29.2% Efficiency Record For Tandem Solar Cell

• EPFL has announced a power conversion efficiency of 29.2% on a surface of 1 cm² for perovskite-silicon tandem solar cell
• To achieve the efficiency level, the team found enhancing perovskite crystallization process and developing highly transparent window layers as helpful
• It now believes this open the pathway to exceed 30% efficiency for the tandem using high current of silicon texture

Switzerland's public research university École Polytechnique Fédérale de Lausanne (EPFL) has reported an efficiency of 29.2% for perovskite and textured silicon tandem solar cell calling it a 'new world record' under a sub class of fully textured perovskite-silicon device. The key here is that the cell features a fully textured surface, which closely resembles that of the commercially available silicon cells.

The claim is certified by Germany's Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE).

EPFL along with Center for Electronics and Microtechnology (CSEM), previously reported 25.2% efficiency for this combination of tandem cell by superposing the 2 materials using an evaporation method and heating silicon substrate to a low temperature to crystallize a homogenous film of perovskite on silicon pyramids (see 25.2% Record For Si-Perovskite Cell).

This improvement led to 29.2% efficiency on a surface of 1 cm², which shows promise to bring down power generation costs per kWh, it explains. The team says, this opens a path to exceed 30% with the help of high current of silicon texture.

Currently, several companies and research institutes are working on silicon/tandem based solar cell solutions, and some have published new records in recent months. In March 2022, German solar research center Helmholtz-Zentrum Berlin (HZB) and Q Cells announced a 'world record' efficiency of 28.7% for a 2-terminal (2T) tandem solar cell bringing together a perovskite top cell, and a mass-production ready silicon bottom cell based on the latter's Q.ANTUM technology (see 28.7% Efficiency For 2-T Tandem Solar Cell). In November 2021, HZB researchers exceeded their previous perovskite and silicon tandem solar cell efficiency of 29.15% to report 29.80%, inching very close to breaching the 30% target they have set for themselves (see 29.80% Record Tandem Solar Cell Efficiency).

Despite all this progress, EPFL's Ballif cautions, "Several years of R&D are still needed to bring such technology and manufacturing processes to market." Adding, "A big challenge will be developing solar cells that can remain stable on our rooftops for more than 25 years. But the higher efficiency we demonstrated without changing the front texture will be very attractive for the photovoltaics industry."