Promising Solar Cell Manufacturing Technology – An Investor’s Dilemma
Since solar cell manufacturing is a capital-intensive industry, any investment to meet price targets has to be volume- and quality (efficiency)- driven to sustain in the market. As a result, several million-dollar investments are made with the support of trained professionals in that technology.
May 13, 2025. By News Bureau
With the growing population and pollution across the globe, the search for viable technology for solar cell manufacturing (working as a green energy resource) has been ongoing for five decades or more. Every time, something new and better supports the green cause through solar cell manufacturing technology.
It is always an uphill task for an unsuspecting and naïve investor to choose the most appropriate and viable technology, which not only gives handsome returns on investment but also supports the ultimate cause of the green revolution.
Most of the time, such investments face rough weather despite having a well-trained and experienced set of technical prodigies. This is because the pace at which technology is advancing and changing outpaces the imaginations and projections.
Technology Obsolescence
A prime example has been the sudden shift from multi-crystalline technology to mono-crystalline technology based on PERC cells. Multi-crystalline technology was at the helm of affairs and was a surefire success for an investor for more than three decades.
Since solar cell manufacturing is a capital-intensive industry, any investment to meet price targets has to be volume- and quality (efficiency)-driven to sustain in the market. As a result, several million-dollar investments are made with the support of trained professionals in that technology. The entire ecosystem, including raw materials (expensive ones), is also developed along with it.
The market shift from multi - BSF cells to PERC cells led to several important changes. Equipment became redundant, only worth their salvage value. This happened not only for solar cell manufacturing but also necessitated modifications in the wafer industry and others.
However, the distinct efficiency advantage ruled in favour of PERC, and overnight, solar cell manufacturers and wafer manufacturers decided to bring in new equipment for PERC cells and P-type mono wafers. This left many manufacturing lines redundant in both the wafer and solar cell industries.
This led to multi-wafer becoming expensive, and cell manufacturers who could not afford new equipment for PERC had to shut down their operations, causing investment losses.
Only two or three years after PERC technology adoption, there was again a shift in wafer types from P-type to N-type, and new N-type based technologies such as TOPCon and HJT emerged to challenge PERC.
TOPCon technology has already become the choice of investors, and in China alone, more than 700 GW of TOPCon technology is on the floor, enough to wipe out PERC's dominance.
This article attempts to analyse the entire technology spectrum of various promising technologies for solar cell manufacturing and examines the suitability of one over the other, looking for stability for at least a five-year horizon. This can definitely help investors or decision-makers make informed choices.
PERC, HJT, TOPCon, and Beyond
This article will reference past data in general and will try to speak more in a generic manner to express the views. A comparison of PERC, HJT, and TOPCon is provided in detail, with a conclusion drawn at the end. These technologies are currently making headlines.
PERC Cell
PERC or Passivated Emitter Rear Cells is a technology that takes advantage of surface passivation on the rear side of silicon using a silicon nitride layer and also emitter passivation. The use of mono material over multi-crystalline gives the additional advantage of a higher minority carrier lifetime. As a result, it is possible to achieve up to 24.2 percent efficient solar cells, while in volume production, 23 percent PERC cells are regularly produced at the gigawatt level. The development of PERC cells from 19 percent to 21-23 percent gave enough margin to switch from multi to mono PERC. The industry comfortably mass-produced 23.0 percent cells, with some reaching up to 24 percent. However, there were two issues with this technology that led to the industry quickly shifting to other technologies:
It is always an uphill task for an unsuspecting and naïve investor to choose the most appropriate and viable technology, which not only gives handsome returns on investment but also supports the ultimate cause of the green revolution.
Most of the time, such investments face rough weather despite having a well-trained and experienced set of technical prodigies. This is because the pace at which technology is advancing and changing outpaces the imaginations and projections.
Technology Obsolescence
A prime example has been the sudden shift from multi-crystalline technology to mono-crystalline technology based on PERC cells. Multi-crystalline technology was at the helm of affairs and was a surefire success for an investor for more than three decades.
Since solar cell manufacturing is a capital-intensive industry, any investment to meet price targets has to be volume- and quality (efficiency)-driven to sustain in the market. As a result, several million-dollar investments are made with the support of trained professionals in that technology. The entire ecosystem, including raw materials (expensive ones), is also developed along with it.
The market shift from multi - BSF cells to PERC cells led to several important changes. Equipment became redundant, only worth their salvage value. This happened not only for solar cell manufacturing but also necessitated modifications in the wafer industry and others.
