Isomerized Dithienopyrazine-Based Solid Additive Enables Organic Solar Cells With 20.5% Efficiency.

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Solid additives are crucial for optimizing organic solar cells (OSCs) by controlling film morphology and photoactive layer aggregation.
• The chemical structure of additives significantly impacts their performance in OSCs.
• High power conversion efficiencies (PCEs) in OSCs depend on efficient charge transport and optimized morphology.

Purpose of the Study:

• To design and investigate two isomeric solid additives, syn-dithieno[2,3-b:3',2'-e]pyrazine (syn-DTPy) and anti-dithieno[2,3-b:2',3'-e]pyrazine (anti-DTPy), for enhancing OSC performance.
• To explore the isomer-dependent conformational effects on morphology control in OSCs.
• To establish structure-property relationships for designing advanced solid additives.

Main Methods:

• Synthesis of syn-DTPy and anti-DTPy isomeric additives.
• Incorporation of additives into the D18:L8-BO organic solar cell system.
• Characterization of film morphology, phase separation, and charge transport pathways.
• Performance evaluation of OSCs, including power conversion efficiency (PCE) and fill factor (FF).

Main Results:

• Anti-DTPy additive optimized phase separation and charge transport pathways through directional intermolecular interactions.
• OSCs incorporating anti-DTPy achieved a remarkable PCE of 20.5% and a high FF of 81.9%.
• A distinct isomer-dependent conformational effect was observed for morphology control.

Conclusions:

• Isomeric structure of solid additives plays a critical role in morphology control and OSC performance.
• Anti-DTPy demonstrates significant potential for advancing high-efficiency organic solar cells.
• The findings provide valuable insights for the rational design of novel solid additives for organic electronics.