Small-molecule photovoltaics based on functionalized squaraine donor blends.

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Squaraine (SQ) dyes are promising organic semiconductors for solar energy conversion.
• Optimizing light absorption across the solar spectrum is crucial for enhancing photovoltaic efficiency.
• Previous studies focused on single-donor systems, limiting spectral coverage.

Purpose of the Study:

• To improve the power-conversion efficiency (PCE) of organic solar cells by enhancing spectral coverage.
• To investigate the synergistic effects of blending two squaraine donor molecules with distinct absorption bands.
• To optimize device architecture and processing for maximum PCE.

Main Methods:

• Synthesis and characterization of two squaraine donor molecules with complementary absorption spectra.
• Fabrication of bulk heterojunction organic solar cells using blended SQ donors.
• Optimization of film morphology via solvent annealing.
• Integration of a compound buffer layer to improve charge extraction.

Main Results:

• The blended SQ donor system exhibited broader solar spectrum absorption compared to single SQ donors.
• Devices incorporating the blended SQ donors showed significant performance improvements.
• Solvent annealing and the compound buffer layer were critical for achieving high efficiency.
• A champion power-conversion efficiency of 5.9 ± 0.3% was recorded under 1 sun illumination.

Conclusions:

• Blending squaraine donor molecules is an effective strategy to enhance light harvesting in organic solar cells.
• Advanced processing techniques like solvent annealing and buffer layer engineering are vital for realizing high-performance organic photovoltaics.
• The achieved efficiency demonstrates the potential of tailored organic materials for efficient solar energy conversion.