Ultrathin inverted perovskite solar cells achieve 20.2% efficiency

Chinese scientists have developed ultralight solar cells based on perovskite thin films based on a 3-micrometer-thick polymer. The cell's power conversion efficiency is said to be comparable to conventional thickness perovskite cells.

Researchers at Peking University in China have developed an ultrathin perovskite solar cell based on Parylene C. Parylene C is a chlorinated poly(paraxylylene) polymer with high temperature resistance, low moisture permeability and excellent electrical and physical properties.

They used a commercially available 3-micron-thick parylene C and embedded it in the solar cell by flip transfer (FOT) technique. They claim that this ensures the smoothness of the polymer surface. They also deposited parylene C on pre-cleaned glass substrates using chemical vapor deposition (CVD).

In addition, the scientists used 210-nanometer-thick zirconium (Zr), titanium (Ti), and gallium-doped indium oxide (ITGZO) as the transparent conductive oxide (TCO) electrode for this solar cell. Using scanning electron microscopy (SEM), they compared the cell's performance with a benchmark device based on parylene F, another polymer, and a glass-substrate cell without the polymer.

The scientists said: "The perovskite film overlaid on Parylene F has poor coverage, multiple pinholes on the film surface, and interfacial voids at the embedded bottom interface, which will lead to charge accumulation and detrimental device performance. while the perovskite films fabricated on Parylene C achieved the same film formation uniformity as the glass-based films, as evidenced by the disappearance of surface pinholes and interfacial voids."

The Parylene C-based photovoltaic cell achieved a power conversion efficiency of 20.2 percent, which the researchers say is comparable to normal-thickness perovskite cells.

They concluded: "Due to the high power conversion efficiency (PCE) and the light weight of the device using the Parylene C substrate of 6.67 g/m², the power per unit weight reached 30.3 W/g, which shows that the use of Parylene C Lin C thin films have great prospects for making high-efficiency, ultra-thin, and ultra-light solar cells."

The researchers present their findings in the article "Ultralight and Flexible Perovskite Solar Cells" recently published in Science China: Materials.