MoO3 surface passivation of the transparent anode in organic solar cells using ultrathin films
MoO3 surface passivation of the transparent anode in organic solar cells using ultrathin films
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DOI：
10.1063/1.3077160
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发表时间：
2009-02-01
影响因子：
3.2
通讯作者：
Bernede, J. C.
中科院分区：
文献类型：
--
作者：
Cattin, L.;Dahou, F.;Bernede, J. C.
提出了一种新颖的有机太阳电池阳极材料铟锡氧化物(ITO)表面钝化工艺。我们证明，在ITO/有机施主界面处形成一层薄的MoO_3薄膜(3.5+/-1 nm)可以显著提高器件的性能。该器件是基于铜(CuPc)/富勒烯(C-60)/三(8-羟基喹啉)铝(Alq(3))的多异质结结构。MoO_3的沉积促进了CuPc向ITO的电荷转移。在氧化层的存在下，空穴收集效率的提高可以通过减少从CuPc到ITO阳极的空穴转移的有效势垒来解释。由于ITO/MoO_3/CuPc的功函数与CuPc的最高占据分子轨道之间的差异，ITO/MoO_3/CuPc的接触具有类似于金属-绝缘体-半导体(MIS)结构的特性，从而降低了势垒。结果表明，最佳的MoO_3厚度对应于最佳的ITO覆盖率和足够透明的梯形势垒之间的折衷，以实现载流子的隧穿。MoO_3薄膜是不连续的，当氧化物薄膜被超薄的金膜覆盖时，钝化效果得到改善。根据接触后的带状结构和几何考虑，讨论了这种行为。
An original surface passivation technique of indium tin oxide (ITO) used as anode in organic solar cells is proposed. We demonstrate that a thin MoO3 film (3.5 +/- 1 nm) at the interface ITO/organic donor allows improving significantly the devices' performances. The devices are based on the multiheterojunction structure copper phthalocyanine (CuPc)/fullerene (C-60)/aluminum tris(8-hydroxyquinoline) (Alq(3)). The deposition of MoO3 onto ITO improves the charge transfer from CuPc to ITO. The enhancement in the hole collection efficiency in the presence of an oxide layer can be explained in terms of the reduction in the effective barrier against hole transfer from CuPc into the ITO anode. The contact ITO/MoO3/CuPc behaves like a metal-insulator-semiconductor (MIS) structure, which allows reducing the energy barrier due to the difference between the work function of ITO and the highest occupied molecular orbital of CuPc. It is shown that the optimum MoO3 thickness corresponds to a compromise between an optimum ITO coverage and a sufficient transparency of the trapezoidal barrier for the tunneling of the charge carriers. The MoO3 thin films are discontinuous, and the passivation effect is improved when the oxide thin film is covered by an ultrathin gold film. Such behavior is discussed in the light of band scheme structures after contact and of geometrical considerations.