Efficient Diketopyrrolopyrrole‐Based Small‐Molecule Bulk‐Heterojunction Solar Cells with Different Electron‐Donating End‐Groups |
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Authors: | Yu Jin Kim Jang Yeol Back Seul‐Ong Kim Chan‐Woo Jeon Prof. Chan Eon Park Prof. Yun‐Hi Kim |
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Affiliation: | 1. POSTECH Organic Electronics Laboratory, Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 790‐784 (Republic of Korea);2. School of Materials Science&Engineering and Research Institute for Green Energy Convergence, Technology (REGET), Gyeongsang National University, Jin‐ju, 660‐701 (Republic of Korea);3. Department of Chemistry and Research Institute of Natural Science, Gyeongsang National University, Jin‐ju, 660‐701 (Republic of Korea) |
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Abstract: | A series of small molecules that contained identical π‐spacers (ethyne), a central diketopyrrolopyrrole (DPP) unit, and different aromatic electron‐donating end‐groups were synthesized and used in organic solar cells (OSCs) to study the effect of electron‐donating groups on the device performance. The three compounds, DPP‐A‐Ph , DPP‐A‐Na , and DPP‐A‐An , possessed intense absorption bands that covered a wide range, from 350 to 750 nm, and relatively low HOMO energy levels, from ?5.50 to ?5.55 eV. DPP‐A‐An , which contained anthracene end‐groups, demonstrated a stronger absorbance and a higher hole mobility than DPP‐A‐Ph , which contained phenyl groups, and DPP‐A‐Na , which contained naphthalene units. The power‐conversion efficiencies (PCEs) of OSCs based on organic:PC71BM blends (1:1, w/w) with a processed DIO additive were 3.93 % for DPP‐A‐An , 3.02 % for DPP‐Na , and 2.26 % for DPP‐A‐Ph . These findings suggest that a DPP core that is functionalized with electron‐donating capping groups constitutes a promising new class of solution‐processable small molecules for OSC applications. |
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Keywords: | absorption alkynes conjugation cross‐coupling solar cells |
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