Since solar energy generation is getting more and more important worldwide PV systems and solar parks are becoming larger consisting of an increasing number of solar panels being serially interconnected. As a consequence panels are frequently exposed to high relative potentials towards ground causing High Voltage Stress (HVS). The effect of HVS on long term stability of solar panels depending on the leakage current between solar cells and ground has been first addressed by NREL in 2005 [1]. This potential degradation mechanism is not monitored by the typical PV tests listed in IEG 61215 [2]. Depending on the technology different types of Potential Induced Degradation (PIO) occur. This paper is focusing on PIO of wafer based standard p-type silicon technology aiming on increasing life times for solar panels once exposed to external potentials in the field. A test setup is presented for simulation of the PIO in the lab and the influence of cell properties on PIO is demonstrated in order to reveal the cell being the precondition for the PIO. However, PIO can also be stopped or minimized on panel and system level as shown in the paper.

In the lifetime of a solar panel, efficiency is degrading continually because panel components are ageing during outdoor exposure (OE). This degradation is mainly due to humidity, temperature, system bias effects and solar irradiation. The solar cell itself may be suffering different degradation mechanisms like light, temperature and potential induced degradation (LID, TID and PID [1]). The focus of this paper is the initial degradation of solar cells within the first hours of operation, which is generally associated with LID. In this work, differences in degradation mechanism for multi and mono cells are investigated for cells and panels based on p-type crystalline silicon. The quality of silicon material is essential as shown in a material comparison. Low and high base resistivities are investigated and different silicon purities ranging from standard feedstock material of different qualities to material based on upgraded metallurgical (UMG) silicon are compared. Interestingly no clear difference between the LID of industrial multiand mono-crystalline cells was found. However, UMG cells show a higher degradation rate partly due to a mechanism identified as temperature induced degradation (TID) that occurs in parallel to LID.

The PV market is still expanding causing the situation in PV industry becoming more and more complex. Different cell types emerge on the market provided by a growing number of cell suppliers. Due to silicon shortage in the past solar cells were getting significantly thinner within the past few years. All these parameters have a potential impact on the mechanical stability of a solar panel. This paper focuses on the dependency of the mechanical stability of solar cells within a solar panel on different factors as cell thickness, cell interconnection technology and cell supplier. Test procedures concerning the mechanical stability of solar panels were carried out according to industry standards and beyond. For detailed evaluation of the panels suitable analysis methods as IV curves and electroluminescence images were utilized. Beside other observations discussed in this paper it has been found that the mechanical stability of solar cells within a solar panel is significantly reduced with decreasing cell thickness. Referring to this result the rapid thickness reduction on wafer level going on in PV industry needs to be investigated closely. Solar cell processes and the module manufacturing need to be adapted.