Researchers from the University of Toronto‘s Faculty of Applied Science and Engineering studied the inverted perovskite solar cell structure at the Sargent Group lab in the quest to find an alternative solar technology that is energy-efficient and affordable.

Currently, most solar cells are manufactured using high purity silicon, which consumes significant energy. Researchers from the University of Toronto claim to have discovered an alternative that can be a potential substitute for silicon without compromising the stability of solar cells.

The researchers used quantum mechanics to channel the active layer in an inverted perovskite solar cell. Postdoctoral researcher in Sargent lab, Hao Chen, along with co-lead authors Sam Teale and postdoctoral researcher Bin Chen and Yi Hou, reversed the perovskite solar cell structure to enable alternate manufacturing techniques.

According to Chen, roll-to-roll printing in manufacturing perovskite crystal makes it eligible for mass production at a much lower cost than silicon. However, the orderly arrangement of atoms in perovskite solar cells destabilizes when exposed to sunlight.

Electrons move out through a negative electrode at the bottom layer of the cell in prototype perovskite solar cells, with holes they leave behind as they exit through a positive electrode at the top. Researchers have previously reversed this process to enhance the stability of the perovskite layer. However, the alteration in cell structure affects the performance.

“Researchers typically insert a passivation layer made of organic molecules. That works really well in the traditional orientation because ‘holes’ can go right through this passivation layer. But electrons are blocked by this layer, so when you invert the cell, it becomes a big problem,” Chen further added

The team eliminated the organic layer by producing a two-dimensional perovskite surface over their solar cell, enabling the solar cell to achieve passivation.

Researchers then increased the width of the perovskite layer and increased its height from one to three crystals to address the electron blocking effect. The change in dimensions of the layer resulted in an altered energy landscape that is enough to enable electrons to exit into an external circuit.

The team found that after the above treatment, the power conversion efficiency of their perovskite cell was 23.9%. Even after 1,000 hours of operation at room temperatures, the efficiency level did not fade. The consistency in performance decreased only by 8% when the cell was exposed to an industry-standard accelerated aging process at temperatures up to 65 degrees Celsius after more than 500 hours of use.

The team at the University of Toronto aims to develop cells with a larger surface area so that perovskites can be studied for agility in higher temperatures. The cells used in this research were only about five square millimeters in size.

One of the paper’s co-authors, Sam Teale, said, “The combination of high stability and high efficiency we achieved really stands out. We should also remember that perovskite technology is only a couple of decades old, whereas silicon has been worked on for 70 years. There are a lot of improvements still to come.”

Mercom recently reported a similar approach by scientists at UCLA School of Engineering, where they demonstrated a new surface treatment process during the manufacture of perovskite solar cells. They claimed that the new adjustment helps avoid the deterioration of cells when exposed to the sun.