A team of researchers from LONGi, a Chinese module manufacturer, and the School of Materials at Sun Yat-sen University have successfully created heterojunction (HJT) back contact solar cells with an impressive power conversion efficiency of 27.09%.
The findings of the experiments, which have been published in the journal Nature, highlight that most of the recombination losses originate from the “hole-selective contact region” and “polarity boundaries.” The researchers suggest novel manufacturing techniques to mitigate these losses and enhance the overall efficiency of the solar cells.
The team of researchers conducted a comprehensive evaluation of a ten-step cell production process. This process involved various stages such as wet chemical cleaning, chemical vapor deposition on the rear side of the cells, and the utilization of laser patterning. The tests were performed at LONGi’s commercial HJT back contact (HBC) production line, which is responsible for manufacturing the company’s M6-sized modules.
Additionally, the research study explored the substitution of “amorphous silicon layers” in the cells with “nanocrystalline-doped films” that act as transport layers. The researchers discovered that this modification significantly enhanced the power conversion efficiency of the solar cell. In the abstract of the study, the authors highlight that incorporating nanocrystalline structures in the transport layers has the potential to achieve a power conversion efficiency as high as 27.7%.
The authors of the report explained in their study that when compared to nanocrystalline silicon, amorphous silicon has limitations in suppressing charge carrier transport loss. This inefficiency arises from inadequate transport at the interface between the doped layer and the transparent conductive oxide layer, which hinders the band-to-band tunneling mechanism based on direct energy transitions. To enhance the efficiency of the solar cells, the authors recommend the adoption of nanocrystalline silicon technology to improve the contact properties.
The Institute for Solar Energy Research in Hamelin, Germany, independently verified the results of the study. The successful testing of these processes at a commercial-scale facility holds the potential to expedite the implementation and scaling up of these methods in the solar industry.
This development comes on the heels of LONGi’s introduction of a back contact module earlier this year, boasting a power conversion efficiency of 22.3%. Additionally, the company recently unveiled the Hi-MO X10 module, which also utilizes LONGi’s hybrid passivated back contact (HBPC) cells. These product launches signify LONGi’s ongoing commitment to advancing research in back contact technology.
