Info
Info
News Article

Sheets Of Stapled Semiconductors Could Make Ultra Thin Solar Cells

Researchers combine tungsten diselenide with molybdenum disulphide to create 'designer' optoelectronic material

Researchers at the Vienna University of Technology have used two ultra-thin layers to create a new semiconductor structure suited for photovoltaic energy conversion.

Several months ago, Marco Furchi, Thomas Mueller, and Andreas Pospischil (pictured l-r) produced an ultra-thin layer of the photoactive crystal tungsten diselenide. Now, they have combined this semiconductor with another layer made of molybdenum disulphide, creating a material that shows potential for a new kind of solar cell technology, they say,  that is extremely thin, semi-transparent, and flexible.

Two layers with different functions

Tungsten diselenide is a semiconductor which consists of three atomic layers. One layer of tungsten is sandwiched between two layers of selenium atoms. (The image shows the two semiconductor layers in the middle, connected to electrodes on either side).

When light shines on a photoactive material single electrons are removed from their original position. A positively charged hole remains, where the electron used to be. Both the electron and the hole can move freely in the material, but they only contribute to the electrical current when they are kept apart so that they cannot recombine.

To prevent recombination of electrons and holes, metallic electrodes can be used, through which the charge is sucked away - or a second material is added. "The holes move inside the tungsten diselenide layer, the electrons, on the other hand, migrate into the molybednium disulphide", says Mueller. Thus, recombination is suppressed.

This is only possible if the energies of the electrons in both layers are tuned exactly the right way. In the experiment, this can be done using electrostatic fields. Florian Libisch and Joachim Burgdörfer (TU Vienna) provided computer simulations to calculate how the energy of the electrons changes in both materials and which voltage leads to an optimum yield of electrical power.

Tightly packed layers

"One of the greatest challenges was to stack the two materials, creating an atomically flat structure", says Thomas Mueller. "If there are any molecules between the two layers, so that there is no direct contact, the solar cell will not work." Eventually, this feat was accomplished by heating both layers in vacuum and stacking it in ambient atmosphere. Water between the two layers was removed by heating the layer structure once again.

Part of the incoming light passes right through the material. The rest is absorbed and converted into electric energy. The material could be used for glass fronts, letting most of the light in, but still creating electricity. As it only consists of a few atomic layers, it is extremely light weight (300 square meters weigh only one gram), and very flexible. Now the team is working on stacking more than two layers - this will reduce transparency, but increase the electrical power.

2D materials

Ultra-thin 2D materials, which consist only of one or a few atomic layers are a hot topic. Research on such materials started with graphene, which is made of a single layer of carbon atoms. Mueller and his team  applied their knowledge gained in handling, analysing and improving ultra-thin layers of graphene to other ultra-thin materials to do this work. The team was the first to combine two different ultra-thin semiconductor layers and study their optoelectronic properties.



AngelTech Live III: Join us on 12 April 2021!

AngelTech Live III will be broadcast on 12 April 2021, 10am BST, rebroadcast on 14 April (10am CTT) and 16 April (10am PST) and will feature online versions of the market-leading physical events: CS International and PIC International PLUS a brand new Silicon Semiconductor International Track!

Thanks to the great diversity of the semiconductor industry, we are always chasing new markets and developing a range of exciting technologies.

2021 is no different. Over the last few months interest in deep-UV LEDs has rocketed, due to its capability to disinfect and sanitise areas and combat Covid-19. We shall consider a roadmap for this device, along with technologies for boosting its output.

We shall also look at microLEDs, a display with many wonderful attributes, identifying processes for handling the mass transfer of tiny emitters that hold the key to commercialisation of this technology.

We shall also discuss electrification of transportation, underpinned by wide bandgap power electronics and supported by blue lasers that are ideal for processing copper.

Additional areas we will cover include the development of GaN ICs, to improve the reach of power electronics; the great strides that have been made with gallium oxide; and a look at new materials, such as cubic GaN and AlScN.

Having attracted 1500 delegates over the last 2 online summits, the 3rd event promises to be even bigger and better – with 3 interactive sessions over 1 day and will once again prove to be a key event across the semiconductor and photonic integrated circuits calendar.

So make sure you sign up today and discover the latest cutting edge developments across the compound semiconductor and integrated photonics value chain.

REGISTER FOR FREE

VIEW SESSIONS

Info
×
Search the news archive

To close this popup you can press escape or click the close icon.
×
Logo
×
Register - Step 1

You may choose to subscribe to the Compound Semiconductor Magazine, the Compound Semiconductor Newsletter, or both. You may also request additional information if required, before submitting your application.


Please subscribe me to:

 

You chose the industry type of "Other"

Please enter the industry that you work in:
Please enter the industry that you work in:
 
X
Info
X
Info
{taasPodcastNotification}
Live Event