9-arylidene-9H-fluorene-containing polymers for high efficiency polymer solar cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Donor-acceptor (D-A) alternating polymers are crucial for organic solar cell development.
• Controlling polymer properties like molecular weight and substituent placement impacts device performance.

Purpose of the Study:

• To synthesize and evaluate 9-arylidene-9H-fluorene based D-A polymers (P1 and P2) for polymer solar cells (PSCs).
• To investigate the influence of polymer molecular weight and alkoxy chain positioning on photovoltaic performance.

Main Methods:

• Synthesis of high and low molecular weight P1 (HMW-P1, LMW-P1) and high molecular weight P2.
• Fabrication of PSCs using P1 or P2 blended with PC71BM.
• Optimization of fabrication conditions using additives like 1,8-diiodooctane (DIO).

Main Results:

• HMW-P1:PC71BM PSCs achieved a power conversion efficiency (PCE) of 6.26%, significantly outperforming LMW-P1:PC71BM PSCs (2.75% PCE).
• Addition of DIO improved HMW-P1:PC71BM PSC PCE to 6.52%.
• P2:PC71BM PSCs exhibited a lower PCE of 2.51%.

Conclusions:

• Polymer molecular weight is a critical factor for achieving high PCE in PSCs.
• The position of alkoxy substituents on the 9-arylidene-9H-fluorene unit strongly influences photovoltaic performance.
• Optimized polymer design is essential for efficient PSCs.