Pressure-Modulated Molecular Stacking Strategy Extends Exciton Diffusion Length for Thick-Film (300 nm) Organic...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Thick-film organic solar cells (OSCs) are promising for industrial production due to their scalability.
• Short exciton diffusion lengths (L_D) in organic semiconductors limit performance in thick-film OSCs, particularly open-circuit voltage and fill factor.
• Optimizing donor/acceptor (D/A) domain morphology is crucial for efficient charge generation and transport.

Purpose of the Study:

• To investigate a pressure-modulated molecular stacking (PMMS) strategy for enhancing crystallization and morphology in thick-film OSCs.
• To improve exciton diffusion length (L_D) and facilitate efficient exciton diffusion and carrier transport.
• To achieve high power conversion efficiencies (PCE) in large-area, thick-film OSCs.

Main Methods:

• Employed a pressure-modulated molecular stacking (PMMS) strategy to control imprinting pressure.
• Regulated fluid confinement depth and D/A inter-penetration to optimize vertical phase separation morphology.
• Fabricated thick-film OSCs using blade-coating technology with D18/BTP-eC9:L8-BO ternary system.

Main Results:

• Significantly extended exciton diffusion length (L_D) from approximately 26.5 nm to 40.3 nm.
• Achieved high power conversion efficiencies (PCE) of 20.20% for 100 nm devices and 19.27% for 300 nm devices.
• Demonstrated a large-area module (16.94 cm²) with an impressive PCE of 17.01%.

Conclusions:

• The PMMS strategy effectively enhances molecular stacking and vertical phase separation morphology in thick-film OSCs.
• Extended L_D facilitates efficient exciton diffusion and carrier transport, leading to improved photovoltaic performance.
• This approach offers a viable pathway for developing high-efficiency, large-scale thick-film organic solar cells.