Methodologies based on perovskite crystals have great potential for photovoltaics
By Gary Elinoff,
Speaking at a session of the EuroNanoForum conference in
Malta, Artur Kupczunas of Saule Technologies described his company’s efforts to
produce solar panels an order of magnitude
thinner than human hair by exploiting perovskite crystals. The
technique is not only far cheaper than conventional silicon-based cells, but
also has the advantage of being printable on a wide range of surfaces, including
present-day smartphone surfaces.
However, problems remain, with atmospheric oxygen and
humidity being the chief culprits. While efficiencies of 31% are potentially
achievable and lab-based presentations of 22% have been demonstrated, stability
is a major barrier to commercialization. The solar cells built so far using
perovskites just can’t stand up to real-world conditions that must be endured
outside the protected environment of a research lab.
What are perovskite crystals?
These materials were originally discovered in Russia’s Ural
Mountains in the 19th century and named after the Russian
minerologist L.A. Perovki. The basic chemical formula is ABC3,
with A and B being two cations and C being the anion that binds them, and they
can be fabricated using techniques well familiar to manufacturers of thin-film
silicon solar cells.
Steps toward practicality
Recently, as reported in ScienceAlert, a group
at the Ecole
Polytechnique Fédérale de Lausanne (EFPL) in Switzerland has produced a solar cell
that can survive in the real-world environment and produce electricity from
sunlight at an efficiency of 11.2%. In
collaboration between Mohammad Khaja
Nazeeruddin’s group at EPFL, Michael Grätzel, also of EPFL, and the Solaronix
Corporation, the effort employed two different types of nanoparticles; 2D and 3D
perovskite, with the former providing insulation against oxygen and water, and
the latter providing the electricity.
Perovskite solar cell. Source: Ecole Polytechnique Fédérale de Lausanne (edited).
laboratory-based example, both types of perovskites were synthesized using the
ordinary means of wet chemistry. The complete 2D/3D solar cell was built,
sandwich-like, by orienting the two variations of perovskites on top of each
other, as illustrated above.
Grätzel, who before
this project produced a perovskite solar cell that hit 15% sunlight conversion
efficiency in the lab, noted last year in the MIT
that “The material is dirt cheap.” And, as noted by Solaronix, another of the partners in the
enterprise with long-term experience in nano-particle synthesis and the
printing of nano-inks, less than a gram of the perovskite material is enough to
generate electricity over an entire square-meter solar cell.