Structured silicon perovskite from EPFL approaches 30% efficiency for tandem solar cells

Scientists from the Swiss Federal Institute of Technology in Lausanne have created a high-efficiency tandem solar cell based on industrial p-type crystalline silicon. It represents an intermediate step towards yields above 30%.


New world record for structured perovskite-silicon photovoltaics

New records have been reached in the field of tandem photovoltaics. Researchers from the Federal Polytechnic School of Lausanne (EPFL) have a new milestone on the road to commercialization of perovskite-silicon solar cells.

For some time now, photovoltaic research has focused on this mixture of materials with the aim of market products with yields greater than 30%.

Standard silicon absorbs low-energy photons, while perovskite is the ideal material for harnessing high-energy blue photons. Combining these two semiconductors means expanding the part of the usable light spectrum and, therefore, the overall performance.

In practice, however, there are still a number of technical issues. One of the hurdles to overcome is how to evenly cover the surface of crystalline silicon with a thin film of perovskite.

This is because the surface of crystalline silicon is industrially produced to be uniformly rough (or textured) for the specific purpose of reducing reflections. This hinders the growth of perovskite crystals.

But scientists at EPFL’s Photovoltaic and Thin-film Electronics Laboratory (PV-lab), directed by Christophe Ballif, have found a way around the obstacle. And in 2018, they created the first structured perovskite-silicon cell with an efficiency of 25.2%.

Today, researchers are raising the bar again. Thanks to the improvement of the perovskite crystallization process and the development of highly transparent “window layers”, they achieved cells of one square centimeter with an efficiency of 29.2%. A record value for this segment, independently certified by the Fraunhofer ISE.

But for the team, this is only an intermediate step towards the real goal: to create a cell structured in tandem of perovskite and silicon with an efficiency greater than 30%.

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