A Refined Bulk P-I-N Structure in All-Polymer Solar Cells To Achieve 20.1% Efficiency and Improved Stability

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• All-polymer solar cells (all-PSCs) offer promise for efficient and stable energy conversion.
• Precise control over the morphology of active layers in all-PSCs remains a significant challenge.
• Optimizing morphology is crucial for enhancing power conversion efficiency (PCE) and device longevity.

Purpose of the Study:

• To precisely control the morphology of the bulk p-i-n structure in all-PSCs.
• To improve energy-level alignment, exciton dissociation, and reduce energy loss.
• To enhance charge transport and suppress recombination for higher performance and stability.

Main Methods:

• Incorporation of a shamrock-shaped nonfullerene acceptor (AQI4) into a ternary formulation.
• Fabrication of thin films using a binary solvent system (chlorobenzene:o-xylene).
• Structural analysis to confirm reduced i-region width and optimized morphology.

Main Results:

• Optimized energy-level stairing and enhanced exciton dissociation were achieved.
• A high-density fibril network with reduced i-region width (< 2 nm) was formed.
• Organic solar cell (OSC) devices demonstrated a PCE of 20.1% (certified 19.5%) and a T₈₀ lifetime exceeding 1800 hours.

Conclusions:

• The shape of guest molecules, like AQI4, is key to modulating bulk p-i-n structure in all-PSCs.
• The binary solvent system facilitates efficient morphology control and printing fabrication.
• This approach significantly improves the performance and stability of all-polymer solar cells and modules.