A D-π-A1-π-A2 push-pull small molecule donor for solution processed bulk heterojunction organic solar cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Small molecules are crucial for developing efficient organic solar cells.
• Designing donor-acceptor architectures is key to optimizing photovoltaic performance.
• Benzothiadiazole (BTD), triphenylamine (TPA), and naphthalimide (NPI) are common building blocks.

Purpose of the Study:

• To synthesize and characterize a novel D-π-A1-π-A2 small molecule for organic solar cells.
• To investigate the effect of two-step annealing (TSA) on the performance of organic solar cells based on the synthesized molecule.
• To understand the structure-property relationships influencing device efficiency.

Main Methods:

• Synthesis of a D-π-A1-π-A2 small molecule incorporating BTD, TPA, and NPI moieties.
• Fabrication of bulk heterojunction small molecule solar cells using the synthesized molecule and PC71BM.
• Optimization of the active layer through two-step annealing (TSA) treatment.
• Characterization of photovoltaic properties, including power conversion efficiency (PCE), short-circuit current (Jsc), and fill factor (FF).
• Analysis of light harvesting efficiency, IPCE, and nanoscale morphology.

Main Results:

• A novel D-π-A1-π-A2 small molecule was successfully synthesized.
• Organic solar cells fabricated with the as-cast blend showed a PCE of 2.21%.
• TSA treatment significantly enhanced the PCE to 6.67% due to improved Jsc and FF.
• TSA improved light harvesting, charge collection, nanoscale morphology, and crystallinity.

Conclusions:

• The synthesized D-π-A1-π-A2 small molecule shows promise for organic solar cell applications.
• Two-step annealing is an effective strategy for enhancing the performance of these solar cells.
• Improved morphology and charge transport are critical for achieving high power conversion efficiencies.