The new era of silicon and perovskite photovoltaics
When working with solar technology every performance increase of the cells is fundamental. But equally important is to be able to bring that improvement also at the module level, passing from laboratory to industrial dimensions. A lesson well learned from the British company Oxford PV and the German institute Fraunhofer ISE, developers of full-format tandem photovoltaic modules with unique efficiency.
The panels use cells produced by Oxford PV itself. These units are made by depositing a thin perovskite film on a conventional silicon solar cell. The devices, in M6 format, can convert 28.6% of solar energy into electricity, a value that in May last year earned the company a world record. Today the company has launched a first line of tandem cells in Brendenburg for partner panel manufacturers. But the ambition of Oxford PV points high and today amazes with the tandem solar module in silicon-perovskite, glass-glass and industrial format, the most efficient in the world. The scientists of the Fraunhofer ISE realized it using their production laboratory Module – TEC, a unique infrastructure for the manufacture and testing of solar panels.
Are Tandem photovoltaic modules, ready for the market?
The operation required special attention from scientists. Perovskites are compounds highly sensitive to environmental factors, which could be damaged by conventional manufacturing techniques. That’s why the team has developed low-temperature processes to connect and encapsulate solar cells. These approaches are suitable for large-scale industrial production, explains Dr Achim Kraft of the Fraunhofer ISE, and are easily applied to commercial systems. “The necessary adaptations can be easily implemented even in today’s photovoltaic production lines“.
At this point, the Institute’s CalLab PV Modules calibration laboratory used a new multispectral solar simulator to determine panel efficiency. Key step. To provide accurate and reproducible information on the power of the new tandem photovoltaic modules both the perovskite layer and the silicon one must be illuminated by different LED light sources to reproduce natural light in the most faithful way possible.
Under these conditions, the researchers calculated conversion efficiency using an area of 1.68 square meters. The result? Perovskite/Yes can convert 25% of the light into electricity, showing a peak power of 421 watts. And that’s just the beginning. Silicon/perovskite double junction solar cells have a theoretical maximum efficiency of more than 43% – 13 percentage points more than pure crystalline silicon solar cells – and any progress towards this target could increase module yield. The next step? Fraunhofer ISE and Oxford PV are now working towards the certification of the record-breaking module and intensive testing on long-term stability is already underway.