TOPCon Solar Cells
TOPCon is currently the most promising solar cell design to realize carrier-selective contacts as it offers a cost-sensitive and technologically feasible evolutionary upgrade opportunity to mainstream PERC cells.
Industrial TOPCon cells are mainly based on more challenging n-type substrates, which require a boron emitter diffusion process with less industrial maturity in comparison to the POCl3 diffusion process typically used in PERC cells. Due to a higher tolerance to impurities as well as a lack of LID n-type TOPCon solar cells reveal conversion efficiencies beyond 26%.
What makes TOPCon solar cells special?
TOPCon stands for "Tunnel Oxide Passivated Contacts" and is an advancement of PERC technology. The formation of an ultra-thin tunnel oxide and the deposition of the doped poly-Si layer are the decisive process steps that are additional to the current PERC technology. The properties of these layers are vital to achieve high VOC‘s and low series resistance.
Significant improvement of cell efficiency
The ultra-thin tunnel oxide layer applied to the rear side of the cell, in combination with a highly doped silicon layer, minimizes carrier loss and improves electrical conductivity. This results in significantly higher electricity generation under the same sunlight and increases the overall efficiency beyond that of conventional PERC cells.
Reduced recombination losses through passivation
Bilateral passivation minimizes interface defects and suppresses the recombination of charge carriers, which reduces current yield.
Recombination of charge carriers between silicon and dielectric. As a result, both surface and bulk recombination processes are suppressed, leading to increased minority carrier lifetime and improved cell performance.
Improved temperature behavior
Thanks to optimized passivation and high charge carrier selectivity, TOPCon cells display a lower temperature coefficient (typically ~–0.30 %/K). This means that their performance decreases less sharply as cell temperature increases compared to conventional cell technologies, thus increasing energy yield under real operating conditions.
What role does centrotherm's process technology play?
For the production of TOPCon solar cells, we offer the most important thermal processes such as diffusion, annealing and PECVD.
