A group of scientists in China has designed a perovskite solar cell based on a functionalized two-dimensional titanium carbide (Ti3C2Tx), which is also known as MXene.
MXenes compounds take their name from their graphene-like morphology and are made via selective etching of certain atomic layers from a bulk crystal known as MAX. Recently, MXenes materials have shown promise for use in PV technology due to their unique optoelectronic properties, such as their large charge carrier mobility, excellent metallic conductivity, high optical transmittance, and tunable work function (WF).
The research team used two surface-functionalization strategies for MXene with dodecyltrimethoxysilane and fluoroalkylsilane (FOTS) molecules, respectively, to form a self-assembled monolayer on the MXene itself.
“At first, we added unmodified MXene to the electron transport layer (ETL), which didn’t have a big impact,” said researcher Li Yin. “However, we realized that slightly adjusting the chemical structure of the MXene may also modify the other materials in the electron transport layer. This would reduce barriers to electron movement and improve the performance of the solar cells. We were right.”
According to the researchers, the functionalized MXene dopants resulted in a larger grain size and a higher open-circuit voltage for the PV device. The solar cell architecture consists of an indium tin oxide (ITO) substrate, an electron transport layer (ETL) based on Tin(IV) oxide (SnO2) and doped with MXene-H, the perovskite layer, a spiro-OMeTAD hole-blocking layer, and a silver (Ag) metal contact.
The champion solar cell built with this configuration achieved a power conversion efficiency of 23.66%, an open-circuit voltage of 1.095 V, a short-circuit current of 25.07 mA/cm2, and fill factor of 83.18%. A reference cell without MXene-H achieved a power conversion efficiency of 20.98%, an open-circuit voltage of 1.062 V, a short-circuit current of 25.01 mA/cm2, and fill factor of 80.60%.
“Both optimal devices show higher moisture-resistance stability and operation stability,” the scientists said. “For light stability, it is clear that after 1,000 h of illumination, the device based on SnO2-MH as the ETL maintains almost 80% of its initial efficiency.”
They presented the cell technology in “Functionalized-MXene-nanosheet-doped tin oxide enhances the electrical properties in perovskite solar cells,” which was recently published in Cell Reports Physical Science. The research group includes academics from the University of Science and Technology of China, the Xi’an Jiaotong-Liverpool University, and the University of Liverpool in the United Kingdom.
“This work provides a promising potential direction toward achieving high-quality SnO2 ETLs, and we believe that the desired modifications to the dopant could further enhance the device performance preferably,” they concluded.
Separately, another international research group recently conducted a review to find out how two-dimensional transition metal carbides and nitrides known as MXenes could be used as materials for solar cells. They presented their findings in “2D MXene: A Potential Candidate for Photovoltaic Cells? A Critical Review,” which was recently published in Advanced Science. The research group includes scientists from Dongguk University, Korea University, and Hamad Bin Khalifa University (HBKU).
“This systematic review is both expected to provide a way to realize the diverse nature of MXene composites from a different perspective, and open new directions to find solutions for next-generation PV applications,” the scientists said.
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