According to the International Technology Roadmap for Photovoltaics, passivated emitter and rear solar cells dominate the market in 2021 of up to 80% and are forecast to remain state of the art at least for the next 5 years. Within the production process of solar cells, it is typical to have cells with lower efficiency grades due to variations in manufacturing processes or material defects. Reprocessing such solar cells could save cost due to increased production yield and simultaneously reduced cost for recycling of unusable/unsellable low‐efficiency cells. Herein, the impact of the laser‐enhanced contact optimization (LECO) process on the power output and reliability of solar modules using commercial off‐spec cells of different manufacturers is analyzed. LECO is a downstream process for optimizing metal−semiconductor contacts on finished solar cells. The treatment leads to a significant economic gain due to enhanced cell efficiency (Wp ↑, therefore manufacturing cost per Wp ↓) even of already good solar cells. Herein, the first evaluation of the impact of the LECO process on the cell output power on an industrial scale (>1000 cells) and on module reliability is presented. The results for common short‐term effects like light‐induced degradation and light‐ and elevated temperature‐induced degradation are within expected limits and the durability against, for example, potential‐induced degradation is not changed due to the LECO process. The results further show that cell sorting is crucial for a reliable module and to avoid outliers in terms of unexpected degradation and recovery phenomena of individual cells.

Within this contribution several 3D finite- element- models have been created in order to simulate processing of solar cells (lamination, soldering) as well as mechanical bending. The stress state for each load case was analysed with respect to magnitude and direction of principal stresses. For the process steps there are different mechanisms that induce stresses in the silicon. For soldering the mismatch in CTE is dominant. For lamination, bending around the ribbon is the dominant mechanism, which is due to the contraction of the encapsulant. Furthermore, it was found that cooling during lamination applies the highest loads into a solar cell. Mechanical bending was simulated and investigated experimentally by 4-point-bending with different load ramps. Due to strain-rate dependent properties of the encapsulant EVA there is a minor in fluence on the load deflection behaviour but a large influence on the reliability of a solar cell. By means of a parameter study the influ ence of the cell distance on mechanical reliability was investigates. It was shown that a small cell distance (here < 3mm) increases the probability of failure of the solar cell significantly

No abstract

No abstract