Hybrid perovskites have emerged as key components in low-cost, high-efficiency solar cells because they are cheaper and easier to process than traditional silicon-based solar cell materials. In addition, they exhibit unique optoelectronic characteristics, including high light absorption and a defect tolerance that lead to solar cells with maximum power-conversion efficiencies of 24 to 28 percent when used alone or in tandem combination with silicon. They also outperform single-junction silicon solar cells.
“Our study provides critical insights into the crystallization of the multicomponent systems toward high-performance perovskite solar cells,” Wang says. Changes in the compositions of the halide and cation dramatically affected the solidification of the perovskite precursors during spin coating and the subsequent formation of the desired α-phase upon antisolvent addition.
The period needed to generate high-quality films by antisolvent addition ended when the sol-gel structure collapsed to produce crystalline by-products depending on the precursor mixture. Consequently, tuning the halide-cation mixture could delay this collapse, widening the antisolvent dripping window from a few seconds to several minutes. As well, simultaneously incorporating cesium and rubidium cations in the perovskite synergistically stimulated the formation of the α-phase. The length of this window showed little effect on resulting solar cell performance as long as the antisolvent was added within this period.
These findings suggest new directions for the development of perovskite formulations that can further stabilize the sol-gel state and promote its conversion to the desirable perovskite phase. “This is critical in achieving better-performing, reproducible, cost-efficient and scalable manufacturing of perovskite solar cells,” Wang says.
The team is working on transferring this knowledge to other deposition technologies to progress toward market-ready perovskite solar cells.
Source and top image: KAUST