BODIPY Cored A-D-A'-D-A Type Nonfused-Ring Electron Acceptor for Efficient Polymer Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Polymer solar cells (PSCs) require efficient non-fused-ring electron acceptors (NFREAs).
• Boron dipyrromethene (BODIPY) has not been previously utilized as a core component in NFREAs for PSCs.

Purpose of the Study:

• To synthesize and characterize a novel A-D-A'-D-A type NFREA using BODIPY as the electron-deficient core.
• To evaluate the performance of the new NFREA in PSCs and compare it with a BODIPY-free counterpart.

Main Methods:

• Synthesis of a novel NFREA, tMBCIC, featuring a BODIPY core flanked by cyclopentadithiophene (CPDT) and fluorinated dicyanoindanone (DFIC) units.
• Structural analysis revealing a twisted configuration due to the steric BODIPY core.
• Fabrication and characterization of PSCs using tMBCIC as the electron acceptor with PBDB-T as the donor.

Main Results:

• The BODIPY-cored tMBCIC exhibited reduced aggregation and weakened intramolecular interactions compared to a planar, BODIPY-free analog (bCIC).
• tMBCIC showed an up-shifted lowest unoccupied molecular orbital (LUMO) by 0.4 eV and a blueshifted absorption spectrum by up to 150 nm.
• PSCs utilizing tMBCIC achieved a superior power conversion efficiency (PCE) of 9.22% and an open-circuit voltage (V_oc) of 0.954 V, significantly outperforming bCIC-based devices (4.47% PCE, 0.739 V V_oc).

Conclusions:

• The incorporation of a BODIPY core into an A-D-A'-D-A NFREA structure is a viable strategy for enhancing PSC performance.
• The twisted molecular geometry induced by the BODIPY core effectively mitigates aggregation and optimizes electronic properties.
• The developed BODIPY-cored NFREA represents a significant advancement, achieving a remarkable PCE of 9.22% for PSCs.