Chinese company Longi, a leader in the production of solar panels, announced a significant breakthrough: a record efficiency of 34.85% has been achieved for a tandem solar cell combining silicon and perovskite. This achievement surpasses the previous record of 34.6%, set by the same company in September 2024, and brings the technology closer to the theoretical limit of 35% for this type of cell.
On the edge of the theoretical limit
Achieving such high efficiency is extremely challenging, as each percentage of progress becomes increasingly difficult as you approach the theoretical limit. Most scientific sources point to 35% as the maximum efficiency for single-junction tandem silicon and perovskite cells, where each material absorbs light in different parts of the spectrum. Longi's new record, registered in the "Book of Records" of the American laboratory NREL, is proof of the extraordinary progress in this field.
Innovations in the design of the transition layer
To achieve this remarkable result, Longi researchers have introduced key innovations in the design of materials. They have developed an asymmetric molecule for the transition layer with hole conductivity, called HTL201 (hole transport layer). This new material fills the irregularities on the surface of the silicon layer with its thicker side, while the upper edge of the molecule is perfectly aligned when in contact with the perovskite.
This unique structure significantly improves the conductivity of "holes" (positive charges) and protects them from recombination with electrons, which minimizes losses from parasitic radiation. In addition, HTL201 prevents the formation of oxide films on the surface of the perovskite and silicon, which contributes to the stability and efficiency of the cell.
When tested under standard lighting conditions, Longi's 1 cm² tandem solar cell has shown:
Efficiency: 34.85%
Open circuit voltage: 2.001 V
Short circuit current density: 20.64 mA/cm²
Fill factor: 83.79%
Longi considers these results to be exceptional and hopes to apply this innovative technology to commercial solar panels in the future. This progress could lead to more efficient and cost-effective solar power generation solutions worldwide.