The addition of quantum wells to solar cells vastly improves efficiency

High-efficiency solar cells are attractive for use in both space and terrestrial applications. Though Kesterite has been a promising material for use in photovoltaics, the theoretical upper limit on the efficiency of traditional Kesterite solar cells was predicted to be 29.7%, and experimental observations have been even lower. Despite efforts to improve this value, results have been unencouraging. To address Kesterite shortcomings, a new theoretical analysis by Maykel Courel investigates the effects of the addition of quantum wells on solar cell efficiency.

“Different and novel strategies are required to achieve this goal,” Courel said. “The addition of quantum wells to Kesterite solar cells is presented as an alternative potential route to solve this issue.”

By incorporating these quantum nanostructures into Kesterite cells, Courel showed the optimized photon absorption efficiency can be increased to 43.3%.

When quantum wells with small bandgaps are embedded into the bulk material, light absorption energies are reduced, allowing the absorption of additional photons with lower energies. Courel found by altering the width and depth of the quantum wells, the photon absorption can be maximized. The photogenerated electron-hole pairs then escape from the bulk cell, generating more current than they would without the inclusion of the nanostructures.

Though Courel does not anticipate this work being applied to commercial solar cells for another few decades, he is optimistic that the study will help researchers understand the effect of nanostructures in similar materials. “This opens the door to study the impact of other nanostructures, such as quantum dots and quantum wires, in thin film solar cells,” he said.

Source: “An approach towards the promotion of Kesterite solar cell efficiency: The use of nanostructures,” by Maykel Courel, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5110289 .