Tin Monosulfide Crystal Opens Pathway for Next Gen Solar Cells

A team of scientists has developed a new process for the fabrication of crystal Tin Monosulfide, which opens the door for it to be introduced in PV cells

Tin Monosulfide (SnS) has long been considered a potential alternative to the sometimes rare, expensive and toxic materials used in today’s solar photovoltaic cells. And now, a team of scientists at Japan’s Tohoku University has developed a new process for the fabrication of crystalline SnS, which opens the door for SnS – the cheap and abundant material – to be formally introduced in PV cell design.

While SnS is known as a cheap, abundant material with promising characteristics for use in solar cells, it has proved a challenging material to work with, as researchers have struggled to achieve conversion efficiencies better than 5 percent with this material, and interest from the research community has lagged behind that of kesterite, or copper-zinc-tin, solar cells.

According to the team led by Sakiko Kawanishi and Issei Suzuki at Took University, the objective is to create a p-n homojunction, which consists of p-type and n-type SnS. This is key to obtaining SnS solar cells with high efficiency. However, it was the manufacturing of such solar cells until now that proved difficult due to the complexity of fabricating n-type SnS in contrast to the easily fabricable p-type SnS.

But the team has succeeded in growing large single crystals of SnS, which can provide a pathway for the fabrication of SnS solar cells with a high conversion efficiency.

To solve the problem, the team designed an original feed composition used for the flux growth of SnS crystals. This is something that had not been successfully trialled before. A dramatic change appeared in the grown crystals by halogen addition, that is, enlargement of the crystal size to a maximum 24 mm in width, in addition to including an n-type conduction characteristic. The larger crystals lower the stakes of trial manufacturing the SnS solar cells with p-n homojunction, which accelerates the development for practical application.

The growth process is described in the paper Growth of Large Single Crystals of n-Type SnS from Halogen-Added SnS Flux, published in the journal Crystal Growth and Design. The group went on to measure the electrical characteristics of the thin film, observing encouraging electrical conductivity characteristics and confirming the material’s n-type conductivity.

Another material that has been in the talk for replacing today’s solar cells and modules is Perovskites. Different from the traditional silicon wafers that make up solar cells and panels of today – Perovskites have a unique crystallographic structure that makes them more effective at converting photons of light from the sun into usable electricity. Perovskites have generated excitement because solar cells that have a coating of Perovskite are delivering energy efficiencies of 25 percent and over in lab conditions, with just under 10 years of research in the sector.

Read more Perovskite Solar Cells, Coming Soon To a Product Near You