23.2% Efficiency For Bifacial N-PERT Solar Cells

• Imec has announced 23.2% front side conversion efficiency for its n-PERT solar cells developed with Jolywood
• Out of a batch of 12 new M2-sized solar cells of 2 cm² measured at ISFH CalTec, the best cell topped 23.2% efficiency, as the rest achieved efficiency of 23%
• For the research, the team optimized fully screenprinted bifacial n-PERT cell process and adopted a design with 12 busbars
• The cells used also have a screenprinted front grid and rear soldering pads that use less silver
• The 2 collaborating partners now aim for bifacial n-PERT cells conversion efficiency of above 23.5% coupled with a bifaciality of over 90%

Belgium located technology research institute imec has announced a 23.2% front-side conversion efficiency for its n-PERT (Passivated Emitter and Rear Totally Diffused) solar cells developed with China's Jolywood. Imec says n-PERT cells have the potential for high efficiencies because of lower sensitivity to metal impurities and the absence of light induced degradation (LID), which makes these a serious and cost-effective contender to p-type PERC cells.

The experiment was conducted on a batch of 12 new M2-sized cells of 244.2 cm² measured at ISFH CalTec, which showed conversion efficiencies of 23%, with the best cell topping 23.2%. Imec says its own measurements showed a bifaciality of above 80%, while claiming the cells can achieve an effective conversion efficiency of almost 26% when used under standard front illumination conditions in conjunction with an additional 0.15 sun rear illumination.

"Compared to the previous results imec reported, we have further optimized the fully screenprinted bifacial n-PERT cell process and adopted a design with 12 busbars. The current cells also have a screenprinted front grid and rear soldering pads that use less silver," said Loic Tous, project leader at imec/EnergyVille. "The open circuit voltage (Voc) is now above 690 mV with fill factors up to 83%. These remarkable results are obtained using the same industry-compatible equipment to produce bifacial p-PERC cells, with the addition of a boron diffusion."

Both imec and Jolywood are now aiming for bifacial n-PERT cells conversion efficiency of above 23.5%, coupled with a bifaciality of above 90%.

In September 2018, imec reported 23.03% conversion efficiency for n-PERT cells on its pilot line while sharing a technology roadmap for the efficiency to eventually surpass 24% (see Higher Efficiency For Imec's nPERT & Tandem CIGS Cell).