of photovoltaic modules is specified in accordance with DIN EN 61215 under standard test conditions (1000 W/m², 25 °C, AM1.5). Only the radiation intensity on the front of the module is defined. Determining the module output by the sum of the individual outputs of the front and rear sides of the module is not suitable, as the irradiation on the rear side of the module is generally much lower. There are no standards for the evaluation of bifacial solar modules with a transparent rear side.

Other open issues that are of interest to the industry relate to ageing and degradation behaviour. Due to the modified module design (no full-surface contacting of the back of the solar cell, transparent backside encapsulation), there is still no reliable data on ageing behaviour. Degradation phenomena such as voltage-induced degradation (PID) also pose challenges for this module technology. While the PID effect in standard solar cells only affects the front side of the solar cell, in bifacial solar cells this effect also occurs on the rear side of the solar cell.

The aim of this research group is to develop theoretical models for the evaluation and standards for the characterisation of bifacial photovoltaic cells and modules. Bifacial solar modules utilise both the light incident on the front and the back of the module. As the front and rear sides are irradiated differently and the area under consideration is doubled, questions inevitably arise with regard to hot-spot behaviour with inhomogeneous irradiation. With regard to the stability of the modules, ageing aspects must also be taken into account for the rear side of the module. The development of methods for realistic energy rating with reference to module service life enables optimisation potential to be incorporated into the development, design and manufacturing process of bifacial solar modules. On the other hand, the methods developed enable optimised system design and efficient operation of PV systems.