Publications

Potential-induced degradation (PID) of photovoltaic (PV) modules gets a lot of attention since 2010 when Solon published their findings about a degradation mechanism in their PV modules caused by high potential differences between the solar cell and the grounded frame. Module level efficiency drops of 30% and more caused by PID have been reported. A stress test for PID according to IEC 62804 and a recovery test in the same conditions were conducted on a set of 49 commercially available PV modules. In this paper we report the irreversibility of highly affected (i.e. over 85% PID) PV modules. From this point of view, it is important to detect and recover PID before the point of no return. Furthermore, the impact of PID on the different parameters of a PV module and their relevance in order to detect PID in the field are reported.

Interface quality plays a key role in solar cell applications. Interface recombination at the front and rear surfaces, which determine this quality, have significant effects on open circuit voltage and fill factor values. In this work, several surface treatments were applied on Cu(In,Ga)Se2 (CIGS) surfaces to improve the interface quality. Besides, the passivation layer implementation was investigated to reduce interface recombination between the buffer and absorber layers.

Here, we introduce deep eutectic solvent (DES)–silica composites as a promising candidate for solid composite electrolytes (SCEs). The proposed DES-based gel electrolytes, further referred to as eutectogels (ETGs), are characterized by high ionic conductivity (1.46 mS cm–1), thermal (up to 130 °C), and electrochemical stability (up to 4.8 V) and are chemically inert to solvents and water. These ETGs can be easily processed and potentially at lower costs compared to ionic-liquid-based composite electrolytes. The good prospects of ETGs for application in Li/Li-ion batteries are demonstrated by stable cycling of Li/ETG/LiFePO4 cells over 100 cycles at C/10.

Reducing the absorber layer thickness below 1 mu m for a regular copper indium gallium di-selenide (CIGS) solar cell lowers the minimum quality requirements for the absorber layer due to shorter electron diffusion length. Additionally, it reduces material costs and production time. Yet, having such a thin absorber reduces the cell efficiency significantly. This is due to incomplete light absorption and high Molybdenum/CIGS rear-surface recombination [1]. The aim of this research is to implement some innovative rear surface modifications on a 430 nm thick CIGS absorber layer to reduce both these affects: an aluminium oxide passivation layer to reduce the back-surface recombination and point contact openings using nano-particles for electrical contact. The impact of the implementation of all these rear-surface modifications on the opto-electrical properties of the CIGS solar cell will be discussed and analyzed in this paper.

KF and NaF treatments were done for single-stage co-evaporated CuIn0.7Ga0.3Se2. The absorber layers were grown on a substrate with an alkali barrier layer and NaF was either added before or after absorber layer growth. No differences were found on the device performance amongst the procedures to add Na. This is expected if the single-stage process does not have a copper rich stage or a Ga gradient, which is likely since there was no change of the elemental fluxes during absorber layer growth and no Ga profile was measured. KF was added by post-deposition only. Current-voltage characteristics were measured and net doping concentrations were determined from capacitance-voltage measurements (CV). We see an improvement of the open-circuit voltage (Voc) with increasing KF amount, and a marginal increase of the fill factor. CV measurements showed increasing net acceptor concentration with increasing KF amount. Time resolved photoluminescence (PL) showed an increased decay time for KF treated cells and the PL peak shape changed. Without KF treatment the PL peak is symmetric, after KF treatment a further peak appears at higher energy in the PL spectrum. This higher energy peak increases in intensity with increasing KF concentration. The same effects were seen in a sample without Na, but here the Voc was limited due to large tailing. Hence both Na and K are required for good cell efficiencies.