However, the distinct efficiency advantage ruled in favour of PERC, and overnight, solar cell manufacturers and wafer manufacturers decided to bring in new equipment for PERC cells and P-type mono wafers. This left many manufacturing lines redundant in both the wafer and solar cell industries.
This led to multi-wafer becoming expensive, and cell manufacturers who could not afford new equipment for PERC had to shut down their operations, causing investment losses.
Only two or three years after PERC technology adoption, there was again a shift in wafer types from P-type to N-type, and new N-type based technologies such as TOPCon and HJT emerged to challenge PERC.
TOPCon technology has already become the choice of investors, and in China alone, more than 700 GW of TOPCon technology is on the floor, enough to wipe out PERC's dominance.
This article attempts to analyse the entire technology spectrum of various promising technologies for solar cell manufacturing and examines the suitability of one over the other, looking for stability for at least a five-year horizon. This can definitely help investors or decision-makers make informed choices.
PERC, HJT, TOPCon, and Beyond
This article will reference past data in general and will try to speak more in a generic manner to express the views. A comparison of PERC, HJT, and TOPCon is provided in detail, with a conclusion drawn at the end. These technologies are currently making headlines.
PERC Cell
PERC or Passivated Emitter Rear Cells is a technology that takes advantage of surface passivation on the rear side of silicon using a silicon nitride layer and also emitter passivation. The use of mono material over multi-crystalline gives the additional advantage of a higher minority carrier lifetime. As a result, it is possible to achieve up to 24.2 percent efficient solar cells, while in volume production, 23 percent PERC cells are regularly produced at the gigawatt level. The development of PERC cells from 19 percent to 21-23 percent gave enough margin to switch from multi to mono PERC. The industry comfortably mass-produced 23.0 percent cells, with some reaching up to 24 percent. However, there were two issues with this technology that led to the industry quickly shifting to other technologies:
- Due to the presence of boron atoms in P-type material, there was initial degradation of more than 2-3 percent. This was due to the use of P-type mono material. Additionally, the temperature coefficient was (- 0.4%) or worse, leading to poor power generation in the field, particularly in high-temperature areas.
- There was an upper theoretical limit of 24.2 percent in PERC technology, and almost saturation in efficiency was realised by many producers.
Both deficiencies were practically absent in the two new upcoming manufacturing technologies, namely HJT and TOPCon. As a result, the industry quickly started looking for alternatives to PERC, and rightly so.
Given the current context, it is not recommended to invest in PERC for the following disadvantages:
Given the current context, it is not recommended to invest in PERC for the following disadvantages:
- There is an upper theoretical limit of efficiency, which is below the starting efficiency levels of HJT or TOPCon.
- Since the wafer industry is shifting to N-type silicon material, the availability of P-type mono is becoming difficult, and if available, prices are likely to be very high.
- LID losses and power loss due to high temperature coefficients make LCOE (Levelised Cost of Energy) high and undesirable.
HJT Technology
HJT technology has been an interesting technology developed initially by Sanyo, Japan, in the late 1980s. It was named HIT (Hetero Junction with Intrinsic Thin Layer), a technology developed to utilise the potential of thin-film technologies (amorphous materials in thin layers). These thin layers, both doped and undoped, offer high absorption of the solar spectrum, leading to higher efficiencies. Sanyo achieved 21 percent efficient cells when multi-crystalline technology was struggling at around 14 percent. This technology used N-type silicon with thin amorphous silicon layers on either side to make PIN junctions.
Technologically speaking, it was a brilliant effort to enhance solar device performance significantly. However, for nearly two decades or more, this technology did not see mass-scale adoption. Possible reasons include:
HJT technology has been an interesting technology developed initially by Sanyo, Japan, in the late 1980s. It was named HIT (Hetero Junction with Intrinsic Thin Layer), a technology developed to utilise the potential of thin-film technologies (amorphous materials in thin layers). These thin layers, both doped and undoped, offer high absorption of the solar spectrum, leading to higher efficiencies. Sanyo achieved 21 percent efficient cells when multi-crystalline technology was struggling at around 14 percent. This technology used N-type silicon with thin amorphous silicon layers on either side to make PIN junctions.
Technologically speaking, it was a brilliant effort to enhance solar device performance significantly. However, for nearly two decades or more, this technology did not see mass-scale adoption. Possible reasons include:
- High capex due to complex processing capabilities involving thin-film depositions (e.g., PECVD, PVD) that use several types of hazardous gases, leading to higher equipment costs.
