Cattin Linda, Louarn Guy, Arzel Ludovic, Stephant Nicolas, Morsli Mustapha, Bernède Jean Christian
Institut des Matériaux Jean Rouxel, IMN, Université de Nantes, CNRS, Nantes F-44000, France.
Faculté des Sciences et des Techniques, Université de Nantes, 2 rue de la Houssinière, BP 92208, Nantes F-44000, France.
ACS Omega. 2021 Mar 2;6(10):6614-6622. doi: 10.1021/acsomega.0c05259. eCollection 2021 Mar 16.
In organic photovoltaic (OPV) cells, besides the organic active layer, the electron-transporting layer (ETL) has a primordial role in transporting electrons and blocking holes. In planar heterojunction-OPVs (PHJ-OPVs), the ETL is called the exciton blocking layer (EBL). The optimum thickness of the EBL is 9 nm. However, in the case of inverted OPVs, such thickness is too high to permit efficient electron collection, due to the fact that there is no possibility of metal diffusion in the EBL during the top metal electrode deposition. In the present work, we show that the introduction of a thin potassium layer between the indium tin oxide (ITO) cathode and the EBL increases dramatically the conductivity of the EBL. We demonstrate that K not only behaves as a simple ultrathin layer allowing for the discrimination of the charge carriers at the cathode/organic material interface but also by diffusing into the EBL, it increases its conductivity by 3 orders of magnitude, which allows us to improve the shape of the - characteristics and the PHJ-inverted OPV efficiency by more than 33%. Moreover, we also show that PHJ-inverted OPVs with K in their EBLs are more stable than those with Alq alone.
在有机光伏（OPV）电池中，除了有机活性层外，电子传输层（ETL）在传输电子和阻挡空穴方面起着至关重要的作用。在平面异质结有机光伏电池（PHJ - OPV）中，ETL被称为激子阻挡层（EBL）。EBL的最佳厚度为9纳米。然而，在倒置OPV的情况下，由于在顶部金属电极沉积过程中EBL中不存在金属扩散的可能性，这样的厚度过高以至于无法实现高效的电子收集。在本工作中，我们表明在氧化铟锡（ITO）阴极和EBL之间引入一层薄钾层会显著提高EBL的电导率。我们证明，钾不仅作为一个简单的超薄层，能够在阴极/有机材料界面区分电荷载流子，而且通过扩散到EBL中，它将EBL的电导率提高了三个数量级，这使我们能够将 - 特性的形状和PHJ倒置OPV的效率提高超过33%。此外，我们还表明，EBL中含有钾的PHJ倒置OPV比仅含有Alq的更稳定。
