Perovskite solar cells surpass 20 percent efficiency

June 09, 2016

EPFL researchers are pushing the limits of perovskite solar cell performance by exploring the best way to grow these crystals.

Michael Graetzel and his team found that, by briefly reducing the pressure while fabricating perovskite crystals, they were able to achieve the highest performance ever measured for larger-size perovskite solar cells, reaching over 20% efficiency and matching the performance of conventional thin-film solar cells of similar sizes. Their results are published in Science.

This is promising news for perovskite technology that is already low cost and under industrial development.

However, high performance in pervoskites does not necessarily herald the doom of silicon-based solar technology. Safety issues still need to be addressed regarding the lead content of current perovskite solar-cell prototypes in addition to determining the stability of actual devices.

Layering perovskites on top of silicon to make hybrid solar panels may actually boost the silicon solar-cell industry. Efficiency could exceed 30%, with the theoretical limit being around 44%. The improved performance would come from harnessing more solar energy: the higher energy light would be absorbed by the perovskite top layer, while lower energy sunlight passing through the perovskite would be absorbed by the silicon layer.

From dye solar cells to perovskite

Graetzel is known for his transparent dye-sensitized solar cells. It turns out that the first perovskite solar cells were dye-sensitized cells where the dye was replaced by small perovskite particles.

His lab's latest perovskite prototype, roughly the size of an SD card, looks like a piece of glass that is darkened on one side by a thin film of perovskite. Unlike the transparent dye-sensitized cells, the perovskite solar cell is opaque.

How to make a perovskite solar cell

To make a perovskite solar cell, the scientists must grow crystals that have a special structure, called "perovskite" after Russian mineralogist Lev Perovski who discovered it.

The scientists first dissolve a selection of compounds in a liquid to make some "ink". They then place the ink on a special type of glass that can conduct electricity. The ink dries up, leaving behind a thin film that crystallizes on top of the glass when mild heat is applied. The end result is a thin layer of perovskite crystals.

The tricky part is growing a thin film of perovskite crystals so that the resulting solar cell absorbs a maximum amount of light. Scientists are constantly looking for smooth and regular layers of perovskite with large crystal grain size in order to increase photovoltaic yields.

For instance, spinning the cell when the ink is still wet flattens the ink and wicks off some of the excess liquid, leading to more regular films. A new vacuum flash technique used by Graetzel and his team also selectively removes the volatile component of this excess liquid. At the same time, the burst of vacuum flash creates seeds for crystal formation, leading to very regular and shiny perovskite crystals of high electronic quality.
-end-


Ecole Polytechnique Fédérale de Lausanne

Related Glass Articles from Brightsurf:

Glass tables can cause life-threatening injuries
Faulty glass in tables can cause life-threatening injuries, according to a Rutgers study, which provides evidence that stricter federal regulations are needed to protect consumers.

The nature of glass-forming liquids is more clear
Researchers from The University of Tokyo have found that attractive and repulsive interactions between particles are both essential to form structural order that controls the dynamics of glass-forming liquids.

Experimental study of how 'metallic glass' forms challenges paradigm in glass research
Unlike in a crystal, the atoms in a metallic glass are not ordered when the liquid solidifies.

On-demand glass is right around the corner
A research group coordinated by physicists of the University of Trento was able to probe internal stress in colloidal glasses, a crucial step to control the mechanical properties of glasses.

Glass from a 3D printer
ETH researchers used a 3D printing process to produce complex and highly porous glass objects.

Making glass more clear
Northwestern University researchers have developed an algorithm that makes it possible to design glassy materials with dynamic properties and predict their continually changing behaviors.

Researchers use 3D printer to print glass
For the first time, researchers have successfully 3D printed chalcogenide glass, a unique material used to make optical components that operate at mid-infrared wavelengths.

New family of glass good for lenses
A new composition of germanosilicate glass created by adding zinc oxide has properties good for lens applications, according to Penn State researchers.

In-depth insights into glass corrosion
Silicate glass has many applications, including the use as a nuclear waste form to immobilize radioactive elements from spent fuel.

New research questions the 'Glass Cliff' and corroborates the persistent 'Glass Ceiling'
Are women more likely to be appointed to leadership positions in crisis situations when companies are struggling with declining profits?

Read More: Glass News and Glass Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.