Researchers from CNR-IMM,CNR-IPCB, CNR-NANOTEC, Università Degli Studi di Messina and the University of Basel have shown that lead leakage can be prevented by applying a transparent titanium dioxide (TiO2) sponge in a semitransparent solar cell. The device has demonstrated comparable efficiency to semi-transparent perovskite devices and has an average visible transmittance (AVT) of 31.4%.
The team designed the solar cell for applications such as building-integrated photovoltaics (BIPV) and agrivoltaics, in which the potential lead leakage can be seen as a serious public environmental and health risk source.
TiO2, a highly adsorbent material, serves as an effective electron transport layer (ETL) in perovskite solar cells. To address potential lead (Pb) leakage, the researchers created a solvent-free porous TiO2 film, forming a sponge-like structure capable of capturing Pb from damaged cells during simulated catastrophic events. The researchers explained that the TiO2 sponge can sequester Pb in concentrations ranging from 24 g cm2 to 63 g cm2, which are equivalently contained in MAPbI3 layers with thicknesses from 200 nm (semi-transparent PSC) to 500 nm (opaque PSC).
They built the cell with a substrate made of glass and indium tin oxide (ITO), a hole transport layer (HTL) made of poly-triarylamine (PTAA), a perovskite absorber with the TIO2 sponge, an electron acceptor made of phenyl-C61-butyric acid methyl ester (PCBM), a bathocuproine (BCP) buffer layer, a gold (Au) metal contact, and the TIO2 sponge.
The scientists deposited the sponge via a physical solvent-free deposition, by using sputtering equipment, an easily up-scalable deposition method, which is widely used by semiconductors manufacturing companies. They added that a pre-sputtering step of 1 min is performed before the deposition process to clean up the surface of the titanium target to remove oxidized layers.
The solar cell reportedly achieved a power conversion efficiency of 11.6% and has an average visible transmittance (AVT) of 31.4%. The newly-devised method represents a step forward in addressing Pb release for BIPV, BAPV, agrivoltaics and opaque devices, and may also pave the way for Pb recycling in end-of-life devices.