Progress in Photovoltaics

While shingled cells have been around for a while, Tongwei’s adoption of the technology is notable as it is a manufacturer with considerable scale. If shingling can overcome some hurdles, it could prove a welcome solution as unshaded sites for PV become elusive in mature solar markets.

New research from UNSW in Australia outlines the need for solar cell and module makers to reduce or eliminate the use of silver in their products. Based on expected PV growth, in line with climate change commitments, solar manufacturers would require at least 85% of global silver reserves, according to the new study.

US scientists recently put different bifacial solar cells and modules through a series of tests at elevated temperature, humidity, voltage and mechanical stress levels. The tests revealed a range of light-induced and potential-induced degradation mechanisms that modules will likely suffer in the field.

A new study of the environmental impacts of renewable energy finds significant opportunities for solar to reduce its impacts in various categories, including human health, resource depletion, and environmental damage. The study notes in particular that more work is needed to establish a comprehensive reuse and recycling network for end-of-life PV products.

Scientists in the Netherlands have developed a model to forecast the energy yield of a PV system. It is able to take into account factors such as partial shading and multiple module orientations. Tested against a reference cell and pyranometer, the model showed less than 5% error, and the scientists claim their approach is up to three orders of magnitude faster than more common approaches using complex ray tracing.

US scientists have tested a range of modern cell designs under strong ultraviolet light and have found that many of them, including p-type PERC and n-type heterojunction cells, are more susceptible to degradation than older back surface field designs. They noted that the rear side of bifacial cells may be particularly vulnerable.

Perovskite-silicon tandem cells offer one of the surest pathways to much higher solar efficiencies, one that has moved close to commercialization in the past few years. Much of the work getting to this stage has naturally focused on developing a viable perovskite top cell. Optimizations to the silicon layer underneath, however, will also be important to the overall device function and efficiency. Scientists in Germany examined five different silicon cell concepts similar to those in mass production today, finding that with a few optimizations these could reach efficiencies up to 30.4%.

Scientists at Germany’s Fraunhofer Insititute for Solar Energy Systems (ISE) evaluated the performance of its newly introduced ‘Matrix’ approach to interconnecting shingled solar cells. The institute finds that, thanks to optimized current flows, energy yield of the Matrix approach could almost double that of standard shingled cell interconnection under random shading conditions.

Scientists in Germany applied vapor-based deposition techniques and laser scribed interconnection – both well established processes in existing thin-film solar manufacturing – to fabricate perovskite mini modules. The group achieved a maximum efficiency of 18% for a device measuring 4cm². Relying on these processes, they say, could simplify processing and reduce losses associated with scaling up to commercial-sized devices.

Scientists in Germany investigated various routes to optimizing cell design for perovskite-silicon tandem products. Beyond the perovskite layer itself, they note several other areas that should be optimized for tandem cells, taking silicon heterojunction processing as a starting point. The research identifies several routes to cut costs in cell production, including a significant reduction in indium consumption.