Al-TiO₂ composite-modified single-layer graphene as an efficient transparent cathode for organic solar cells.
Al-TiO₂ composite-modified single-layer graphene as an efficient transparent cathode for organic solar cells.
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DOI：
10.1021/nn3058399
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发表时间：
2013-01
期刊：
影响因子：
17.1
通讯作者：
Di Zhang;Fengxian Xie;P. Lin;W. Choy
中科院分区：
文献类型：
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作者：
Di Zhang;Fengxian Xie;P. Lin;W. Choy
虽然在调整石墨烯的性质（表面润湿性，功函数对准和载流子传输）以实现有机太阳能电池（OSC）中的高效石墨烯阴极方面存在挑战，但我们提出并证明使用Al-TiO_2复合材料来修饰单层石墨烯作为OSC的高效阴极。为了揭示复合材料在解决上述挑战方面的贡献，复合材料中蒸发的铝纳米团簇通过同时实现两个作用而使石墨烯阴极受益：改善其表面润湿性以用于随后的TiO 2沉积和降低其功函数以提供更好的能量对准。为了解决与电荷传输相关的挑战，具有优异电子传输的溶液处理的TiO_2可以为石墨烯阴极提供电荷提取增强，这对高效器件至关重要。然而，对于诸如旋涂的方法在初始疏水的石墨烯上产生均匀的膜是众所周知的问题，即使具有改进的润湿性。通过这种方法得到的TiO_2的不期望的形态大大抑制了其在增强电荷提取方面的有效性。我们提出了一种自组装的方法来存款的解决方案处理的TiO ↓ [2]上的Al覆盖的石墨烯形成的Al-TiO ↓ [2]复合材料。与旋涂法相比，自组装法在石墨烯表面的涂层更均匀，厚度可控性更高。因此，在倒置OSC中用Al-TiO_2复合物改性的石墨烯阴极产生2.58%的增强的功率转换效率，这是先前报道的石墨烯阴极OSC的最佳效率（1.27%）的2倍，达到使用氧化铟锡的对照装置的约75%的性能。
While there are challenges in tuning the properties of graphene (surface wettability, work function alignment, and carrier transport) for realizing an efficient graphene cathode in organic solar cells (OSCs), we propose and demonstrate using an Al-TiO₂ composite to modify single-layer graphene as an efficient cathode for OSCs. To unveil the contributions of the composite in addressing the aforementioned challenges, the evaporated aluminum nanoclusters in the composite benefit the graphene cathode by simultaneously achieving two roles of improving its surface wettability for subsequent TiO₂ deposition and reducing its work function to offer better energy alignment. To address challenges related to charge transport, solution-processed TiO₂ with excellent electron transport can offer charge extraction enhancement to the graphene cathode, which is essential to efficient devices. However, it is a well-known issue for methods such as spin-coating to produce uniform films on the initially hydrophobic graphene, even with improved wettability. The undesirable morphology of TiO₂ by such methods considerably inhibits its effectiveness in enhancing charge extraction. We propose a self-assembly method to deposit the solution-processed TiO₂ on the Al-covered graphene for forming the Al-TiO₂ composite. Compared with spin-coating, the self-assembly method is found to achieve more uniform coating on the graphene surface, with highly controllable thickness. Consequently, the graphene cathode modified with the Al-TiO₂ composite in inverted OSCs gives rise to enhanced power conversion efficiency of 2.58%, which is 2-fold of the previously best reported efficiency (1.27%) for graphene cathode OSCs, reaching ∼75% performance of control devices using indium tin oxide.