A team from the School of Modern Engineering and Applied Sciences, Nanjing University, China, has raised the efficiency of tandem all-perovskite triple-junction solar cells to over 30%. They explain that single-junction solar cells can only absorb sunlight through a single bandgap: photons with energy below the bandgap cannot be absorbed, while the energy above the bandgap is lost as heat. Multijunction cells utilise the solar spectrum in segments by stacking sub-cells with different bandgaps, thereby gradually reducing these losses.

All-perovskite trijunction cells consist of three layers of thin-film semiconductors with adjustable bandgap, offering broad spectral utilisation, low-temperature fabrication and compatibility with lightweight flexible substrates. The researchers found ways to overcome two major problems in making these, preventing them from wrinkling during production and stopping key elements from clumping together. The work was published in Nature Energy on 10 September.

Meanwhile, researchers at Soochow University in Taipei, Taiwan, have developed a perovskite/silicon tandem solar cell that reached a laboratory power conversion efficiency of 34%. Perovskite/silicon tandem solar cells combine a wide-bandgap perovskite top cell with a silicon bottom cell to use sunlight more efficiently than conventional single-junction silicon cells. Their performance, however, is limited by uneven perovskite growth on textured silicon. The researchers inserted another layer of insulating zirconia nanoparticles in between the two, which improved the panel’s function.

In June, the Fraunhofer Institute for Solar Energy Systems ISE announced a III-V germanium photovoltaic (PV) module that achieves an efficiency of 34.4%. That module had a 34.2% efficiency, but was improved with a new connection method, in collaboration with a mechanical engineering partner.

The shingle-matrix approach represents a fundamental departure from traditional PV module construction, in which solar cells are cut into narrow strips and then arranged in a shingle-like pattern – overlapping and offset from one another – and connected using electrically conductive adhesives. This architecture enables direct cell-to-cell contact, thereby eliminating the need for traditional solder-coated copper ribbons. The key advantage: by eliminating cell interconnects, no active cell area is shaded.

The solar cells were made by Azur Space Solar Power and anti-reflective coatings on the front glass were provided by Temicon.