Surprisingly High Conductivity and Efficient Exciton Blocking in Fullerene/Wide-Energy-Gap Small Molecule Mixtures

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• 作者：Kevin J. Bergemann ; Jojo A. Amonoo ; Byeongseop Song ; Peter F. Green ; Stephen R. Forrest
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：June 10, 2015
• 年：2015
• 卷：15
• 期：6
• 页码：3994-3999
• 全文大小：321K
• ISSN：1530-6992

文摘

We find that mixtures of C₆₀ with the wide energy gap, small molecular weight semiconductor bathophenanthroline (BPhen) exhibit a combination of surprisingly high electron conductivity and efficient exciton blocking when employed as buffer layers in organic photovoltaic cells. Photoluminescence quenching measurements show that a 1:1 BPhen/C₆₀ mixed layer has an exciton blocking efficiency of 84 卤 5% compared to that of 100% for a neat BPhen layer. This high blocking efficiency is accompanied by a 100-fold increase in electron conductivity compared with neat BPhen. Transient photocurrent measurements show that charge transport through a neat BPhen buffer is dispersive, in contrast to nondispersive transport in the compound buffer. Interestingly, although the conductivity is high, there is no clearly defined insulating-to-conducting phase transition with increased insulating BPhen fraction. Thus, we infer that C₆₀ undergoes nanoscale (<10 nm domain size) phase segregation even at very high (>80%) BPhen fractions.