Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Perovskites provide big boost to silicon solar cells, Stanford study finds


Stacking perovskites onto a conventional silicon solar cell dramatically improves the overall efficiency of the cell, according to a new study led by Stanford University scientists.

The researchers describe their novel perovskite-silicon solar cell in this week's edition of the journal Energy & Environmental Science.

This is a microscopic cross-section of a tandem solar cell made with two photovoltaic materials, perovskite and copper indium gallium diselenide, or CIGS.

Credit: Colin Bailie, Stanford University

"We've been looking for ways to make solar panels that are more efficient and lower cost," said study co-author Michael McGehee, a professor of materials science and engineering at Stanford. "Right now, silicon solar cells dominate the world market, but the power conversion efficiency of silicon photovoltaics has been stuck at 25 percent for 15 years."

One cost-effective way to improve efficiency is to build a tandem device made of silicon and another inexpensive photovoltaic material, he said.

"Making low-cost tandems is very desirable," McGehee said. "You simply put one solar cell on top of the other, and you get more efficiency than either could do by itself. From a commercial standpoint, it makes a lot of sense to use silicon for the bottom cell. Until recently, we didn't have a good material for the top cell, then pervoskites came along."

Perovskite is a crystalline material that is inexpensive and easy to produce in the lab. In 2009, scientists showed that perovskites made of lead, iodide and methylammonium could convert sunlight into electricity with an efficiency of 3.8 percent. Since then, researchers have achieved perovskite efficiencies above 20 percent, rivaling commercially available silicon solar cells and spawning widespread interest among silicon manufacturers.

"Our goal is to leverage the silicon factories that already exist around the world," said Stanford graduate student Colin Bailie, co-lead author of the study. "With tandem solar cells, you don't need a billion-dollar capital expenditure to build a new factory. Instead, you can start with a silicon module and add a layer of perovskite at relatively low cost."

Sunlight to electricity

Solar cells work by converting photons of sunlight into an electric current that moves between two electrodes. Silicon solar cells generate electricity by absorbing photons of visible and infrared light, while perovskite cells harvest only the visible part of the solar spectrum where the photons have more energy.

"Absorbing the high-energy part of the spectrum allows perovskite solar cells to generate more power per photon of visible light than silicon cells," Bailie said.

A key roadblock to building an efficient perovskite-silicon tandem has been a lack of transparency.

"Colin had to figure out how to put a transparent electrode on the top so that some photons could penetrate the perovskite layer and be absorbed by the silicon at the bottom," McGehee said. "No one had ever made a perovskite solar cell with two transparent electrodes."

Perovskites are easily damaged by heat and readily dissolve in water. This inherent instability ruled out virtually all of the conventional techniques for applying electrodes onto the perovoskite solar cell, so Bailie did it manually.

"We used a sheet of plastic with silver nanowires on it," he said. "Then we built a tool that uses pressure to transfer the nanowires onto the perovskite cell, kind of like a temporary tattoo. You just need to rub it to transfer the film."

Remarkable efficiency

For the experiment, the Stanford team stacked a perovskite solar cell with an efficiency of a 12.7 percent on top of a low-quality silicon cell with an efficiency of just 11.4 percent.

"By combining two cells with approximately the same efficiency, you can get a very large efficiency boost," Bailie said.

The results were impressive.

"We improved the 11.4 percent silicon cell to 17 percent as a tandem, a remarkable relative efficiency increase of nearly 50 percent," McGehee said. "Such a drastic improvement in efficiency has the potential to redefine the commercial viability of low-quality silicon."

In another experiment, the research team replaced the silicon solar cell with a cell made of copper indium gallium diselenide (CIGS). The researchers stacked a 12.7 percent efficiency perovskite cell onto a CIGS cell with a 17 percent efficiency. The resulting tandem achieved an overall conversion efficiency of 18.6 percent.

"Since most, if not all, of the layers in a perovskite cell can be deposited from solution, it might be possible to upgrade conventional solar cells into higher-performing tandems with little increase in cost," the authors wrote.

A big unanswered question is the long-term stability of perovskites, McGehee added.

"Silicon is a rock," he said. "You can heat it to about 600 degrees Fahrenheit shine light on it for 25 years and nothing will happen. But if you expose perovskite to water or light it likely will degrade. We have a ways to go to show that perovskite solar cells are stable enough to last 25 years. My vision is that some day we'll be able to get low-cost tandems that are 25 percent efficient. That's what companies are excited about. In five to 10 years, we could even reach 30 percent efficiency."

The study was also written by co-lead author M. Greyson Christoforo, Andrea Bowring, Eva Unger, William Nguyen and Alberto Salleo from Stanford; Jonathan Mailoa, Jungwoo Lee and Tonio Buonassisi from the Massachusetts Institute of Technology; Julian Burschka, Norman Pellet and Michael Graetzel from the Swiss École Polytechnique Fédérale de Lausanne; and Rommel Noufi, formerly with the U.S. National Renewable Energy Laboratory.

This article was written by Mark Shwartz, Precourt Institute for Energy at Stanford University.

Media Contact

Mark Shwartz


Mark Shwartz | EurekAlert!

More articles from Power and Electrical Engineering:

nachricht Solid progress in carbon capture
27.10.2016 | King Abdullah University of Science & Technology (KAUST)

nachricht Greater Range and Longer Lifetime
26.10.2016 | Technologie Lizenz-Büro (TLB) der Baden-Württembergischen Hochschulen GmbH

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

'Neighbor maps' reveal the genome's 3-D shape

27.10.2016 | Life Sciences

Gene therapy shows promise for treating Niemann-Pick disease type C1

27.10.2016 | Life Sciences

Solid progress in carbon capture

27.10.2016 | Power and Electrical Engineering

More VideoLinks >>>