Well-aligned Vertically Oriented ZnO Nanorod Arrays and their Application in Inverted Small Molecule Solar Cells.

Area of Science:

• Materials Science
• Renewable Energy
• Nanotechnology

Background:

• Efficient fabrication of inverted solar cells is crucial for renewable energy advancements.
• Utilizing nanostructures like zinc oxide nanorods (ZnO NRs) can enhance solar cell performance.
• The quality of the seed layer, such as aluminum-doped zinc oxide (AZO), significantly impacts nanorod growth and device efficiency.

Purpose of the Study:

• To design and fabricate efficient inverted solar cells using ZnO NRs on an AZO seed layer.
• To investigate the effect of different AZO seed layer preparation methods (sputtered vs. sol-gel) on ZnO NR growth and solar cell performance.
• To optimize the structure for improved light harvesting and carrier collection.

Main Methods:

• Fabrication of inverted small molecule organic solar cells (SMPV1:PC71BM) using ZnO NRs.
• Growth of ZnO NRs on both sputtered and sol-gel processed AZO seed layers.
• Characterization using X-ray diffraction (XRD) and atomic force microscopy (AFM) to analyze AZO film quality and ZnO NR morphology.
• Performance evaluation of the fabricated solar cells, including power conversion efficiency (PCE) and fill factor (FF).

Main Results:

• Sputtered AZO seed layers exhibited superior crystallization and lower surface roughness compared to sol-gel processed AZO.
• ZnO NRs grown on sputtered AZO showed better vertical alignment, leading to improved active layer morphology.
• The optimized device achieved a power conversion efficiency (PCE) of 6.01%, significantly higher than the 4.74% achieved with sol-gel processed AZO.
• Well-aligned ZnO NRs enhanced carrier collection and acted as an anti-reflection structure, boosting light harvesting.

Conclusions:

• Sputtered AZO seed layers facilitate the growth of vertically aligned ZnO NRs, crucial for efficient inverted solar cells.
• The nanorod structure improves carrier collection and light absorption, leading to higher power conversion efficiency (PCE).
• This fabrication approach offers a promising route for developing high-performance organic solar cells.