Layer-by-Layer-Processed Ternary Organic Solar Cells Using Perylene Bisimide as a Morphology-Inducing Component.

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) require precise control over the active layer morphology for optimal performance.
• Polythieno[3,4-b]-thiophene/benzodithiophene (PTB7) blended with PC71BM is a common active layer material in OSCs.
• The morphology of the PTB7:PC71BM blend significantly impacts charge generation and transport.

Purpose of the Study:

• To investigate the effect of a morphology-inducing layer on the performance of PTB7:PC71BM based organic solar cells.
• To enhance domain size and phase separation in the active layer through controlled self-aggregation.
• To improve the power conversion efficiency (PCE) of organic solar cells.

Main Methods:

• Fabrication of an underlying morphology-inducing layer using perylene bisimide (PBI-C4) and polythieno[3,4-b]-thiophene (PTB7).
• Spin-coating of the PTB7:PC71BM active layer onto the preprocessed morphology-inducing layer.
• Characterization of the active layer morphology, including domain size and phase separation.
• Device fabrication with conventional ZnO and novel photoconductive (ZnO:PBI-H) cathode interlayers.

Main Results:

• The morphology-inducing layer enhanced domain size and phase separation of the PTB7:PC71BM active layer compared to direct spin-coating on ZnO.
• A 14% improvement in power conversion efficiency (PCE) was observed, reaching 8.96% from 7.85%.
• Replacing the ZnO interlayer with a photoconductive ZnO:PBI-H interlayer resulted in a maximum PCE of 9.47%.

Conclusions:

• Perylene bisimide (PBI-C4) effectively induces favorable morphology in PTB7:PC71BM blends for organic solar cells.
• Controlled morphology significantly enhances the electrical properties and PCE of the devices.
• The development of a photoconductive interlayer offers a promising pathway for achieving state-of-the-art performance in PTB7:PC71BM based OSCs.