A new report, drawn up by 41 experts from around the world, provides the state of the art on a series of photovoltaic technologies, highlighting key applications and pathways towards marketing
Photovoltaics: where does innovation go?
From new materials to innovative concepts. From projects to improve light management and strategies to overcome current limits of efficiency. From the most promising applications to unresolved problems. The “Status report on emerging photovoltaics“, drawn up by a group of 41 international experts, offers an interesting overview of emerging photovoltaic technologies. The document has been published in recent days in the Journal of Photonics for Energy and through vertical sections launches a look at the state of the sector, discussing the challenges still open and the tools to address them.
An overview designed to be “a useful resource for people inside and outside the industry”. “The various contributions – explains JPE’s chief editor, Sean Shaheen, professor at the University of Colorado Boulder and co-author of the report – demonstrate the remarkable range of emerging photovoltaic technologies as well as developments in their applications. They also describe some of the challenges for widespread implementation”.
The main emerging photovoltaic technologies?
But what are the emerging photovoltaic technologies analyzed? In the field of silicon, the semiconductor number one for solar, it ranges from double-sided photovoltaic to black silicon or nanostructured. While for the first one, there is a solid future, also because it is supported by the main cell architectures (PERC/PERL/PERT/Topcon), for the second the industrial feasibility seems much more complex. And it would need a more in-depth analysis of cost and life cycle.
On innovations in the field of thin film photovoltaics, the authors report the foundations and limits of efficiency of two series of materials: the CIGS and CdTe (the most widespread thin film technology). In the first case, it happens that the technology has suffered a lot from the gap between the efficiency of the cells and that of the modules and as it is possible to eliminate such gap “using absorbers with wider band gaps, designing new ways to assemble cells into modules and developing more transparent conductive contacts”. In the second case, CdTe modules can already compete with silicon modules in some markets, with lower energy depreciation times and lower environmental impact. But experts point out that a further increase in efficiency would cut costs.
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Organic photovoltaics, however, still brings with it many challenges to solve. The authors highlight how in the case of semitransparent organic solar cells it is necessary to improve both performance and average visible transmittance by incorporating materials that absorb the near infrared in the active layer. Also addressing the issue of stability, is necessary to achieve commercial feasibility in large-area applications.
Dye-sensitized solar cells (DSSC) or Graetzel cells have come a long way, but commercial scalability is hampered by charge recombination, the main cause of efficiency loss in this technology.
There is a large chapter on perovskites whose contribution to emerging photovoltaic technologies comes mainly from tandem or multi-junction architectures. The stacking of a subcell in perovskite on a crystalline silicon today promises to increase the conversion efficiency by over 30% and to reduce the leveled costs of electricity. One of the main challenges in this case is to be able to scale laboratory products. The perovskite silicon tandem photovoltaic breaks a new record.
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Photovoltaic applications of tomorrow
“One of the emerging and most flourishing areas of photovoltaics is the collection of internal light“, writes the authors of the report. “The progress of indoor photovoltaics is stimulated by the rapid development of the Internet of Things (IoT) and the urgency of making this technology more sustainable and durable”. The most promising materials for this purpose so far are amorphous silicon, DSSC, organic photovoltaic and perovskites halide.
But among the most promising short-term applications of emerging photovoltaic technology, it is agriculture to dominates the sector. For the experts, the agrivoltaic is conquering the market, followed by the integrated systems in the car parks, from those destined for the Space, to the IoT, to the automotive. At the same time, a sort of trend for “geographically tailor-made” photovoltaics is strengthening, aimed at designing spectral and temperature responses, stability characteristics and test protocols for more Nordic conditions.
