Lightweight and flexible perovskites are the most promising materials for photovoltaics. However, their reported high performance has been about 20%, much lower than that of solid perovskites (25.7%).
Researchers at Nanjing University, Jilin University, Shanghai Tech University, and East China Normal University recently launched a new strategy to develop highly efficient solar cells based on flexible perovskites. This strategy, presented in a paper published in Nature Energy, involves using two selective hole molecules based on carbazole cores and phosphonic acid adhesion groups to seal perovskite with low-temperature NiO nanocrystal film.
“We believe that flexible light perovskite solar cells promise to create integrated photovoltaics, wearable electronics, portable energy systems and aerospace applications,” Hairen Tan, one of the researchers who conducted the study, told TechXplore. “However, its guaranteed high efficiency of 19.9% is lagging behind its strong counterparts (25.7% higher), largely due to faulty working areas in special connections with perovskites at the top.”
Previous studies have shown that making tandem solar cells using perovskites with different bandgaps can significantly increase the efficiency of single-cell solar cells based on flexible perovskites. In their latest research, Tan and colleagues found inspiration from previous findings to improve the efficiency of their solar cells dramatically.
“Our work builds on our previous work on solid solar cells in the perovskite tandem,” Tan explained. “Its main purpose was to find soft film solar cells with a higher PCE like that of their strong counterparts.”
Flexible solar cells and all perovskite tandem cells designed by researchers have a carefully studied design and structure. When their front cell, encased in a perovskite film with a wide band, is illuminated by the sun, it absorbs high-energy photons. On the other hand, its rear cell absorbs fewer energy photons than the front cell.
“Compared to solid perovskite solar cells, the lightweight perovskite tandem solar cells are more expensive to transport, store, and install, which makes them attractive in the construction / integrated vehicle of photovoltaics (PVs), portable electronics, portable power systems and more. and aerospace applications, “Tan said. “Compared to the flexibility of single-junction perovskite solar cells, flexible all-perovskite tandem solar cells can achieve higher efficiency.”
Tan and his colleagues used a combination of two selective hole molecules based on carbazole cores and phosphonic acid adhesion groups to form monolayer composites (SAM). Their experiments showed that SAM molecules could not be applied directly to ITO’s flexible PET substrates in flexible solar cells, as they led to mass capture of solar cells.
To overcome this challenge, Tan and his colleagues used NiO nanocrystals to create a layer of transport holes. Then they introduced a new hybrid SAM interface that they had designed between this port and the perovskite layer.