Anionic Conjugated Polyelectrolyte as a Semiconducting Additive for Efficient and Stable Perovskite Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Perovskite solar cells (PSCs) face efficiency and stability challenges due to intrinsic defects.
• Existing defect passivation strategies often involve insulators, hindering charge transport.
• π-conjugated polyelectrolytes (CPEs) offer potential as semiconducting additives for simultaneous defect mitigation and charge transport.

Purpose of the Study:

• To investigate the efficacy of two CPEs, MPS2-TEA and PCPDTBT2-TMA, as direct defect passivation additives within the perovskite layer of PSCs.
• To compare the defect passivation capabilities and impact on photovoltaic performance of CPEs with varying electrical conductivity.
• To evaluate the long-term stability of PSCs incorporating these CPEs under operational stress.

Main Methods:

• Synthesis and characterization of MPS2-TEA and PCPDTBT2-TMA.
• Incorporation of CPEs as additives directly within the perovskite absorber layer.
• Secondary ion microscopy for distribution analysis.
• Spectroscopic techniques for defect passivation assessment.
• Fabrication and performance testing of PSC devices (small and large area).
• Long-term stability testing under continuous illumination and thermal stress.

Main Results:

• CPEs were found to distribute evenly within the perovskite layer.
• MPS2-TEA exhibited superior defect passivation compared to PCPDTBT2-TMA.
• PSCs with MPS2-TEA achieved power conversion efficiencies (PCEs) of 22.7% (0.135 cm²) and 20.0% (1 cm²).
• Devices with MPS2-TEA demonstrated excellent operational stability, retaining over 87.3% of initial PCE after 960 hours of illumination and 89% after 850 hours at 85 °C.

Conclusions:

• CPEs, particularly MPS2-TEA, are effective semiconducting additives for passivating defects in PSCs.
• The electrical conductivity and chemical structure of CPEs significantly influence their defect passivation ability.
• This approach offers a promising pathway to enhance both the efficiency and long-term stability of perovskite solar cells and related optoelectronic devices.