Nanyang team designs mini perovskite modules with 18.4% efficiency

Researchers from Singapore's Nanyang Technological University have developed a mini solar module based on thermally evaporated perovskites with an efficiency of 18.4% and a geometric fill factor (GFF) of around 91%. The team believes that the panel could be a real step forward in the industrialization of perovskite mini-modules.

The panel has an active area of 6.4 cm² and is based on co-evaporated methylammonium lead iodide (MAPbI₃). The thickness of the MAPbI₃ films was 750 nm, and the films were used to create solar cells with an 'n-i-p' layout on fluorine-doped tin oxide (FTO) glass substrates.

The researchers noted that a strong drop in the module efficiency ' from around 19% to 15% ' occurs when the cells are scaled up to 7.5 cm². This is caused by FTO sheet resistance, which determines the drop in the fill factor. To address this issue, the scientists chose a modular design based on the optimization of the size of the sub-cells and the dead areas.

They scaled up the size of the cells by maintaining a rectangular shape and a constant width.

'Both the careful design of the active areas and the high uniformity of co-evaporated perovskite film can guarantee minimal power efficiency losses during scaling up,' the researchers said.

The high fill factor is ensured by the fact that the number of sub-cells in the module can be increased, due to the modular design. However, this makes the geometric fill factor decrease, due to the higher number of connections.

'At the same time, minimizing the dead areas by reducing the number of connections and by reducing the width between the sub-cells can substantially increase the GFF,' researcher Subodh Mhaisalkar said. 'Our laser-etching scribing process could guarantee a dead area width of 0.06 cm which can achieve a GFF of 91%.'