Sequential processing: control of nanomorphology in bulk heterojunction solar cells.

Area of Science:

• Materials Science
• Organic Electronics
• Renewable Energy

Background:

• Bulk heterojunction (BHJ) organic solar cells are promising for renewable energy.
• Achieving optimal nanomorphology is crucial for efficient charge transport.
• Conventional BHJ fabrication methods face challenges in controlling morphology.

Purpose of the Study:

• To investigate the fabrication of BHJ organic photovoltaic devices using a sequential solution deposition process.
• To explore the formation of a layer-evolved bulk heterojunction (LE-BHJ) nanomorphology.
• To evaluate the impact of LE-BHJ on device performance and nanomorphology.

Main Methods:

• Fabrication of poly[N-9''-hepta-decanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole) (PCDTBT)/[6,6]-phenyl C(70) butyric acid methyl ester (PC(70)BM) devices via sequential solution deposition.
• Utilizing a cosolvent in the top layer deposition to induce interdiffusion.
• Characterization of the resulting nanomorphology and device power conversion efficiency.

Main Results:

• Successful fabrication of PCDTBT:PC(70)BM BHJ organic photovoltaic devices through sequential solution deposition.
• Formation of an interdiffused structure with LE-BHJ nanomorphology due to PC(70)BM penetration.
• Optimized cosolvent ratio yielded LE-BHJ solar cells with power conversion efficiency comparable to conventional BHJ cells.
• The LE-BHJ nanomorphology exhibited superior vertical connectivity compared to conventional BHJ materials.

Conclusions:

• Sequential solution deposition is a viable method for fabricating efficient BHJ organic solar cells.
• The LE-BHJ nanomorphology offers advantages in charge transport due to improved vertical connectivity.
• This approach provides a pathway for developing high-performance organic photovoltaic devices.