Aqueous Processed All-Polymer Solar Cells with High Open-Circuit Voltage Based on Low-Cost Thiophene-Quinoxaline...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Commercialization of organic solar cells (OSCs) requires eco-friendly solution processing and low-cost synthesis of photoactive materials.
• Aqueous-processable polymer donors are limited, and existing ones have shallow highest occupied molecular orbital (HOMO) energy levels, hindering power conversion efficiency (PCE) increases.
• Deep HOMO energy levels are crucial for achieving high open-circuit voltage (VOC) in OSCs.

Purpose of the Study:

• To design and synthesize novel aqueous-processable polymer donors with deep HOMO energy levels for OSC applications.
• To investigate the impact of oligo(ethylene glycol) (OEG) side chains on polymer properties and performance in OSCs.
• To fabricate and characterize aqueous-processed all-polymer solar cells (aq-APSCs) using the new polymer donors.

Main Methods:

• Synthesis of two water/alcohol-processable polymer donors, P(Qx8O-T) and P(Qx8O-Se), featuring OEG side chains and deep HOMO energy levels (∼-5.4 eV).
• Cost-effective synthesis and purification of the polymers in a few steps.
• Theoretical calculations to understand the role of dielectric environment variations in band gap lowering.
• Fabrication of aq-APSCs using P(Qx8O-T) and a known acceptor polymer, P(NDIDEG-T).

Main Results:

• The synthesized polymers, P(Qx8O-T) and P(Qx8O-Se), exhibit deep HOMO energy levels, facilitating higher open-circuit voltage (VOC).
• Theoretical calculations revealed that OEG side chains influence band gap lowering through dielectric environmental variations.
• The aq-APSCs based on P(Qx8O-T) and P(NDIDEG-T) achieved a PCE of 2.27% and a VOC approaching 0.8 V, representing state-of-the-art performance for aq-APSCs.

Conclusions:

• The study successfully developed low-cost, aqueous-processable polymer donors with deep HOMO levels for efficient OSCs.
• The findings provide valuable insights for designing high-performance, eco-friendly polymer donors for aqueous-processable OSCs.
• The achieved high VOC in aq-APSCs demonstrates the potential of these materials for next-generation solar energy technologies.