Dicyanodithioquinoline-Based Donor Polymers With Large Dipole Moments for Efficient Organic Solar Cells Exceeding 20%...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) face efficiency limitations.
• Developing efficient donor polymers is key to overcoming these bottlenecks.
• Exciton-vibration coupling and energy loss impact OSC performance.

Purpose of the Study:

• To introduce a novel acceptor unit, dicyanodithioquinoline (TQCN), for constructing high-performance polymeric donors.
• To investigate the effect of the TQCN unit on exciton-vibration coupling and energy loss mechanisms in OSCs.
• To achieve high power conversion efficiency (PCE) in binary and ternary OSC devices.

Main Methods:

• Synthesis of a new donor polymer, PCN7, incorporating the TQCN acceptor unit.
• Fabrication and characterization of PCN7/L8-BO binary and D18:PCN7/L8-BO ternary OSC devices.
• Theoretical calculations and experimental analysis to understand exciton dynamics and energy loss.

Main Results:

• PCN7-based binary OSCs achieved a PCE of 19.45% with an open-circuit voltage (V_OC) of 0.910 V and low non-radiative energy loss (ΔE₃) of 0.216 eV.
• The TQCN unit effectively suppressed exciton-vibration coupling, leading to reduced exciton reorganization energy and enhanced intermolecular interactions compared to PM6.
• Ternary devices (D18:PCN7/L8-BO) further improved efficiency to 20.06%, demonstrating excellent reproducibility across multiple batches.

Conclusions:

• The TQCN acceptor unit is a promising building block for designing high-performance donor polymers in OSCs.
• TQCN incorporation effectively minimizes energy loss mechanisms, particularly non-radiative recombination, by suppressing exciton-vibration coupling.
• This strategy offers a viable pathway to achieve both low energy loss and high PCE in next-generation organic solar cells.