In a recent study, researchers develop new solar cells that uses inexpensive, commonly available materials. The new solar cells can rival and even outperform conventional cells made of silicon.
The finding is published in Science. Researchers from Stanford and Oxford describe using tin and other abundant elements to create novel forms of perovskite – a photovoltaic crystalline material that’s thinner, more flexible and easier to manufacture than silicon crystals.
In the study, researchers designed a robust, all-perovskite tandem device that converts sunlight into electricity with an efficiency of 20.3%, a rate comparable to silicon solar cells on the market today.
Perovskite solar cell can be processed in a laboratory from common materials like lead, tin and bromine, then printed on glass at room temperature.
However, building an all-perovskite tandem device is not easy. The main problem is creating stable perovskite materials capable of capturing enough energy from the sun to produce a decent voltage.
A typical perovskite solar cell harvests photons from the visible part of the solar spectrum. Higher-energy photons can cause electrons in the perovskite crystal to jump across an “energy gap” and create an electric current.
A solar cell with a small energy gap can absorb most photons but produces a very low voltage. A cell with a larger energy gap generates a higher voltage, but lower-energy photons pass right through it.
The smaller gap has proven to be the bigger challenge for scientists. In the study, researchers used a unique combination of tin, lead, cesium, iodine and organic materials to create an efficient cell with a small energy gap.
One concern with perovskites is stability. Rooftop solar panels made of silicon typically last 25 years or more. But some perovskites degrade quickly when exposed to moisture or light. In previous experiments, perovskites made with tin were found to be particularly unstable.
To assess stability, the research team subjected both experimental cells to temperatures of 212 degrees Fahrenheit (100 degrees Celsius) for four days.
The result showed that the new solar cells exhibited excellent thermal and atmospheric stability, unprecedented for tin-based perovskites.
The efficiency of the tandem device is already far in excess of the best tandem solar cells made with other low-cost semiconductors, such as organic small molecules and microcrystalline silicon.
In their next step, the researchers will optimize the composition of the materials to absorb more light and generate an even higher current.
News source: Stanford University.
Figure legend: This Knowridge.com image is credited to Rongrong Cheacharoen/Stanford University.