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Science, 2022, 378, 6626, 1295-1300 | Published 12/22/2022

This recent collaborative report, published in Science, brings together researchers from the National Renewable Energy Laboratory (NREL), University of Colorado Boulder (¶¶ÒõÂÃÐÐÉä Boulder) and the University of Toledo, and includes RASEI Fellows Matthew Beard and Joseph Berry.

Tandem perovskite solar cells hold huge promise for future harvesting of solar energy. This work describes a new approach that greatly improves the reliability and robustness of technologies based on these materials.

Mixed halide perovskites, which contain a mixture of both iodine and bromine, are much more effective at capturing the sun’s energy than perovskites that contain just iodine or bromine. However, when these are repeatedly heated and cooled (as is required if you are going to install these on your roof), the bromine and iodine separate, which significantly reduces the efficiency of these materials. One of the identified causes of this separation is the presence of defects in the perovskite – essentially errors in the way in which the perovskite is stacked.

This report describes a new method that reduces the number of errors in the way the perovskites are built, which helps prevent the iodine and bromine separation, producing much more stable solar cells. Using a technique known as gentle gas quenching allows scientists to create perovskite films with far fewer defects, that have excellent operational stability. Using this new technique the team produced all-perovskite solar cells with 27.1% efficiencies.

ACS Energy Letters, 2022, 7, 12, 4265-4273 | Published 11/02/2022

An international and interdisciplinary team, including RASEI members Seth Marder and Stephen Barlow, report on how the addition a cheap and readily available commodity chemical improves the performance and materials stability of perovskite materials.

This team, that brings together researchers from ¶¶ÒõÂÃÐÐÉä Boulder, the University of Washington, and the University of Oxford (UK), explored another approach to preventing defect formation in perovskites. As perovskite films are constructed, known as crystallization, errors and defects can creep in. The addition of ethylenediamine, an extremely cheap and readily available chemical, modulates the crystallization of the perovskites, which reduces the number of errors in its structure.

Employing the more regular and reliable perovskite structures not only improves the performance and stability of the perovskites in harvesting solar energy, it also provides possibilities for a more reproducible and scalable approach, critical for the application of these materials in real world installations.

ACS Energy Letters, 2023, 8, 898-900 | Published 01/06/2023

Research around perovskite materials has made huge strides in the past decade toward integration into commercial solar cells, but we are not there, yet. This team, which includes RASEI Fellow Mike McGehee, and researchers from the Kaunas University of Technology in Lithuania, and the Helmholtz Zentrum Berlin in Germany, report their work on one of the hurdles that has recently been identified for the reliable manufacture of perovskite-based solar cells.

In the repeated manufacture of perovskite devices in the lab setting it has been observed that the creation of a layer of perovskites has low reproducibility, sometimes it works extremely well, and sometimes the cell is terrible. This report provides evidence that this is due to the nonpolar nature of the surface. In the same way that water on an oily surface doesn’t form a uniform layer and instead forms droplets, the perovskite solution does the same thing.

The team showed that introduction of a polar molecule into the surface made it less ‘greasy’, and the polar perovskite solution made a thin film instead of droplet. This led to the formation of a reliable, reproducible and well covered perovskite solar cells, which showed high energy conversion efficiencies.