Inclusion of Piperidine Side-Chain in Cathode Interlayer Materials Toward Improved Stability in Organic Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) show promise with high power conversion efficiencies (PCE) over 20%.
• Device lifetime is limited by material and film instabilities in active and interfacial layers.
• Current cathode interlayer (CIL) materials face challenges in optimizing OSC performance and stability.

Purpose of the Study:

• To design and synthesize novel CIL materials for improved OSC stability and efficiency.
• To investigate the impact of modifying CIL side-chain structure on OSC performance.
• To explore the influence of terminal group electron-withdrawing ability on CIL properties and device outcomes.

Main Methods:

• Synthesis of a new CIL material, NDI-N-P, featuring a piperidine cyclic amine side-chain.
• Fabrication of OSC devices utilizing the novel NDI-N-P CIL.
• Characterization of device performance, including PCE and long-term stability.
• Synthesis and investigation of a second CIL, NDI-I-P, with tailored aryl terminal groups.

Main Results:

• OSC devices with NDI-N-P achieved a PCE of 19.8% and demonstrated enhanced long-term stability.
• Replacing linear amine side-chains with piperidine mitigated negative effects on the active layer acceptor.
• Tailoring aryl terminal groups provided insights into self-doping effects and device performance.

Conclusions:

• Tailoring the local structure of CILs is a viable strategy for developing highly efficient and stable OSCs.
• The NDI-N-P material shows significant potential for advancing OSC technology.
• Further research into CIL properties can lead to enhanced electron extraction and improved OSC performance.