The new laser manufacturing process may promote a complete change in the photovoltaic market

The Solar Systems Institute in Freiburg, Germany, has developed a laser-based manufacturing process approach that is revolutionizing the photovoltaic market
.
For the first time, point-contact solar cells can be mass-produced
.
Millions of batteries with high efficiency levels have already entered the market
.

One of the major challenges facing our society in the coming decades is that our energy system aims to
produce more electricity from renewable sources.
Solar technology plays a decisive role
in achieving this goal.
"The total amount of electricity produced from photovoltaic energy exceeds 250 terawatt hours, which is roughly equivalent to the electricity
produced by 30 nuclear power plants.
In order to meet the international climate change goals, photovoltaic power generation capacity will be added every year, and in the next 15 years, it will increase tenfold
.
In general, in order to meet the demands of the electricity market, solar technology must become more efficient and cost-effective," says Dr.
Ralf Preu, Director of the Photovoltaic Production Technology and Quality Assurance Department at the Solar System Institute Freiburg, Germany
.
Dr.
Ralf Preu and his colleague Dr.
Jan Nekarda have made significant contributions to the development of laser sintering (LFC) technology, enabling the production of more efficient solar cells
at a lower cost.

Today, most solar cells are equipped with a wide metal contact layer that covers the back of the silicon wafer, allowing current to flow from the solar cell to the electrodes
.
This configuration leads to inefficiencies
.
A more efficient alternative, the passivation emitter back-contact (PERC) solar cell technology
, was developed in 1989.
In contrast to conventional battery technology, this technology includes a back-reflective layer of solar cells and thousands of electrical contact points
.
The LFC process developed by researchers at the German Solar System Institute enables the first large-scale industrial production
of PERC solar cells.

Mass production of high-efficiency batteries

A very thin non-conductive layer covers the bottom of the PERC solar cell, between
the metal contact layer and the wafer.
As a reflector, when sunlight hits the silicon wafer, this non-conductive layer reflects some of the sunlight instead of absorbing all of it
.
Since the front of the cell also reflects light onto the wafer, the silicon wafer can also capture sunlight, increasing the efficiency level of the solar cell
.
Deriving current from the wafer requires many small holes in the non-conductive layer to allow the metal electrode to come into contact
with the silicon wafer.
The LFC process enables nearly 100,000 contact points on the wafer, each of which must be connected
to a single laser pulse.
The biggest difficulty in this work is that the laser pulse can form good contact with the silicon surface, reducing damage
to the material.
The most important point is that the laser's action is limited to between 50 and 2,000 nanoseconds, explains
Dr.
Jan Nekarda.
The innovative system they developed guides the laser beam so that it optimizes the energy density distribution
in close to 1 second.

"PERC solar cells use this method to increase the efficiency level
by 1% absolute value.
Based on today's conversion efficiency of nearly 20% for solar cells, this is equivalent to a relative value
of about 5%.
Our additional 2% increase in the system means that we have increased our total energy output by 7%," said
Dr.
Ralf Preu.
The level of efficiency is critical because the vast majority of PV costs are proportional
to the surface area.
"Today we need 100 square meters of solar cells, so in the future we will only need 93 square meters to generate the same amount of electricity
.
This not only means less silicon use, but also less module material, which reduces costs in the system.
"

Success in the industrial sector

Solar cell manufacturers can easily and cost-effectively integrate laser processes into existing production processes
.
According to company information, Hanwha Q Solar Cell Company has produced 20 million cells
using LFC technology.
Many companies around the world have put PERC technology into mass production
.
"This year alone, manufacturers have invested 200 million euros to implement this technology
.
This means that silicon solar cells have entered the next revolutionary phase," Ralf Preu said
excitedly.

Ralf Preu and Jan Nekarda have received the 2016 Joseph von Fraun Prize for their status
as initiators and drivers of change in solar technology.
The jury attributed their award to "the technology developed by the researchers helps German companies continue to succeed in
the highly competitive PV market.
" ”