- Opex was also very high (almost three times that of multi-crystalline technology) due to the use of silver conducting pastes suitable for low temperatures, with the quantity almost double compared to crystalline technologies.
- Issues related to thin-film technologies, particularly field-related degradation.
Therefore, after 2010, following the expiration of basic patents from Sanyo, the world started developing this technology, naming it HJT (Hetero Junction Technology) or SHJ (Silicon Hetero Junction). It was not limited to Chinese players in PV but also involved Europeans who began making equipment for HJT. Meyer & Berger offered very promising tools to reach 24-25 percent efficiency. In fact, Sanyo also sold this technology to Panasonic, which set up a 160 MW annual capacity plant in Malaysia with a promise to expand further.
However, over time, none of these companies scaled up in HJT technology. In fact, Meyer & Berger decided to close this activity after setting up one or two non-functional or semi-functional plants in Europe.
In the initial years of HJT growth, a few companies like SC and Maxwell started making manufacturing tools for GW-scale HJT plants. Yet, the overall capacity for HJT has not even crossed 100 GW, possibly due to the reasons mentioned above (high capex, high opex, and long-term stability issues in the field).
Potential Advantages of HJT Technology:
While HJT technology is not without merit, there are definitely potential benefits:
However, over time, none of these companies scaled up in HJT technology. In fact, Meyer & Berger decided to close this activity after setting up one or two non-functional or semi-functional plants in Europe.
In the initial years of HJT growth, a few companies like SC and Maxwell started making manufacturing tools for GW-scale HJT plants. Yet, the overall capacity for HJT has not even crossed 100 GW, possibly due to the reasons mentioned above (high capex, high opex, and long-term stability issues in the field).
Potential Advantages of HJT Technology:
While HJT technology is not without merit, there are definitely potential benefits:
- Low temperature coefficient, leading to better LCOE.
- Use of less silicon (up to 100 micron thick silicon wafers).
- Fewer process steps, leading to better manufacturability.
- A higher and adaptable roadmap — this technology has the potential to reach up to 27 percent in mass production (presently it is at 24-24.5 percent) and can also be integrated with perovskite cells to make tandem cells exceeding 30 percent. However, this target is more than five years away due to stability issues of the perovskite material itself.
That said, HJT technology today can be considered better than PERC, but it is still not production-worthy due to high capex and high opex costs. Also, several local requirements could add costs due to the handling of very toxic gases.
Thus, this cannot be an option for investors seeking good and viable returns in the present context.
TOPCon Cells
TOPCon cells, short for ‘Tunnel Oxide Passivated Contact’ cells, have a thin layer of silicon oxide and a thin layer of doped silicon on an N-type silicon substrate. These two layers form a passivating contact that reduces charge carrier recombination, improving cell efficiency.TOPCon cells are known for their low temperature coefficients and spectral response, making them ideal for use in tropical, humid, and hot climates.
TOPCon cells began with 24.5 percent efficiency, which outnumbered PERC cells' efficiency at that time. It grew very fast, and in China, several companies started making TOPCon cells for mass production at high volumes. As a result, an ecosystem from wafer manufacturing to equipment and facilities developed around TOPCon technology in China, while Europe and other countries limited development to lab-level research. China made a quantum leap and demonstrated to the world that TOPCon technology is the future.
There is no doubt that, due to the following factors, TOPCon is going to lead for at least a decade with inbuilt improvement potential:
Thus, this cannot be an option for investors seeking good and viable returns in the present context.
TOPCon Cells
TOPCon cells, short for ‘Tunnel Oxide Passivated Contact’ cells, have a thin layer of silicon oxide and a thin layer of doped silicon on an N-type silicon substrate. These two layers form a passivating contact that reduces charge carrier recombination, improving cell efficiency.TOPCon cells are known for their low temperature coefficients and spectral response, making them ideal for use in tropical, humid, and hot climates.
TOPCon cells began with 24.5 percent efficiency, which outnumbered PERC cells' efficiency at that time. It grew very fast, and in China, several companies started making TOPCon cells for mass production at high volumes. As a result, an ecosystem from wafer manufacturing to equipment and facilities developed around TOPCon technology in China, while Europe and other countries limited development to lab-level research. China made a quantum leap and demonstrated to the world that TOPCon technology is the future.
There is no doubt that, due to the following factors, TOPCon is going to lead for at least a decade with inbuilt improvement potential:
- TOPCon technology has an ultimate potential of 27.5 percent cell efficiency.
- Its low temperature coefficient, low LID, and LETID make it comparable to HJT in LCOE performance and much superior to PERC.
