German researchers have produced a carbon electrode perovskite solar cell with a hole-transporting double layer made of organic semiconductors instead of a conventional hole-transporting layer. They claim that this approach improves the device’s duty cycle and open circuit voltage.
They explained that replacing expensive gold, silver and copper with carbon in perovskite solar cells typically causes efficiency losses and stability issues compared to reference devices. “For printable cells, we ultimately aim to transfer this technology to a roll-to-roll production line,” said co-author Tian Du. pv magazinepoints out that the next steps on the road to commercialization are to manufacture a mini-solar module on glass substrates, then a mini-solar module on a flexible substrate, and then transfer to roll-to-roll manufacturing.
The German team built the cell from a glass and indium tin oxide (ITO) substrate, an electron transport layer (ETL) based on tin(IV) oxide (SnO2), a perovskite absorber, a hole transporting double layer (HTbl). and carbon contact. “The HTbL configuration creates an energy cascade at the interface, where the outer HTL 2 strengthens the ohmic contact with the carbon, while the inner HTL 1 reduces the surface.
perovskite recombination,” it explained.
As an absorber, they used a mixed-cation perovskite known as (FAPbI3)0.93 (MAPbBr3)0.07. They deposited two layers with a back-to-back blade coating, which they said could maximize hole injection/extraction at the electrode interface while minimizing surface recombination of the perovskite layers.
They tested the device under normal lighting conditions and found that it achieved a power conversion efficiency of 19.2%, an open-circuit voltage of 1.11V, a short-circuit current of 23.7A, and a duty cycle of 76%. For comparison, a reference cell with a single-hole transfer layer achieved an efficiency of 17.3%, an open-circuit voltage of 1.06 V, a short-circuit current of 23.3 A, and a duty cycle of 76%.
The bilayer-based cell also showed stable operation for 2500 hours at 65 C in a nitrogen environment.
The cell is described in a 2010 study titled “Efficient, Stable, and Fully Printed Carbon Electrode Perovskite Solar Cells Enabled by Hole-Transporting Bilayers.” Joule. The research group consists of researchers from the Institute of Materials for Electronics and Energy Technology (i-MEET) and the Institute of Micro- and Nanostructure Research & Center for Nanoanalysis and Electron Microscopy (CENEM).
“Our results highlight that carbon electrodes can significantly improve the intrinsic stability of a perovskite solar cell without special interface modifications,” they concluded.