High-performance bifacial perovskite solar cells driven by single-walled carbon nanotubes

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  1. Proposed a method using single-walled carbon nanotubes as the counter electrode of a bifacial light-absorbing perovskite cell and achieved a bifacial efficiency of more than 36% and a bifaciality factor of more than 98%.

  
  

  2. The research results are suitable for flexible substrates. The flexible all-carbon electrode battery shows a bifacial efficiency of nearly 32% and a bifaciality factor of nearly 97%.

  
  

  3. This article simulates the short-term and long-term power generation of this type of battery and compares it with the power generation of silicon cells.

  
  

  1. Research background

  
  

  In the pursuit of better utilization of light energy, bifacial photovoltaics emerged and became a benchmark for innovation. Perovskite cells have shown great potential under low-light conditions, showing superior voltage and smaller losses, making them a strong contender for new bifacial photovoltaics.
  

  
  

  In order to absorb as much ambient reflected light energy as possible, the counter electrode must be highly transparent, stable, and compatible with each layer of the perovskite cell. Traditional electrode materials indium tin oxide (ITO) and fluorine-doped oxide (FTO) suffer from their inherent fragile characteristics, which greatly limits their wide application in flexible devices. In addition, the high-temperature deposition process may also have adverse effects on the perovskite layer.

  
  

  Based on this, the Wei Zhang team at the University of Surrey proposed a feasible method in "Nature Communications": using single-walled carbon nanotubes (SWCNT) as a Counter electrode of perovskite cells. This method not only improves the transparency and conductivity of the electrode, but its hydrophobicity increases the battery life to a great extent. In addition, the simple preparation method also provides new ideas for flexible devices.

  
  

  2. Results and discussion

  
  

  Point 1: Characterization of photoelectric properties of SWCNTs

  Optical and electrical characterization (Figure 1) shows the excellent properties of SWCNT, making its physical properties meet the requirements of transparent electrodes for perovskite cells. Its higher optical transmittance and strong electrical conductivity, coupled with a better G/D ratio (IG/ID=162) peak, show that it has fewer defects, paving the way for effective electron transmission. Ultraviolet photoelectron spectroscopy revealed that the work function of SWCNT is -4.70 eV, which is almost the same as ITO, further showing its great potential as a transparent electrode.

  
  

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• Point 2: Characterization of all-carbon electrode perovskite bifacial cells

  Subsequently, devices were prepared using SWCNTs as counter electrodes and their related properties were tested (Figure 2). The results show that the efficiency of these bifacial cells has been improved accordingly in different reflection scenarios. By removing ITO and metal electrodes, the lifespan of these all-carbon electrode perovskite bifacial batteries is greatly improved. These data show the great potential of SWCNT electrodes in preparing efficient and stable bifacial perovskite cells.

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• Point 3: Power generation simulation

  The power generation of this type of bifacial perovskite cell in 2025 was then simulated based on our climate model (Figure 3). In June, when there is plenty of sunshine, its peak power generation can reach 35 kilowatt hours. Looking ahead 26 years (from 2025 to 2050), these bifacial cells could provide more than 300 kilowatt hours of electricity per year. Using SWCNT as an electrode significantly improves the photoelectric conversion rate. Especially in urban areas where glass is widely used, the reflected light on the glass surface can provide higher reflected energy for bifacial cells, further improving cell efficiency.

  
  
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• Zhang, J., Hu, XG., Ji, K. et al. High-performance bifacial perovskite solar cells enabled by single-walled carbon nanotubes. Nat Commun 15, 2245 (2024).

  
  

  https://doi.org/10.1038/s41467-024-46620-1.