Solar cells boosted to 20.8% efficiency

When it comes to solar cells, cost and efficiency are key factors for moving from the lab to the market. Metal-halide perovskites show outstanding photovoltaic properties combined with relatively cheaper manufacturing. Consequently perovskites have drawn much research attention in recent years. EPFL scientists have now developed a new perovskite-based photovoltaic cell that shows an unprecedented 20.8% light-to-electricity conversion efficiency. The study is published in Science Advances.

The labs of Anders Hagfeldt and Michael Grätzel at EPFL focused their world-renowned expertise in photovoltaic materials on organo-lead-halide perovskites. These materials entered the solar-cell world about five years ago as promising candidates for efficient and cost-effective solar power.

Led by Dongqin Bi and Wolfgang Tress (Hagfeldt’s and Grätzel’s labs respectively), a team of researchers tuned the composition of an organo-lead-halide perovskite used as a light absorber. The material was deposited on the solar cell in a single step as a nano-crystalline film from a solution. Potentially, this represents a much cheaper method for fabricating these cells than conventional approaches.

The researchers were able to fine-tune the material’s composition until a version with an excess of lead halide achieved 20.8% power conversion efficiency, combined with a remarkably high photovoltage (1.18 V). These values approach the theoretical limits set by the field for these types of solar cells.

The perovskite material exhibited high electronic quality allowing for intense electroluminescence. Because of suppressed non-radiative recombination losses, the electroluminescence yield (quantum efficiency) it reached matched the emission of the best silicon solar cells in the market - but all the while using deposition methods compatible with low-cost manufacturing.

The authors state that this achievement will pave the way for solution-processed high-voltage solar cells, but they expect that it will also extend to light-emitting devices for various technological applications.

This study involved a collaboration between EPFL’s Laboratory of Photomolecular Science, Laboratory of Photonics and Interfaces, and Group for Molecular Engineering of Functional Materials. It was funded by the European Union Seventh Framework Program (including the MESO, NANOMATCELL, and Powerweave projects
), the Swiss National Science Foundation, and CCEM-CH.

Reference

Bi D, Tress W, Dar MI, Gao P, Luo J, Renevier C, Schenk K, Abate A, Giordano F, Correa Baena J-P, Decoppet J-D, Zakeeruddin SM, Nazeeruddin MK, Grätzel M, Hagfeldt A, Efficient luminescent solar cells based on tailored mixed-cation perovskites.Science Advances 2, e1501170 (2016). DOI: 10.1126/sciadv.1501170