Correlation between blend morphology and recombination dynamics in additive-added P3HT:PCBM solar cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Bulk heterojunction (BHJ) organic solar cells rely on morphology for power conversion efficiency.
• High boiling point solvents can be used to control blend morphology in organic solar cells.

Purpose of the Study:

• Investigate the effects of thiol-based additives (PDT, HDT, ODT) on P3HT:PCBM blend films.
• Establish a relationship between morphology, charge dynamics, and photovoltaic performance.
• Optimize organic solar cells without thermal annealing.

Main Methods:

• Transient absorption spectroscopy (TAS) to study charge dynamics.
• Physical characterizations to analyze film morphology.
• Device fabrication and performance testing.

Main Results:

• HDT and ODT additives improved power conversion efficiency (2.8%) compared to PDT (1.7%) and control samples.
• Additive-treated films showed more efficient initial exciton and polaron generation.
• HDT and ODT mimic the performance of thermally annealed films, while PDT leads to trap-assisted recombination.

Conclusions:

• Thiol-based additives effectively control phase separation and P3HT ordering in BHJ films.
• Efficient charge carrier transport and collection are crucial for high performance.
• Understanding the interplay of crystalline order, phase separation, and percolation is key for optimizing additive-treated organic solar cells.