As the global solar PV industry looks beyond Passivated Emitter and Rear Cell (PERC) solar cell technology, more or less they see Passivated Contact Cells, also called TOPCon, as a worthy contender. By the way things stand, an abbreviation of Tunnel Oxide Passivated Contacts, TOPCon stands in line to take over from PERC in a smooth transition, but then heterojunction (HJT) could pose a challenge.
This was the topic of discussion during day 3 of TaiyangNews High Efficiency Solar Technologies virtual conference with the executive panel offering their insights on TOPCon-An Easy PERC Upgrade Towards Higher Efficiencies in a session moderated by TaiyangNews Head of Technology Shravan Chunduri.
From the manufacturing point of view, Jolywood's Vice General Manager Dr. Liu Zhifeng said he would prefer N-type TOPCon any day for the ease with which it can be integrated into current production equipment used for PERC with a few tweaks. This means huge savings in cost while HJT is more expensive because it requires investment in completely different equipment.
Currently, according to Zhifeng, the capex for TOPCon on a GW scale translates into $30 million for 1 GW, 15% higher than P-PERC. Jolyood is already a leader in TOPCon with 2 GW capacity today. Zhifeng shared that in 2021, Jolywood's TOPCon production capacity will be at least 3 GW and could exceed that. While Jolywood has been relying on a LPCVD and ion-implantation based route to produce TOPCon cells, the company has now developed a so called J-TOPCon 2.0 technology using plasma oxidation and plasma assisted in-situ doping Deposition (POPAID). The technology has been implemented in its pilot line. Jolyowood, a pioneer in TOPCon cell/module production, reached efficiencies of around 22% in 2018, which it increased to nearly 23.9% in 2020, with a roadmap to 25.5% in mass production by 2025.
Fraunhofer ISE's Head of Department Production Technologies Dr. Jochen Rentsch agreed that TOPCon makes sense as an upgrade for the current mainstream technology since PERC has over 150 GW production capacity in operation, which offers both a financial and technological logic. But he believes that if a manufacturer considers a big upgrade, then HJT would be the better choice even though it is much more difficult to manage, also regarding bigger wafer based modules, which is the current trend with PERC. TOPCon that way works as well as PERC. Rentsch showed that TOPCon cells processed using PECVD simplifies the process to 8 steps and attained 23% efficiency.
Leading wet chemical supplier for the PV manufacturing industry RENA Technologies' Technology & Process Director Dr. Holger Kuhnlein said the market is quite excited about HJT and he can see more of it coming up in the near future, but since TOPCon is similar to PERC, metallization is not much of a challenge here. HJT in comparison offers high efficiency but is more delicate to deal with. And of course, with cost considerations, it still takes time before HJT can go the TOPCon way. In his talk, Kuhnlein summarized the range of wet-chemical solutions offered by RENA for various cell structures. For example, for passivated contacts, RENA is offering a fitting plating solution called InCellPlate for metallization of TOPCon cells and In(Ox)PolySide for removing the wrap-around, a common side effect of polysilicon deposition.
The detailed agenda of TaiyangNews' High Efficiency Solar Technologies conference is available on our website. Day 1 of the conference on Dec. 1, 2020 was dedicated to 182 mm high efficiency solar modules based on today's incumbent PERC technology (see Day 1: TaiyangNews High Efficiency Solar Event). Day 2 focused on heterojunction technology and on the occasion TaiyangNews launched the 2nd edition of Heterojunction Solar Technology Report 2020 (see Day 2: TaiyangNews High Efficiency Solar Event).
Recordings of the presentations shared during the conference are now available for online viewing on TaiyangNews' You Tube Channel.