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Multivalent anions as universal latent electron donors
Nature ( IF 50.5 ) Pub Date : 2019-09-25 , DOI: 10.1038/s41586-019-1575-7
Cindy G Tang 1 , Mazlan Nur Syafiqah 2 , Qi-Mian Koh 2 , Chao Zhao 1 , Jamal Zaini 2 , Qiu-Jing Seah 2 , Michael J Cass 3 , Martin J Humphries 3 , Ilaria Grizzi 3 , Jeremy H Burroughes 3 , Rui-Qi Png 1 , Lay-Lay Chua 1, 2 , Peter K H Ho 1
Affiliation  

Electrodes with low work functions are required to efficiently inject electrons into semiconductor devices. However, when the work function drops below about 4 electronvolts, the electrode suffers oxidation in air, which prevents its fabrication in ambient conditions. Here we show that multivalent anions such as oxalate, carbonate and sulfite can act as powerful latent electron donors when dispersed as small ion clusters in a matrix, while retaining their ability to be processed in solution in ambient conditions. The anions in these clusters can even n-dope the semiconductor core of π-conjugated polyelectrolytes that have low electron affinities, through a ground-state doping mechanism that is further amplified by a hole-sensitized or photosensitized mechanism in the device. A theoretical analysis of donor levels of these anions reveals that they are favourably upshifted from ionic lattices by a decrease in the Coulomb stabilization of small ion clusters, and by irreversibility effects. We attain an ultralow effective work function of 2.4 electronvolts with the polyfluorene core. We realize high-performance, solution-processed, white-light-emitting diodes and organic solar cells using polymer electron injection layers with these universal anion donors, demonstrating a general approach to chemically designed and ambient-processed Ohmic electron contacts for semiconductor devices. Multivalent anions are found to be capable of electron-doping polymer semiconductors to realize conductive films with very low work functions, which enable efficient electron injection into materials with low electron affinity.

中文翻译:

多价阴离子作为通用潜在电子供体

需要具有低功函数的电极来有效地将电子注入半导体器件。然而,当功函数降至约 4 电子伏以下时,电极在空气中会发生氧化,这会阻止其在环境条件下制造。在这里,我们展示了草酸盐、碳酸盐和亚硫酸盐等多价阴离子在以小离子簇形式分散在基质中时可以充当强大的潜在电子供体,同时保持它们在环境条件下在溶液中处理的能力。这些簇中的阴离子甚至可以通过基态掺杂机制对具有低电子亲和力的 π 共轭聚电解质的半导体核心进行 n 掺杂,该机制通过器件中的空穴敏化或光敏机制进一步放大。对这些阴离子的供体水平的理论分析表明,通过小离子簇的库仑稳定性的降低和不可逆性效应,它们从离子晶格有利地上移。我们使用聚芴核获得了 2.4 电子伏特的超低有效功函数。我们使用聚合物电子注入层和这些通用阴离子供体实现了高性能、溶液处理的白光发光二极管和有机太阳能电池,展示了半导体器件化学设计和环境处理欧姆电子接触的通用方法。发现多价阴离子能够对聚合物半导体进行电子掺杂,以实现具有非常低功函数的导电薄膜,从而能够将电子有效地注入到具有低电子亲和力的材料中。
更新日期:2019-09-25
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