Electronic structure evolution and energy level alignment at C60/4,4′-cyclohexylidenebis[N,N-bis(4-methylphenyl) benzenamine]/MoOx/indium tin oxide interfaces
Electronic structure evolution and energy level alignment at C60/4,4′-cyclohexylidenebis[N,N-bis(4-methylphenyl) benzenamine]/MoOx/indium tin oxide interfaces
复制标题
DOI：
10.1063/1.4873959
复制
发表时间：
2014-04-28
影响因子：
3.2
通讯作者：
Gao, Yongli
中科院分区：
文献类型：
--
作者：
Liu, Xiaoliang;Yi, Shijuan;Gao, Yongli
用紫外光电子能谱和逆光电子能谱研究了富勒烯(C-60)/4，4‘-环己基双[N，N-二(4-甲基苯基)苯甲胺](TAPC)/氧化钼(MoOx)/氧化铟锡界面的电子结构演化和能级排列。随着TAPC在MoOx上的沉积，由于TAPC向MoOx的电子转移，在TAPC/MoOx界面形成了1.58 eV的偶极。TAPC的最高占据分子轨道(HOMO)起始点被钉扎在费米能级附近，导致p掺杂区，从而增加了界面上的载流子浓度。TAPC中向下的能带弯曲和由此产生的内置场有利于空穴向TAPC/MoOx界面的转移。TAPC能级的刚性下移表明，界面上没有明显的界面化学。随后在TAPC上沉积了C-60，由于TAPC向C-60的电子转移，在C-60/TAPC异质结处观察到了0.27 eV的偶极。这导致了TAPC在C-60/TAPC界面附近HOMO的下降，从而进一步增强了TAPC的能带弯曲。在C-60中也观察到了能带弯曲行为，类似地在C-60薄膜中产生了内置场，并改善了电子从C-60/TAPC界面的转移。界面分析表明，基于C-60/TAPC的有机光伏电池最大开路电压有望达到1.5 eV。(C)2014 AIP出版有限责任公司。
The electronic structure evolution and energy level alignment have been investigated at interfaces comprising fullerene (C-60)/4,4'-cyclohexylidenebis[N, N-bis(4-methylphenyl) benzenamine] (TAPC)/molybdenum oxide (MoOx)/indium tin oxide with ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy. With deposition of TAPC upon MoOx, a dipole of 1.58 eV was formed at the TAPC/MoOx interface due to electron transfer from TAPC to MoOx. The highest occupied molecular orbital (HOMO) onset of TAPC was pinned closed to the Fermi level, leading to a p-doped region and thus increasing the carrier concentration at the very interface. The downward band bending and the resulting built-in field in TAPC were favorable for the hole transfer toward the TAPC/MoOx interface. The rigid downward shift of energy levels of TAPC indicated no significant interface chemistry at the interface. With subsequent deposition of C-60 on TAPC, a dipole of 0.27 eV was observed at the C-60/TAPC heterojunction due to the electron transfer from TAPC to C-60. This led to a drop of the HOMO of TAPC near the C-60/TAPC interface, and hence further enhanced the band bending in TAPC. The band bending behavior was also observed in C-60, similarly creating a built-in field in C-60 film and improving the electron transfer away from the C-60/TAPC interface. It can be deduced from the interface analysis that a promising maximum open circuit voltage of 1.5 eV is achievable in C-60/TAPC-based organic photovoltaic cells. (C) 2014 AIP Publishing LLC.