Organic Semiconductor Makes Perovskite Solar Cells More Efficient

Organic Semiconductor Makes Perovskite Solar Cells More Efficient

Author: Sarah Maier

Demand for energy from renewable sources, e.g., solar energy, is steadily growing due to climate change and other environmental and political issues associated with the use of fossil fuels. Lead-halide perovskites are suitable materials for use in solar cells. Their onset of light absorption typically lies around 800 nm, however. Thus, the near-infrared (NIR) part of the solar spectrum cannot be used for the generation of energy.

Yueh-Lin Loo, Princeton University, NJ, USA, and colleagues have extended the absorption spectrum of a lead-halide perovskite solar cell into the NIR region by adding the narrow-bandgap organic semiconductor IEICO-4F (pictured). This semiconductor is able to undergo efficient charge transfer with the perovskite and also serves as a Lewis base. Due to this Lewis basicity, IEICO-4F stabilizes the perovskite layers by passivating defects within the layers.

The researchers synthesized perovskite solar cells with IEICO-4F, without an additive, and with poly(methyl methacrylate) (PMMA) and compared their photocurrent generation. PMMA was used as a reference because it passivates the perovskite defects without broadening the absorption range. During synthesis, perovskite layers are treated with a solvent to control crystallization. IEICO-4F or PMMA was added to this solvent and, thus, deposited at the perovskite grain boundaries.

Incorporation of IEICO-4F led to 21.5 % efficiency for  the modified perovskite cell compared to 20.0 % for the pristine cell. The modified cell also displayed improved stability. The efficiency of the PMMA-modified cell was lower at 20.4 %, which shows the effect of the additional absorption. These positive first results indicate that additives which simultaneously act as narrow-bandgap semiconductors with NIR absorbance and as Lewis bases are promising for improving the performance of perovskite solar cells.


 

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