Efficient diketopyrrolopyrrole-based small-molecule bulk-heterojunction solar cells with different electron-donating...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) are a promising renewable energy technology.
• Developing efficient and solution-processable organic semiconductors is crucial for OSC advancement.
• The electronic properties of small molecules significantly influence OSC performance.

Purpose of the Study:

• To synthesize and characterize novel small molecules for OSC applications.
• To investigate the impact of different aromatic electron-donating end-groups on device performance.
• To establish structure-property relationships for diketopyrrolopyrrole (DPP)-based organic semiconductors.

Main Methods:

• Synthesis of three DPP-based small molecules with identical ethyne spacers and varied aromatic end-groups (phenyl, naphthalene, anthracene).
• Characterization of optical and electrochemical properties, including absorption spectra and HOMO energy levels.
• Fabrication and testing of OSC devices using these small molecules blended with PC71BM and DIO additive.

Main Results:

• Synthesized compounds exhibited broad absorption bands (350-750 nm) and low HOMO levels (-5.50 to -5.55 eV).
• The DPP-A-An derivative (anthracene end-groups) showed superior absorbance and hole mobility compared to DPP-A-Ph (phenyl) and DPP-A-Na (naphthalene).
• OSCs based on DPP-A-An achieved a power conversion efficiency (PCE) of 3.93%, higher than DPP-A-Na (3.02%) and DPP-A-Ph (2.26%).

Conclusions:

• Aromatic electron-donating end-groups significantly influence the performance of DPP-based small molecules in OSCs.
• The DPP core functionalized with electron-donating capping groups represents a promising class of materials for solution-processable OSCs.
• Anthracene end-groups appear to be particularly beneficial for enhancing OSC performance in this molecular design.