New doping strategy increases lead-free perovskite solar cell efficiency


A group of researchers led by the University of Lahore in Pakistan have developed a solar cell based on an absorber made with a lead-free perovskite material known as Cs2AgBiBr6.

The novelty of their approach consisted of doping the material with polyacetylene (PA), which is one of the most promising organic polymers for applications in optoelectronics. This doping process is intended at reducing the high energy bandgap of the Cs2AgBiBr6. material, which the scientists indicated at 1.9 eV.

“The decrease in energy gap is a result of adjusting the edges of the conduction and valence bands, while it leads to the increase of electrons injection from perovskite layer to electron transport layer,” they explained. “The increase in the peak intensity clarified the crystallinity of the material.”

At the end of the doping process, the perovskite material had an energy bandgap of 1.84 eV.

The team built the solar cell with a substrate made of glass and fluorine-doped tin oxide (FTO), an electron transport layer (ETL) relying on a titanium oxide (TiO2), the perovskite absorber, hole transport layer (HTL) based on Spiro-OMeTAD, and a gold (Au) metal contact.

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The researchers tested the performance of the solar cell under standard illumination conditions and found it achieved a power conversion efficiency of 3.98%, an open-circuit voltage of 0.929 V, a short-circuit current density of 5.7 mA/cm2, and a fill factor of 75%. A reference device with no doping achieved an efficiency of 3.29%, an open-circuit voltage of 0.920 V, a short-circuit current density of 5.13 mA/cm2, and a fill factor of 69%.

“These improvements together with the aforementioned amelioration of the band gap may open promising avenues for the future commercialization of high-performance solar-energy harvesting technologies,” the academics stated.

They introduced the new cell concept in “Trans-polyacetylene doped Cs2AgBiBr6: Band gap reduction for high-efficiency lead-free double perovskite solar cells,” which was recently published in Results in Physics. “The study shows the mechanical and dynamical stability of the Cs2AgBiBr6,” they concluded.

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