2021 was an interesting year for solar energy as it was a comeback year after a full 2020 COVID-19 lockdowns. The trending technologies in the field of solar energy in 2021 can be categorized into three main categories:
- New Technologies in the Solar Cell architecture
- New streams in photovoltaic panels production, Big Wafer Size
- Emerging innovative Solar Installations
In the new solar cell architecture category, TOPCon and HJT Have attracted more interest in the solar energy sector. The main driver of this shift in this segment is that PERC technology as another and prevalent technology has reached its threshold / limits around 24 to 25% efficiency. As a matter of fact, eight out of the top 10 solar panels in the Solar Edition’s December best Solar panels list were based on PERC technology, and only one released based on these two high-efficiency solar cells designs. However, this does not mean these technologies are not accepted among PV module manufacturers. Contrarily, it is a niche market that some giant PV module producers have invested massively in, and it is expected to be among areas that we hear a lot about in the coming years.
Another popular segment with PV module manufacturers in 2021 in order to achieve high power output is big wafer size. In late 2019, together with utilizing PERC technology to reach high efficiency and power output, the big wafer format also gained popularity among them. This also led to the formation of a bipolar in the market to specify which big wafer formats actually reduces bill of material (BoM), levelized cost of electricity (LCOE), as well as increasing power density.
As the last hot topic in 2021, the industry has faced new entries which date backs to several years ago. This category accounts for agrivoltaics (agriculture+photovoltaic), building integrated photovoltaic or BIPV (building+photovoltaic), and floating photovoltaic (FPV).
In the following paragraphs, we will go through the details of each category.
New Solar Cell Architectures: TOPCon & HJT Technologies
TOPCon or tunnel oxide passivated contacts is basically considered as the forthcoming and alternative technology to the current state-of-the-art passivated emitter and rear cell (PERC) solar cell design. The cell architecture is based on the concept of ‘passivating and carrier selective contacts’, where the recombination of minority charge carriers is suppressed by a stack of thin tunnel oxide and heavily-doped polysilicon (poly-Si) layers . The common industrial practice is to apply this structure on the rear side of the n-type solar cell. The TOPCon process involves some additional steps over the PERC production process. One such process is emitter formation via boron diffusion. Annealing might be another additional step, depending on the polysilicon doping mechanism . TOPCon has the highest theoretical efficiency potential at 28.7, while the highest lab efficiency of 26.1% has been reached by Institute for Solar Energy Research Hamelin (ISFH) . Several giant PV module manufacturers including Jolywood, LONGi Solar, and Jinko Solar have released products with this technology in 2021.
For example, Jinko Solar recently launched its well-known Tiger series with a New Variant, that is Tiger Neo. Tiger Neo 78HL 4 model with 22% efficiency and 615 W in its power output has utilized TOPCon technology in their solar cells . This PV module ranked second in SolarEdition’s December’s Top 10 Solar panels list . Jolywood also released its Niwa Max model with 22.53% efficiency and 700 W power output thanks to using TOPcon technology and one of trending big wafer formats, G12. This PV module with an unconventional cell number, 66 cells, entered neither 60 cells nor 72 cells SolarEdition’s Top 10 Solar panels. But it is suggested by the company for utility-scale PV projects. It is worth mentioning that the CapEx cost (capital expenditure) of TOPCon technology is roughly 20% higher than PERC .
Heterojunction technology (HJT) has a completely different flow in solar panel manufacturing. HJT achieves higher efficiency compared to PERC solar cell design due to being able to absorb a wide spectrum of sunlight. The HJT solar cell consists of three layers. It has gathered two different generations of solar cell manufacturing into one single cell. A solar cell based on HJT is made when a crystalline silicon solar cell is sandwiched between two layers of “amorphous silicon (a-Si)” solar cells. Therefore, amorphous layers absorb the extra photons that could not be captured by the middle crystalline silicon layer.
PV modules which are produced based on HJT technology have higher prices and production costs compared to PV modules with TOPCon solar cells. Moreover, Both of these trends have higher prices in comparison with PERC cells.
New streams in photovoltaic panels production, Big Wafer Format M10 & G12
As we mentioned earlier, the date of using big wafer format in PV module production dates back to 2019. This has led to an intense competition between two groups of PV module producers to introduce and specify the industry-standard wafer size for the solar PV sector . These two groups are called the “500+ PV module producer” club and Photovoltaic Open Innovation Ecological Alliance. The former has chosen an M10 wafer size as the mainstream for PV module production and aimed at reaching PV modules with power more than 500 W while the latter has selected M12/G12 wafer size to achieve products with more than 600 W in their power output . It is important to note that M10 and G12 have 182 mm and 210 mm side lengths respectively.
According to the 12th version of International Technology Roadmap for Photovoltaic (ITRPV) report, three newly wafer formats including M6, M10, and M12 will become the mainstreams of the PV module production by 2030 .
Emerging innovative Solar Installations, Agrivoltaics, BIPV & FPV
Installations of ground and rooftop-mounted PV modules will still be the norm in the solar industry. But some newly emerging and niche markets have become popular in 2021. There are agrivoltaics, BIPV, and FPV. These promising options aim at addressing reducing CO2 emissions as well as integrating solar into our existing environments .
These hot topics could possibly play an important role in the future directions in the solar energy sector to reach a carbon-neutral future.
 Kafle, B., Goraya, B. S., Mack, S., Feldmann, F., Nold, S., & Rentsch, J. (2021). TOPCon–Technology options for cost efficient industrial manufacturing. Solar Energy Materials and Solar Cells, 227, 111100.
 TaiyangNews, TOPCon Solar Technology 2021 report, 7th of December, Written by Shravan K. Chunduri & Michael Schmela.
 SolarEdition, “Top 10 Solar panels for December of 2021”.
 SolarEdition, “Two Wafer Sizes Will Disappear and Three ones Will Become Mainstreams by 2030”.
 ITRPV 2021, the 12th version of International Technology Roadmap for Photovoltaic, 2020 result.
 PV-Magazine, “A year in PV: Technology trends in 2021”, Written by Mark Huchins