Dicyanoquinodimethane-substituted benzothiadiazole for efficient small-molecule solar cells

Area of Science:

• Organic electronics
• Materials science
• Photovoltaics

Background:

• Benzothiadiazole derivatives are promising organic semiconductors for solar cells.
• Donor-acceptor-acceptor-π-acceptor architectures offer tunable electronic properties.

Purpose of the Study:

• To synthesize and characterize novel benzothiadiazole-based materials (BTD3 and BTD4).
• To investigate the effect of two-step annealing (TSA) on the performance of organic solar cells incorporating these materials.

Main Methods:

• Synthesis of unsymmetrical donor-acceptor-acceptor-π-acceptor benzothiadiazoles (BTD3, BTD4) with TCBD and DCNQ modules.
• Fabrication of bulk heterojunction solar cells using BTD3:PC71BM and BTD4:PC71BM active layers.
• Application of chloroform (CF) processing followed by thermal annealing and solvent vapor annealing (TSA).

Main Results:

• BTD3 and BTD4 exhibit strong visible light absorption.
• TSA treatment significantly enhances power conversion efficiencies (PCEs) to 6.02% (BTD4) and 5.36% (BTD3), compared to as-cast devices.
• Improved exciton dissociation and more balanced charge transport were observed in TSA-treated devices.

Conclusions:

• The developed benzothiadiazole materials are effective for organic solar cells.
• Two-step annealing is a crucial processing technique for optimizing device performance.
• These findings contribute to the advancement of efficient organic photovoltaic technologies.