The technological race in the field of renewable energy has reached a new turning point thanks to the latest achievements of the Chinese company LONGi. The Asian leader announced a new world record for the efficiency of a classic single-junction silicon solar cell. The impressive result of 28.29% conversion of sunlight into electricity was officially confirmed by independent tests at the German Institute for Solar Energy Research in Hameln (ISFH), bringing the photovoltaic industry very close to the theoretical maximum for this type of architecture.
The basis of the record achievement is the innovative HIBC (Hybrid Interdigitated Back Contact) architecture, in which the contact paths are completely on the back of the panels. Unlike bulk solar cells, where metal conductors partially cover the front surface and block part of the light flux, the back-contact design frees up the entire front surface for light absorption. This approach reduces carrier recombination losses and optimizes photon reception.
The cell core consists of a high-resistivity silicon wafer with a standard M10 format (182 x 182 mm), combined with advanced edge passivation technologies and optimized n-junctions. To improve charge transfer, engineers have relied on a layer of indium tin oxide (ITO), while multilayer coatings of aluminum oxide (AlOx) and silicon nitride (SiNx) ensure strong suppression of surface recombination. The phosphorus concentration in the n-type polycrystalline layer has been further reduced to prevent unwanted diffusion of impurities into the pure silicon.
To achieve an optimally low contact resistance without compromising the passivation properties, the research team applied precision laser processing with a pulsed green nanosecond laser. This technology allows for partial crystallization of the amorphous silicon layer with microscopic precision. LONGi emphasizes that the HIBC technology has full potential for mass industrial production in heterojunction cells, although future yield increases will require strict optimization of ohmic losses in the p-region.
The company's calculations show that today's silicon cells have already utilized approximately 96.2% of their theoretical limit, making further improvements extremely difficult and dependent on microscopic tuning of the materials. The record-breaking 28.29% is the culmination of a string of successes throughout the year, which included consecutive achievements of 28.04% and 28.13%. In parallel, the company is already working on the next generation of tandem silicon-perovskite cells, where the bar has already passed the 34.6% efficiency mark.