Globally, solar PV installations today use Passivated Emitter and Rear Cell (PERC) technology which was introduced in the 1980s for bringing more power conversion efficiency to the modules. However, PERC is now reaching its practical efficiency limits, which opens the window for higher-efficiency cell technologies to be explored by PV module makers.

Over the years, Tunnel Oxide Passivated Contact or TOPCon solar cell technology has presented itself as a viable contender to be taking over from PERC for bringing in higher efficiency and lower degradation, among other benefits. The fact that it can be easily adapted to the current crop of PV production equipment that already produces PERC cells brings down the financial costs, which just adds to its attractiveness.

TaiyangNews discussed these aspects and more in our exclusive report on TOPCon solar technology launched in December 2021 during the CSPV conference in China. It can be downloaded for free by logging into your account on our website (see TaiyangNews TOPCon Solar Technology).

To take the discussion further, TaiyangNews brought together leading TOPCon solar technology manufacturer Jinko Solar along with German research institute ISFH and testing & certification firm TÜV Nord in a Special Focus Webinar on January 25, 2022, to discuss the many advantages of these modules and why TOPCon is considered the natural successor to incumbent PERC.

In his opening presentation, Prof. Dr. Robby Peibst, Head of Emerging Solar Cell Technologies at the Institute for Solar Energy Research Hamelin (ISFH)  shared the success story of poly-Si on oxide-based passivating contacts and said the efficiency potential of poly-Si on oxide junctions is on par with that of a-Si:H/c-Si heterojunction. Unlike most companies working on n-type TOPCon, ISFH has chosen to focus on the p-type version, as this is closer today’s commercial PERC solar cells. While the roadmap and efficiencies he showed were impressive – 26.1% for its POLO IBC cells, he did add that research institutes can hardly keep up with efficiency levels and development speed of industrial pilot lines hence the focus is on demonstration of principle feasibility.

The commercial manufacturer holding the current world record is JinkoSolar (see JinkoSolar: ‘Record’ 25.25% Efficiency For TOPCon Cell). In fact, among tier I solar PV manufacturers,  JinkoSolar is betting biggest on TOPCon technology as it aims to start mass production of its Tiger Neo modules in Q1/2022 and achieve 10 GW annual production capacity already by the end of 2022. While sharing a brief introduction of the Tiger Neo N-type TOPCon module, the company’s Global Product Manager Leo Cong said the manufacturer will go for a 620W TOPCon product in 2022 using 182mm wafer sized solar cell.

Cong underline that advanced N-type HOT 2.0 technology brings better temperature coefficients with higher bifacial factor and lower LID/LETID, and shared data from an outdoor project in China to claim that P-type bifacial module power gain for the installation was determined as 9.7%, while the TOPCon N-type bifacial module power gain was 12.7%.

To give an overview on TOPCon module performance around the world, JinkoSolar’s regional heads of technical services took over the floor during the webinar.

From the company’s European team, Head of Technical Service and Product Management, Roberto Murgioni discussed its high efficiency features stating how it is a perfect fit for rooftop projects. He showed Tiger Neo modules need fewer blocks, roof area and weight for the same volume – and the saved area also has significant positive effect on avoiding shadows shade. According to Murgioni, the manufacturer will offer high product warranties of 15-years and 25-years to the rooftop solar segment for its Tiger Neo N-type Mono facial solar panels, also available in all black variant, with highest efficiency of 21.25%.

MENA region’s Head of Technical Services for JinkoSolar, Mohamed Saady touted the module’s temperature coefficient (TC) feature that maximizes energy generation by reducing cell temperature. For the high heat region of Middle East and Africa, Saady said TOPCon modules bring less risks for hot spots ensuring more stable performance and improved efficiency. He explained that a -0.30%/°C TC of a TOPCon module results in a 3% power gain compared to a -0.35%/°C TC of a PERC module at 85 °C.

Stating TOPCon as having least possible degradation factors, JinkoSolar’s South Asia Head of Technical Services, Sai Charan Kuppili said these modules come with guaranteed high yield, enabling higher capacity utilization. “All in one cost favors TOPCon specific to manufacturing flexibility and reduced LCOE when compared with PERC and HJT,” said Kuppili.

Reiterating the same factors, Head of Technical Service at Jinko Solar Latam and Italy, Antonio Ruta argued that TOPCon modules are also well suited for utility scale facilities with their high efficiency, high power density and low temperature coefficient features as it figured in a simulation case study in Brazil. “Test run in our outdoor demonstration project shows a N-type premium energy gain in case of fixed structure up to 2.90% compared to similar PERC bifacial modules (Albedo over 25%),” explained Ruta.

Operation Director of Germany’s independent testing and certification firm TÜV Nord, Shawee Wei presented an analysis of influences on LCOE by PV modules with different technologies during the webinar and rated TOPCon higher than HJT since manufacturers find its full compatibility with PERC production line and higher theoretical efficiency as a plus.

For comparison, the TOPCon production efficiency is between 23.5% to 24.5% with theoretical efficiency of 28.2% and 28.7%, according to Wei. For HJT, production efficiency is the similar while theoretical efficiency is estimated as 27.5%, he said. As for PERC the production efficiency falls between 22.5% to 23.1% and theoretical top efficiency as 24.5%.

Panel discussion

Moderated by TaiyangNews Managing Director Michael Schmela, the panel discussion revolved around the status and future of TOPCon solar module technology.

Citing its example of starting TOPCon research way back in 2015 before launching it for mass production, JinkoSolar’s Leo Cong stressed that his company’s focus remains on improving cell technology to ensure higher module power and efficiency instead of increasing module size since that’s what the end customers desire.

TÜV Nord’s Shawee Wei believes even though TOPCon has already matured as a solar cell technology, PID risk on the front side is something to look into. However, both Wei and Prof. Dr. Robby Peibst of ISFH agreed that combined efforts from both solar PV manufacturers as well as research institutes are sure to polish it further as time goes by.

To view the recording of the presentations on the TaiyangNews YouTube channel, click here.