- Due to competitive capex and opex, along with technological simplicity compared to HJT, it is better suited.
- There is no abnormal degradation, making it a superior technology.
- It has a defined roadmap. This technology is also adaptable to back-contact and tandem technologies using perovskite cells, thus realising 27.5 percent plus efficiency in two years, and beyond 30 percent using perovskite cells within five to ten years.
- Interestingly, all these technologies can be serially added to TOPCon productions without major overhauling of existing lines.
This leads to long-term stability and the longevity of capex investments – beyond 5-10 years.
Further, if we look at the basic process of TOPCon, it involves the deposition of an oxide and N-layer.
PECVD and LPCVD Technology
For oxide and N-layer deposition, either PECVD or LPCVD technology can be used. If we look at LPCVD technology, it was initially used in the semiconductor industry, where per-day wafer processing was less, making quartz tube replacement or breakage infrequent.
However, in the solar industry, wafer processing runs into several lakhs per day for a GW facility, leading to contamination and quartz tube breakage, which causes frequent stoppages. This affects functional parameters such as efficiency.
Additionally, the process steps for oxide deposition and N-type deposition cannot be done in situ, requiring wafer handling and reducing throughput.
TOPCon process with PECVD, on the other hand, has no major contamination of quartz tubes, and no significant wrap-around deposition, and both processes can be done in the same tube, reducing wafer handling.
Therefore, with PECVD, TOPCon offers significant intermediate gains, such as poly finger and bi-poly depositions, improving efficiency from 26.5 percent to 27.5 percent even without a back-contact design.
TOPCon, with PECVD, thus has a roadmap to reach 30 percent and beyond on its normal growth path.
Therefore, out of the current technology spectrum, TOPCon solar cell manufacturing using PECVD technology is a risk-free investment decision. Additionally, the entire ecosystem around this technology supports it in providing solutions for the green revolution at increasingly affordable costs.
Other Technologies
Some other technologies being tried for decades are either not the best option or should not be considered at all. At best, they can be useful for a small niche market. These technologies include solar concentrator technology, thin-film technology (based on amorphous silicon, CdTe, CIS, CIGS), GaAs, GaAlAs, and organic compound semiconductor-based technology.
Though these technologies have excellent technical promise and are creditworthy, they do not provide solutions to the multi-GW industry at economically viable options. Hence, they will continue for research and development work and are not likely to give a cost-effective and better-than-TOPCon technology solution to the industry in at least the next ten years.
Further, if we look at the basic process of TOPCon, it involves the deposition of an oxide and N-layer.
PECVD and LPCVD Technology
For oxide and N-layer deposition, either PECVD or LPCVD technology can be used. If we look at LPCVD technology, it was initially used in the semiconductor industry, where per-day wafer processing was less, making quartz tube replacement or breakage infrequent.
However, in the solar industry, wafer processing runs into several lakhs per day for a GW facility, leading to contamination and quartz tube breakage, which causes frequent stoppages. This affects functional parameters such as efficiency.
Additionally, the process steps for oxide deposition and N-type deposition cannot be done in situ, requiring wafer handling and reducing throughput.
TOPCon process with PECVD, on the other hand, has no major contamination of quartz tubes, and no significant wrap-around deposition, and both processes can be done in the same tube, reducing wafer handling.
Therefore, with PECVD, TOPCon offers significant intermediate gains, such as poly finger and bi-poly depositions, improving efficiency from 26.5 percent to 27.5 percent even without a back-contact design.
TOPCon, with PECVD, thus has a roadmap to reach 30 percent and beyond on its normal growth path.
Therefore, out of the current technology spectrum, TOPCon solar cell manufacturing using PECVD technology is a risk-free investment decision. Additionally, the entire ecosystem around this technology supports it in providing solutions for the green revolution at increasingly affordable costs.
Other Technologies
Some other technologies being tried for decades are either not the best option or should not be considered at all. At best, they can be useful for a small niche market. These technologies include solar concentrator technology, thin-film technology (based on amorphous silicon, CdTe, CIS, CIGS), GaAs, GaAlAs, and organic compound semiconductor-based technology.
Though these technologies have excellent technical promise and are creditworthy, they do not provide solutions to the multi-GW industry at economically viable options. Hence, they will continue for research and development work and are not likely to give a cost-effective and better-than-TOPCon technology solution to the industry in at least the next ten years.
- Vijay Kumar, Chief Operating Officer, Zuvay Technologies Pvt. Ltd.
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