Tarbiat Modares University (TMU) researchers in Iran have developed a perovskite solar cell using a single-walled carbon nanotube (SWCNT) hole transport layer (HTL). This SWCNT, a twisted graphene sheet hollow cylinder, 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 absorption and carriers' generation in the structure, thereby increasing the power conversion efficiency,” said the researchers. “In addition, since the carriers’ lifetime in 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 open-circuit voltage in the system.”
The researchers constructed the cell using a carbon contact, with the SWCNT serving as the hole transport layer (HTL). The cell's structure includes an absorber using MAPbI3 perovskite material, a titanium dioxide (TiO2) electron transfer layer (ETL), and a top contact composed of indium tin oxide (ITO).
“After finding the optimal length of SWCNT and HTL height, we start to sweep the center-to-center distance (CCD) between nanotubes of adjacent unit cells from 5 nm to 30 nm,” the researchers said. “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 resulted from PbS-CQDs fully surrounding the SWCNT, with the HTL height set at 800 nm.
This final cell design, supported by simulations, achieved a 19.98% power conversion efficiency, an open-circuit voltage of 0.94 V, a short-circuit current density of 24.45 mA/cm², and an 86% fill factor, addressing perovskite stability concerns for potential industry use.
The study, “Single-walled carbon nanotube as hole transport layer in perovskite solar cell: Efficiency enhancement,” was recently published in Energy Reports.
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