Anode Engineering with pH-Neutral Conjugated Polyelectrolyte Enabling Over 19% Efficiency in Organic Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Effective hole-transporting layers (HTLs) are crucial for organic solar cell (OSC) performance.
• Current HTLs often require substantial acid for doping, leading to material degradation and corrosion.
• Developing acid-free HTLs is essential for stable and efficient OSCs.

Purpose of the Study:

• To design and synthesize novel conjugated polyelectrolytes (CPEs) as efficient, acid-free HTLs.
• To investigate the impact of molecular conformation optimization on HTL properties.
• To demonstrate the potential of CPEs in high-performance organic electronic devices.

Main Methods:

• Synthesis of two CPEs (PEP-BT) with optimized molecular conformation and planar backbone.
• Doping of PEP-BT with polyoxometalate (POM4) to create PEP-BT:POM4.
• Characterization of molecular arrangement and π-π stacking distances.
• Fabrication and testing of OSCs and organic light-emitting diodes (OLEDs) using PEP-BT:POM4 as HTL.

Main Results:

• PEP-BT:POM4 exhibited enhanced doping and highly ordered molecular arrangement with reduced π-π stacking (3.85 Å).
• OSCs utilizing PEP-BT:POM4 as HTL achieved a record photovoltaic efficiency of 19.16%.
• OLEDs incorporating PEP-BT:POM4 showed improved luminous efficiency and a reduced turn-on voltage (0.4 V).

Conclusions:

• Optimized CPEs, like PEP-BT:POM4, serve as high-performance, acid-free HTLs.
• CPE-based HTLs can surpass 19% efficiency in OSCs, overcoming previous limitations.
• This work highlights the significant potential of CPEs for next-generation organic electronics.