Evert Eugène Bende

High Efficiency n-Type Metal-Wrap-Through Cells and Modules Using Industrial Processes

We report on our high efficiency n-type metal-wrap-through (MWT) cell and module technology. In this work, bifacial n-type MWT cells are produced by industrial processes in industrial full-scale and pilot-scale process equipment. N-type cells benefit from high recombination lifetime in the wafer and bifaciality. Also low-cost screen printed cells can yield over 20% efficiency. When combined with MWT technology, high-power back-contact modules result, which can employ very thin cells. We report a cell conversion efficiency of 20.5% (in-house measurement, certification pending), a significant gain compared to our earlier work. We will discuss performance of thin cells relative to thicker cells, comparing experimental results to modeling. Recently, two aspects of (mainly p-type) MWT technology have received increased attention: paste consumption and performance under reverse bias. We will discuss MWT paste consumption, showing how MWT technology, like multi-busbar technology, can support very low paste consumption. We also report on behavior of cells and modules under reverse bias. We also discuss the robustness of MWT technology to dissipation in hot spots under reverse bias. Finally, full-size modules have been made and cell-to-module ratios of the different I-V parameters were analysed. Modules from cells with average efficiency over 20% are pending. This work shows that low-cost n-type bifacial cells are suitable for industrial high efficiency back-contact technology.

Tessera: Scalable, shade robust module

This paper describes the development and output measurements on a new shade robust module, named the Tessera module. This module uses a novel electrical configuration, comprised of shade independent blocks protected by in-laminate diodes, with a mixture of series and parallel connections. By using ECNs existing back contact technology [1], no significant additional manufacturing costs occur. The design, method and manufacturing technology will be explained. The module leads to an increased annual output in case of shading and an increase in system safety due to lower heat dissipation: of 40°C instead of 130°C compared to standard diodes, and reduced failure of components. Annual yield has been calculated showing significant gains.

Tessera: Maximizing PV Yield Performance with Size Flexibility for BIPV

Application of PV in the built environment, both as BAPV and BIPV, requires improved aesthetics, decreased operating temperatures of the modules and diodes, improved output under partial shading and reduced production costs while allowing the size and shape of the PV elements to be more flexible. ECN presents TESSERA: a novel PV module lay-out which allows linear shade performance, while at the same time allowing size and manufacturing flexibility which also leads to improved aesthetics as entire roof and façade areas can be utilized. Temperature measurements on module diodes shows the diodes in these PV modules only reach a temperature of 40uf0b0C compared to 140uf0b0C for conventional ones. Mechanical load tests to rails glued to the rear of the PV modules shows the interconnections are stable, allowing vertical, frameless installation. Hence, these TESSERA elements allow broader application of PV in the built environment.

23% Efficiency metal wrap through silicon heterojunction solar cells

MWT-SHJ cells and modules combine the positive benefits of both underlying technologies: namely high Voc, higher Jsc and higher FF. Especially the FF is maintained before and after encapsulation thanks to the rear interconnection which strongly reduces cell to module FF losses. We obtained two record efficiencies for these devices with two different front metallizations: 22.6% using low temperature Ag paste and 23.1% using copper plating. Voc values above 730 mV have been achieved also in the new 6×6 vias metallization, demonstrating that the architecture maintains the exceptional passivation typical of heterojunction devices. The MWT cell and module structure offers even greater advantages on heterojunction solar cells: i) front side Ag consumption reduction up to a factor two; ii) concurrent low temperature cell interconnection and encapsulation. Our record MWT-SHJ solar cells and modules are manufactured using industrially proven tools and 6 inch commercial n-type Cz Si wafers. The metallization choice gives ample room to manufacturers for optimization based on internal cost structure, material costs and business strategy. MWT-SHJ behavior at reverse bias voltage and low illumination intensity is comparable to conventional HJ devices.

Metal wrap-through cell and module design optimization

Back-contact modules made using a conductive back-sheet foil have a number of advantages over conventional H-pattern modules including a higher power output, compatibility with very thin cells and efficient and high yield manufacturing. In this paper, we present the results of efficiency and material optimization for cost reduction when using metal-wrap-through (MWT) cells. This includes the use of an aluminum conductive back-sheet, a thinner encapsulant for reduced conductive adhesive consumption and an increased number of vias in the cell. Experimental and modelling results show that the cell and module performance can be improved at a reduced module costs (4% lower than current cost) whilst retaining reliability.

An alternative corrosion resistance test method for solar cells and interconnection materials limiting the number of long-lasting and expensive damp-heat climate chamber tests

Damp-heat testing of PV modules is a time-consuming process, taking months. We present an alternative test method: electrochemical noise (EcN) measurements. Data acquisition times vary between minutes for direct exposure to several tens of hours for encapsulated samples. EcN measurements are presented for several solar cell concepts and different environments. We have found that the degradation in damp-heat testing is proportional to the electrochemical noise signal. In conclusion, the electrochemical noise measurements are a fast, versatile tool to test the corrosion resistance of solar cells, which can be tested for different environments including encapsulation.