Inorganic perovskites of a particular crystal configuration could outperform silicon in solar cells, scientists say.
AsianScientist (Sep. 3, 2019) – An international team of scientists has discovered a material that converts sunlight into electricity with greater efficiency than silicon. Their work is published in Science. Silicon dominates solar energy products due to its high stability, high energy conversion efficiency and low cost. Few materials have been discovered thus far that can dethrone silicon from its widespread use in energy settings. In the present study, researchers led by Professor Qi Yabing at the Okinawa Institute of Science and Technology in Japan, with collaborators in China, France and the US, have designed an inorganic material that surpasses silicon in terms of performance. Specifically, they used CsPbI3, what is known as an inorganic perovskite. CsPbI3 is often studied in its alpha phase, a well-known configuration of the crystal structure that results in a black color. This phase is particularly good at absorbing sunlight. Unfortunately, it is also unstable, and the structure rapidly degrades into a yellowish form which is less able to absorb sunlight. The researchers thus sought to study CsPbI3 in its beta phase instead, a less well-known arrangement of the structure that is more stable than its alpha phase. However, the beta phase is less efficient than the alpha phase in converting sunlight to electrical energy. This low efficiency partly results from the cracks that often emerge in thin-film solar cells. These cracks induce the loss of electrons into adjacent layers in the solar cell—electrons that can no longer flow as electricity, reporting that this solution also optimized the interface between layers in the solar cell. By repairing the cracks, this treatment led to an increase in conversion efficiency, from 15 percent to 18 percent. While that leap may seem small, it brings CsPbI3 into the realm of certified efficiency, the competitive value offered by rival solar materials, said the authors.