Boosting Organic Solar Cell Performance via Light-Assisted Crystallization of P3HT:PCBM Blend

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Poly-(3-hexylthiophene) (P3HT) and P36,6]-phenyl-C61-butyric acid methyl ester (PCBM) are key materials in organic solar cells.
• Optimizing film morphology and crystallinity is crucial for efficient charge generation and transport.
• Conventional annealing methods may not fully exploit the potential of these materials.

Purpose of the Study:

• To investigate the impact of halogen-light-assisted (LA) annealing on P3HT film crystallization.
• To evaluate the effect of LA annealing on the morphology of P3HT:PCBM blend films.
• To determine the influence of LA annealing on organic solar cell performance.

Main Methods:

• Annealing of P3HT films and P3HT:PCBM blends using conventional hot plate (HP) and LA methods at temperatures from 100-120 °C for 5-15 min.
• Structural analysis using X-ray diffraction (XRD) and atomic force microscopy (AFM).
• Device fabrication and characterization, including current-voltage (J-V) measurements.
• Charge transport and recombination studies using time-resolved photoluminescence (TRPL) and space charge limited current (SCLC) measurements.

Main Results:

• LA annealing significantly enhanced P3HT film crystallinity via improved in-plane molecular stacking.
• Optimal LA annealing at 100 °C for 15 min yielded a power conversion efficiency (PCE) of 3.10% for P3HT:PCBM solar cells, compared to 2.22% for HP-annealed devices.
• P3HT-rich compositions (1:0.6 ratio) showed the greatest improvement in film morphology and efficiency with LA annealing.
• LA annealing improved charge carrier mobility, reduced trap densities, and minimized nonradiative recombination.

Conclusions:

• Halogen-light-assisted (LA) annealing is an effective method for enhancing P3HT film crystallinity and P3HT:PCBM blend morphology.
• LA annealing leads to significant improvements in organic solar cell performance, achieving higher PCEs.
• The study demonstrates LA annealing as a scalable technique for high-performance organic solar cells.