Polymer/polymer blend solar cells improved by using high-molecular-weight fluorene-based copolymer as electron...

Area of Science:

• Organic electronics
• Polymer science
• Photovoltaics

Background:

• All-polymer solar cells (APSCs) offer tunable properties.
• Achieving high power conversion efficiency (PCE) in APSCs is challenging.
• Poly(3-hexylthiophene) (P3HT) and PF12TBT are common donor-acceptor materials.

Purpose of the Study:

• To investigate the effect of molecular weight of PF12TBT on the PCE of P3HT/PF12TBT solar cells.
• To understand the morphological and charge transport mechanisms influencing device performance.
• To achieve a record PCE for APSCs.

Main Methods:

• Fabrication of APSCs using P3HT and varying molecular weights of PF12TBT.
• Optimization of thermal annealing conditions.
• Characterization of blend morphology and charge transport properties.

Main Results:

• PCE increased from 1.9% to 2.7% with increasing PF12TBT molecular weight (Mw).
• High Mw PF12TBT maintained efficient charge generation at high annealing temperatures.
• Formation of interconnected PF12TBT domains and ordered P3HT chains facilitated charge transport.

Conclusions:

• High molecular weight PF12TBT is crucial for optimizing blend morphology in P3HT/PF12TBT solar cells.
• Thermal annealing of high Mw PF12TBT-based devices yields optimal morphology for charge generation and transport.
• This study reports the highest PCE achieved to date for an all-polymer solar cell.