Self‐passivation of molecular n‐type doping during air exposure using a highly efficient air‐instable dopant
Self‐passivation of molecular n‐type doping during air exposure using a highly efficient air‐instable dopant
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使用高效空气不稳定掺杂剂在空气暴露期间进行分子 n 型掺杂的自钝化
DOI：
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
B. Lüssem
中科院分区：
文献类型：
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作者：
M. Tietze;Florian Wölzl;T. Menke;A. Fischer;M. Riede;K. Leo;B. Lüssem
与p掺杂剂相比，高效分子n掺杂剂由于其低电离势，在空气中容易降解，限制了掺杂功能有机器件的加工条件。在这篇论文中，我们研究了n掺杂四系（1,3,4,6,7,8 -六氢- 2H -嘧啶[1,2 - a]嘧啶）钨（II） （W2(hpp)4）和W2(hpp)4掺杂的C60层的纯膜的空气稳定性。我们发现，掺杂C60薄膜的初始电导率在空气暴露后下降5个数量级后，通过真空热退火可以恢复1/3。此外，我们通过紫外光电子能谱（UPS）和塞贝克测量表明，在空气暴露后，C60的费米能级向最低的未占据分子轨道（LUMO）移动，清楚地表明n掺杂守恒。我们通过电荷转移到具有更深能级的宿主材料时W2(hpp)4能级的下降来解释这些发现，从而促进了对空气中氧化的保护。因此，观察到的电导率的恢复可以理解为分子n掺杂的自钝化。因此，高效氮掺杂薄膜在功能有机器件中的应用是可行的，即使在制造过程中在环境条件下处理。
In contrast to p‐dopants, highly efficient molecular n‐dopants are prone to degradation in air due to their low ionization potentials, limiting the processing conditions of doped functional organic devices. In this contribution, we investigate the air‐stability of pure films of the n‐dopant tetrakis(1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidinato)ditungsten(II) ( W2(hpp)4 ) and of C60 layers doped by W2(hpp)4 . We find that 1/3 of the initial conductivity of the doped C60 thin films can be restored by thermal annealing in vacuum after a drop by 5 orders of magnitude upon air exposure. Furthermore, we show by ultraviolet photoelectron spectroscopy (UPS) and Seebeck measurements that the Fermi level shift toward the lowest unoccupied molecular orbital (LUMO) of C60 remains after air exposure, clearly indicating a conservation of n‐doping. We explain these findings by a down‐shift of the W2(hpp)4 energy levels upon charge‐transfer to a host material with deeper lying energy‐levels, facilitating a protection against oxidation in air. Consequently, the observed recovery of the conductivity can be understood in terms of a self‐passivation of the molecular n‐doping. Hence, an application of highly efficient n‐doped thin films in functional organic devices handled even under ambient conditions during fabrication is feasible.
影响因子：
3.2
作者：
Balocco, C.;Majewski, L. A.;Song, A. M.
通讯作者：
Song, A. M.