Efficient Electron Transport Layer Free Small-Molecule Organic Solar Cells with Superior Device Stability

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Electron transport layers (ETLs) improve organic solar cell performance but complicate fabrication and affect stability.
• Developing ETL-free organic solar cells is crucial for simpler, more stable devices.

Purpose of the Study:

• To design and synthesize a novel small-molecule electron donor for ETL-free organic solar cells.
• To evaluate the performance and stability of organic solar cells with and without ETLs using the new donor.

Main Methods:

• Synthesis of a new small-molecule electron donor (H31) with a thiophene-substituted benzodithiophene core and trialkylsilyl side chains.
• Fabrication of organic solar cells using blends of H31 and the electron acceptor Y6, with and without an ETL (PDINO).
• Performance and stability testing of the fabricated solar cells.

Main Results:

• The new small-molecule donor (H31) enabled organic solar cells with power conversion efficiencies exceeding 13%.
• Devices fabricated without an ETL showed comparable performance to those with an ETL.
• ETL-free devices exhibited superior shelf life compared to devices with an ETL.

Conclusions:

• Small-molecule donor-acceptor blends are promising for efficient, reproducible, and stable organic solar cells.
• Eliminating ETLs simplifies device architecture and enhances long-term stability.
• This work presents a viable pathway towards practical, high-performance organic solar cells without interlayers.