Unencapsulated organic solar cells are prone to severe performance losses in the presence of moisture. We present accelerated damp heat (85 oC/85% RH) studies and show that the hygroscopic hole-transporting PEDOT:PSS layer is the origin of device failure in the case of prototypical inverted solar cells. Complementary measurements unveil that under these conditions a decreased PEDOT:PSS work function along with areas of reduced electrical contact between active layer and hole-transport layer are the main factors for device degradation rather than a chemical reaction of water with the active layer. We further explore replacements for PEDOT:PSS and find that tungsten oxide (WO3) or phosphomolybdic acid (PMA) – materials that can be processed from benign solvents at room temperature – yield comparable performance as PEDOT:PSS and enhance the resilience of solar cells under damp heat. The stability trend follows the order PEDOT:PSS
Bibliographical noteKAUST Repository Item: Exported on 2023-05-18
Acknowledgements: The authors acknowledge funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 952911 (“BOOSTER”). Furthermore, the authors would like to thank Thomas Stockinger and the group of the Division of Soft Matter Physics within the Institute of Experimental Physics at Johannes Kepler University in Linz for providing access to and support with the LBIC measurements. The authors also acknowledge the ‘Solar Factory of the Future’ as part of the Energy Campus Nuremberg (EnCN), which is supported by the Bavarian State Government (FKZ 20.2-3410.5-4-5).
ASJC Scopus subject areas
- Materials Science(all)
- Condensed Matter Physics