Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Nanoscale. 2013 Oct 7;5(19):8934-9. doi: 10.1039/c3nr00611e. Epub 2013 Aug 19.
Graphene has been proposed as a promising transparent conducting electrode material in organic photovoltaic (OPV) solar cells to substitute the widely used indium tin oxide (ITO). Various studies have reported OPV devices with graphene electrodes showing comparable performances to ITO-based OPV cells. However, the fabrication reliability or device yield has not been widely discussed. In our investigation it was found that graphene-based OPVs tend to have much lower device yield than the ITO-based ones if similar fabrication processes are used. One possible reason could be due to the challenge faced in obtaining a uniform coating of PEDOT:PSS hole injection layer (HIL) on graphene. In fact, several attempts have been made to overcome this challenge. In this work, we report a facile method of solvent modification of PEDOT:PSS to achieve a homogeneous coating on graphene. A significant enhancement in the device yield was observed as compared to devices using normal aqueous solution based PEDOT:PSS; nevertheless, it was still only ∼50%. Further improvement was made by adding an additional electron blocking layer (EBL), molybdenum trioxide, after the coating of PEDOT:PSS. The observation in this work calls for further investigation to understand the role played by the HIL or EBL in graphene-based OPV devices.
石墨烯被提议作为一种有前途的透明导电电极材料，用于有机光伏（OPV）太阳能电池，以替代广泛使用的铟锡氧化物（ITO）。各种研究报告称，具有石墨烯电极的 OPV 器件表现出与基于 ITO 的 OPV 电池相当的性能。然而，制造可靠性或器件产量尚未得到广泛讨论。在我们的研究中发现，如果使用类似的制造工艺，基于石墨烯的 OPV 器件的器件产量往往比基于 ITO 的器件低得多。一个可能的原因是由于在石墨烯上获得均匀的 PEDOT:PSS 空穴注入层（HIL）涂层面临挑战。事实上，已经有几种方法来克服这一挑战。在这项工作中，我们报告了一种简单的方法来对 PEDOT:PSS 进行溶剂改性，以实现在石墨烯上的均匀涂层。与使用普通水性 PEDOT:PSS 的器件相比，器件的产量有了显著提高；然而，仍然只有约 50%。通过在 PEDOT:PSS 涂层后添加额外的电子阻挡层（EBL）三氧化钼，进一步提高了器件的产量。这项工作的观察结果需要进一步研究，以了解 HIL 或 EBL 在基于石墨烯的 OPV 器件中的作用。
