16.63%-efficient perovskite PV module via slot-die coating


Researchers at the Huazhong University of Science and Technology, in China, have developed a perovskite solar module with an active area of 20.77cm2.

The scientists used diphenyl sulfoxide (DPSO) as an electron acceptor and combined it with a formamidinium-cesium (FACs) perovskite precursor solution. “DPSO is demonstrated to impressively enlarge the nucleation energy barrier, effectively retard the natural nucleation of perovskite during the slot-die coating process, and stabilize the wet precursor film,” they explained.

Slot-die coating, which is a coating process used for depositing thin and uniform films with limited material waste and low operational cost, was used to place the FACs perovskite films on a fluorine-doped tin oxide (FTO)/NiMgLiO substrate with a size of 20x14cm. “Film thickness could be simply controlled by adjusting the concentration of the perovskite precursor ink,” the Chinese group stated, adding that the film showed homogeneous photoluminescence intensity and good uniformity.

The film was cut into 12 pieces, each with a size of 4x4cm, with which 18%-efficient solar cells with an active area of 1cm2 were built. The cells were then assembled in a parallel-interconnection architecture to form the large-area module. This design is said to avoid direct contact between the perovskite and the metal electrode, which would be, otherwise, detrimental to module stability.

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Furthermore, the researchers explained that an ultrathin lithium fluoride (LiF) interlayer was used to improve the films’ surface passivation and, as a result, the panel's open-circuit voltage, and that a bismuth interlayer was utilized to prevent silver interdiffusion and the metal's reaction with perovskite, which could affect the module's stability.

The performance of the p-i-n-structured panel was analyzed by the Newport PV Lab in Montana, in the U.S., which ascertained that the device achieved a power conversion efficiency of 16.63%. “The encapsulated modules maintained 97% and 95% of their initial efficiencies after 10,000 and 1,187 hours under day/night cycling … respectively,” said the Newport researchers, who added, the devices were tested under “one-sun-equivalent, white-light, light-emitting diode array illumination, with maximum power point tracking at 50 degrees Celsius.”

The research team believes that the proposed manufacturing technique may be used for the commercial production of large-area perovskite PV panels. The device was described in the paper Slot-die coating large-area formamidinium-cesium perovskite film for efficient and stable parallel solar module, published in ScienceAdvances.

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