The team from the Energy Materials and Surface Sciences Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) worked with Prof. Shengzhong Liu from Shaanxi Normal University, China, to develop solar cells with materials that mimic the crystalline structure of the naturally occurring mineral perovskite and a new, lower cost manufacturing process.
Perovskite offers a more affordable solution than silicon but still faces lifetime and cost challenges, says Qi. "Research on perovskite cells is very promising. In only nine years, the efficiency of these cells went from 3.8 % to 23.3%. Other technologies have taken over 30 years of research to reach the same level," he said. The fabrication method he and his research team have developed produces perovskite solar cells with an efficiency comparable to crystalline silicon cells, but it is potentially much cheaper than making silicon solar cells.
To make the new cells, the researchers coated transparent conductive substrates with perovskite films. They used a gas-solid reaction-based technique in which the substrate is first coated with a layer of hydrogen lead triiodide incorporated with a small amount of chlorine ions and methylamine gas, allowing them to reproducibly make large uniform panels, each consisting of multiple solar cells.
In developing the method, the scientists found that making the perovskite layer 1 micron thick increased the working life of the solar cell significantly. "The solar cells are almost unchanged after working for 800 hours," says Dr. Zonghao Liu, a postdoctoral scholar in Prof. Qi's research unit at OIST. This thicker coating not only boosted the stability of the solar cells but also helped the fabrication processes, lowering its production costs. "The thicker absorber layer ensures good reproducibility of solar cell fabrication, which is a key advantage for mass manufacturing in the realistic industrial-scale setting," said Lui.
Next: Larger cells