Ankit Singhania on PERC, TOPCon, and HJT in Solar Industry

There are two upcoming technologies in the module manufacturing industry named as TOPCon and HJT. Chinese module manufacturing giants have already adopted TOPCon and HJT and in India also we’re in the transition phase of adopting the same. Indian module manufacturers have already installed PERC in the past 2-3 years and will shift to TOPCon and HJT in the upcoming 2-3 years. We, at Navitas Solar, a leading module manufacturing company, have the installed capacity of 500 MW p.a. of PERC technology which will be upgraded to the TOPCon technology in the upcoming 2-3 years. In our recent expansion, we have launched new modules Bonito which are available in 9 & 10 Bus Bars in 144 & 156 cells with the capacity to generate 430 to 600 watts per panel.

Considering TOPCon technology, TOPCon(Tunnel Oxide Passivated Contact) solar cell is treated as the next-generation technology of PERC. TOPCON has an N-Type Silicon substrate and a thin tunneling oxide is applied, followed by a layer of highly doped with n or p poly silicon that contacts the metal at the ends. These tunneling oxide blocks one type of carrier and thus they are called passivating contacts. By changing the substrate material from P-Type silicon to N-Type silicon material the existing PERC line in the market can be upgraded to TOPCON structure by just adding the tunneling passivation layer.

Talking about HJT technology, Heterojunction technology (HJT) is a method for solar module manufacturing that is rising over the last 10 years. Nowadays, it is the most effective process for achieving the highest efficiency and power output. HJT technology is a combination of crystalline silicon and amorphous thin-film silicon. The top layer of amorphous silicon catches sunlight before it hits the crystalline layer, the middle layer turns out most of the sunlight into electricity and the last layer of crystalline silicon captures the remaining photons that surpass the first two layers. Three-layered technology allows more energy to be harvested resulting in achieving efficiencies of 25% or higher.

TOPCon cell can reach 28.7 % efficiency whereas HJT can reach 27.5% and PERC can reach 24.5% theoretically. From mass production efficiency, PERC has reached 23% while TOPCon and HJT have reached greater than 24%. There is still a long way to reach theoretically proven efficiency and there’re still many chances for improvements in the manufacturing line.

PERC is the most mature technology of the time, while TOPCon needs to add diffusion, etching, and deposition equipment to the PERC production line. Basically, in the PERC production line, TOPCon technology can be incorporated with some modifications. The cost of these modifications required in the PERC line for TOPCon technology is small. On the other hand, HJT solar cell process is the simplest but needs to completely replace the whole PERC manufacturing line in which more capital is required.

PERC Industrialization is the fastest and the cheapest while TOPCon solar cell has the highest compatibility, it can be upgraded from PERC/PERT technology followed by IBC. For HJT, a completely new line is required to install. Talking about cost perspective, the highest investment is required in installing the HJT line followed by TOPCon followed by the PERC line. In other words, TOPCon and PERC technology are highly compatible with additional equipment for deposition. Upgrading the PERC line with TOPCon will cost-effectively lengthen the equipment life cycle. Currently, the efficiency of mass production has improved significantly.

Discussing the number of processes, PERC has 8 processes while TOPCon has 10 processes whereas HJT only has 4 processes. The production cost of an HJT solar cell is Rs. 10.73/watt which is higher than the cost of PERC which is Rs. 8.34/watt. More domestic players are preferring HJT line equipment which leads to the continuous decline in the price of core equipment. Both old and new players are entering in HJT and so the expansion of HJT in the solar industry has been accelerated nowadays. There is a lot of space for efficiency improvement in HJT solar cells as well as a lot of room for equipment reduction cost also.

As soon as inventory opens up in the solar market, leading manufacturers will be benefitted from TOPCon upgradation. For the HJT line, a lot of effort is required to localize and make it mainstream technology. The cost of Manufacturing HJT cells is higher than PERC cells. In HJT, Double sided symmetrical structure increases the power generation rate. Also, low-temperature co-efficient (low heat loss), more stability, and low light attenuation are added advantages of HJT technology. The degradation rate is also lesser in HJT technology.

Some manufacturers across the solar industry have expansion plans to shift to N-type technology production lines. We foresee that in the next 3 years, the manufacturing capacity for TOPCon will increase by 20%.