Researchers at the University of Toronto Engineering and King Abdullah University of Science and Technology (KAUST) have beat out a critical obstacle in combining the emerging solar-harvesting technology of perovskites with the commercial gold standard—silicon solar cells.
The result is a highly powerful and stable tandem photovoltaic cell, one of the best-performing reported to this point. Like silicon, perovskite crystals can absorb photovoltaic energy to excite electrons that can be channeled into a circuit.
However, unlike silicon, perovskites could be mixed with liquid to create a ‘solar ink’ that can be printed on surfaces.
Like silicon, perovskite crystals can absorb photovoltaic energy to excite electrons that can be channeled into a circuit. However, unlike silicon, perovskites could be combined with a liquid to create a ‘solar ink’ that can be printed on surfaces.
The ink-based manufacturing strategy—often called solution processing—is already well-established in the printing sector, and has the potential to lower the price of making photovoltaic cells.
Though they could look smooth, standard silicon wafers used for photovoltaic cells feature small pyramidal structures about two micrometers high.
The uneven surface minimizes the amount of light that reflects the surface of the silicon and increases total performance, but also makes it troublesome to coat a uniform layer of perovskites on top.
Hou and the rest of the group—along with Sargent and KAUST Prof Stefaan De Wolf—followed a different strategy. They increased the thickness of the perovskite layer, making it high enough to cover both the peaks and the valleys formed by the pyramidal buildings.
The team enhanced charge separation by coating the perovskite crystals in a ‘passivation layer’ made from 1-butanethiol, a regular industrial chemical compound.