Semitransparent Organic Solar Cells Enabled by a Sequentially Deposited Bilayer Structure

Area of Science:

• Materials Science
• Renewable Energy
• Organic Electronics

Background:

• Semitransparent organic solar cells (ST-OSCs) are key for building-integrated photovoltaics.
• Traditional ST-OSCs often use bulk heterojunction (BHJ) structures requiring complex morphology optimization.
• Achieving high power conversion efficiency (PCE) and average visible light transmittance (AVT) simultaneously in BHJ devices presents a significant challenge.

Purpose of the Study:

• To investigate a sequentially deposited bilayer structure as an alternative to BHJ in ST-OSCs.
• To evaluate the impact of layer thickness on device performance, specifically PCE and AVT.
• To compare the performance of bilayer ST-OSCs with traditional BHJ ST-OSCs.

Main Methods:

• Fabrication of ST-OSCs using a PTB7-Th/IEICO-4F material combination in both bilayer and BHJ configurations.
• Systematic variation of the acceptor (IEICO-4F) layer thickness in the bilayer structure.
• Characterization of device performance, including PCE and AVT.

Main Results:

• The bilayer structure simplifies device optimization compared to BHJ.
• Increasing IEICO-4F thickness in the bilayer structure enhanced PCE without significantly reducing AVT due to its weak visible light absorption.
• Bilayer ST-OSCs achieved a higher PCE (8.5%) than BHJ ST-OSCs (8.1%) at a similar AVT (around 21%).

Conclusions:

• The sequentially deposited bilayer structure offers an advantageous alternative to BHJ for ST-OSCs.
• This structure facilitates easier processing and improved performance trade-offs between PCE and AVT.
• Bilayer ST-OSCs demonstrate significant potential for high-performance, building-integrated photovoltaic applications.