A new conversion efficiency record for a Large Area Industrial Crystalline Silicon n-PERT (passivated emitter, rear totally diffused) solar cell of 22.02% was recently achieved by the research firm Imec, as per a recent press release.
The new record efficiency — which was calibrated at ISE CalLab — represents the highest efficiency achieved by this type of 2-side-contacted solar cell on an industrial large area wafer size, to date.
Said solar cell, manufactured via a 6” commercially available n-type Cz-Si wafers, represents a notable improvement over previous designs across a number of parameters — and brings the wide-scale commercial use of the type closer.
With regard to the inherent advantages of n-type solar cells over p-type silicon solar cells, n-type cells aren’t affected to the same degree by light-induced degradation, and they also possess a higher tolerance to common metal impurities. Owing to those qualities, n-type cells are considered by many to be a promising technology.
“Our new developments, resulting in additional improvement of the conversion efficiency, further confirm the potential of n-type PERT cells for next-generation highly efficient silicon solar cells,” stated Filip Duerinckx, manager of imec’s n-PERT technology platform. “This new efficiency record has been achieved while simultaneously simplifying the process, relying only on simplified cleans and without any expensive Forming Gas Anneal (FGA). We are committed to further increasing the efficiency of this cell concept and adding to the industrial value of the technology. This will enable bringing this technology to the market in short term.”
Here are some of the technical specifics:
Looking into increasing the conversion efficiency of its large-area n-PERT silicon cells using advanced industrial-processes, imec has further improved the conversion efficiency of its n-PERT solar cell, reaching a record 22%, featuring an open-circuit voltage (Voc) of 684mV, a short-circuit current (Jsc) of 39.9 mA/cm2, and 80.7% fill factor (FF). Efficiency improvements were obtained by the introduction of a selective front surface field through laser doping, giving a boost in open circuit voltage and short circuit current.
Imec’s n-PERT silicon solar cells feature Ni/Cu/Ag front contacts, applied using an industrial plating tool from Meco, and rear local contacts obtained by laser ablation of the rear passivation stack and subsequent metallization. The rear passivation stack includes a thin (<10 nm) Atomic-Layer-Deposited (ALD) Al2O3 layer, deposited with the spatial ALD technique InPassion Lab® from SoLayTec. The diffused Front Surface Field (FSF) and rear emitter as well as the Anti-Reflective Coating (ARC) are applied in a Tempress batch-type furnace.
Another promising development for sure, but technical improvements and economical deployment are two very different things. Until the approach is shown to be commercially economical, it will remain a technical curiosity, of course, no more.
Image Credit: Imec
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