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Iranian researchers have improved the efficiency of a perovskite solar cell by using a single-walled carbon nanotube as a hole transport layer surrounded by colloidal lead sulfide quantum dots.
Researchers at Tarbiat Modares University (TMU) in Iran have developed a perovskite solar cell using a hole transport layer (HTL) of single-walled carbon nanotubes (SWCNT). This SWCNT, a hollow cylinder of twisted graphene sheet, enhances hole transport within the cell. The researchers surrounded the nanotube with lead sulfide colloidal quantum dots (PbS-CQDs).
“The mentioned materials can absorb sunlight well and, in turn, increase the absorption and generation of carriers in the structure, thereby increasing the energy conversion efficiency,” the researchers say. “Furthermore, as the lifetime of the carriers in the PbS-CQDs material is close to 2000 ns, this causes less recombination of electrons and holes in the structure, which in turn leads to the increase of the open circuit voltage in the system".
The researchers built the cell using a carbon contact, with the SWCNT serving as the hole transport layer (HTL). The cell structure includes a MAPbI3 perovskite absorber, a titanium dioxide (TiO2) electron transfer layer (ETL), and an indium tin oxide (ITO) top contact.
“After finding the optimal SWCNT length and HTL height, we started scanning the center-to-center distance (CCD) between adjacent unit cell nanotubes from 5 nm to 30 nm,” the researchers explain. “The band gap of the selected SWCNT with the mentioned characteristics is equal to 1.3 eV.”
The research team determined that the optimal cell configuration and performance was obtained with the PbS-CQDs completely surrounding the SWCNT, with the HTL height set at 800 nm.
The final cell design, supported by simulations, achieved a power conversion efficiency of 19.98%, an open circuit voltage of 0.94 V, a short circuit current density of 24.45 mA/cm² and a factor 86% filling, which resolved the stability problems of the perovskite for its possible industrial use.
The study, “ Single-walled carbon nanotube as hole transport layer in perovskite solar cell: Efficiency enhancement, ” was recently published in Energy Reports. |
