ScienceJanuary 5, 2022

☀ Solar cell materials

Halide perovskite and buckyballs: Route to efficient and stable solar cell materials…
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Victor Milman

Halide perovskite and buckyballs: Route to efficient and stable solar cell materials

Solar energy plays an increasingly important role in the overall energy production.

Market data shows that by 2020 several countries led by Germany, Italy, Spain, Greece, UK, Australia were getting over 5%, sometimes close to 10% of their energy from solar power.

This progress is of course linked to materials research – it is imperative to have photovoltaic materials that are efficient in converting solar energy to electricity.

Conversion efficiency improved from 2-3% to 20-25%, and, in some cases, 40%, over the last years.

There is still a lot to be done to produce even more efficient converters.

BIOVIA’s Riichi Kuwahara is one of the authors of the recent paper “Photo-energy conversion efficiency of CH3NH3PbI3/C60 heterojunction perovskite solar cells from first-principles” in Materials Advances.

This work used BIOVIA Materials Studio DMol3 solver to look into conversion efficiency of the interface between a halide perovskite, MAPbI3, and a C60 buckyball.

The study showed that under certain alignment conditions an efficiency of 19% can be achieved. A more fundamental result of this study is a better understanding of the role of dipoles in the perovskite structure for electron transfer across the interface. This investigation gives a solid basis to future work on applications of ferroelectrics and electrical poling to improve efficiency of halide perovskite solar cells.

Figure 1. Schematic illustration of the energy-level diagram for the MAPbI3 and C60 in the hybrid perovskite/fullerene heterojunction. Eg is the energy gap of MAPbI3 and E is the dissociation energy of the electron-hole pairs. The three-fold degenerate LUMO of C60 fullerene has three energy level from LUMO to LUMO+2.

Further research showed that buckyballs not only improve conversion efficiency, but can be used reduce degradation and improve air stability. BIOVIA’s Riichi Kuwahara was part of the group of authors of “Electronic structure of Li+@C60 adsorbed on methyl-ammonium lead iodide perovskite CH3NH3PbI3 surfaces” paper in Materials Advances, the work that helps to understand one particular mechanism for MAPbI3 perovskite stabilization.

This study looks at doping of surfaces with Li+@C60 complexes to suppress surface oxidation of MAPbI3 perovskite.

The work was done with Materials Studio DMol3 and showed why the modified material is a good hole conductor – better than just Li-doped perovskite.

An energetically isolated hole level localized in the Li@C60 complex helps to suppress surface oxidation and makes material more stable on air. This conclusion is valid for any adsorption geometry on the MAPbI3 perovskite surface, making buckyballs a reliable stabilizer for this solar cell material.

Materials Studio

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