Effect of Fullerene Tris-adducts on the Photovoltaic Performance of P3HT:Fullerene Ternary Blends

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• 作者：Hyunbum Kang ; Ki-Hyun Kim ; Tae Eui Kang ; Chul-Hee Cho ; Sunhee Park ; Sung Cheol Yoon ; Bumjoon J. Kim
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2013
• 出版时间：May 22, 2013
• 年：2013
• 卷：5
• 期：10
• 页码：4401-4408
• 全文大小：434K
• 年卷期：v.5,no.10(May 22, 2013)
• ISSN：1944-8252

文摘

Fullerene tris-adducts have the potential of achieving high open-circuit voltages (V_OC) in bulk heterojunction (BHJ) polymer solar cells (PSCs), because their lowest unoccupied molecular orbital (LUMO) level is higher than those of fullerene mono- and bis-adducts. However, no successful examples of the use of fullerene tris-adducts as electron acceptors have been reported. Herein, we developed a ternary-blend approach for the use of fullerene tris-adducts to fully exploit the merit of their high LUMO level. The compound o-xylenyl C₆₀ tris-adduct (OXCTA) was used as a ternary acceptor in the model system of poly(3-hexylthiophene) (P3HT) as the electron donor and the two soluble fullerene acceptors of OXCTA and fullerene monoadduct (o-xylenyl C₆₀ monoadduct (OXCMA), phenyl C₆₁-butyric acid methyl ester (PCBM), or indene-C₆₀ monoadduct (ICMA)). To explore the effect of OXCTA in ternary-blend PSC devices, the photovoltaic behavior of the device was investigated in terms of the weight fraction of OXCTA (W_OXCTA). When W_OXCTA is small (<0.3), OXCTA can generate a synergistic bridging effect between P3HT and the fullerene monoadduct, leading to simultaneous enhancement in both V_OC and short-circuit current (J_SC). For example, the ternary PSC devices of P3HT:(OXCMA:OXCTA) with W_OXCTA of 0.1 and 0.3 exhibited power-conversion efficiencies (PCEs) of 3.91% and 3.96%, respectively, which were significantly higher than the 3.61% provided by the P3HT:OXCMA device. Interestingly, for W_OXCTA > 0.7, both V_OC and PCE of the ternary-blend PSCs exhibited nonlinear compositional dependence on W_OXCTA. We noted that the nonlinear compositional trend of P3HT:(OXCMA:OXCTA) was significantly different from that of P3HT:(OXCMA:o-xylenyl C₆₀ bis-adduct (OXCBA)) ternary-blend PSC devices. The fundamental reasons for the differences between the photovoltaic trends of the two different ternary-blend systems were investigated systemically by comparing their optical, electrical, and morphological properties.

Keywords:

fullerene tris-adducts; ternary-blend; polymer solar cell; bridging effect; trap-assisted recombination; charge trapping