Towards a Goal of Self-Assembling Molecules as Hole Transport Layers for Perovskite-Silicon Tandem Solar Cells

Jann B Landgraf1,2,3, Yashika Gupta2,3, Patricia S C Schulze2, Stefan W Glunz1,2,3,4, Juliane Borchert1,2,3 1Cluster of Excellence livMatS @ FIT - Freiburg Center for Interactive Materials and Bioinspired Technologies, Freiburg, --, Germany /2Fraunhofer Institute for Solar Energy Systems (ISE), Freiburg, --, Germany /3Chair of Photovoltaic Energy Conversion, Department of Sustainable Systems Engineering (INATECH), University of Freiburg, Freiburg, --, Germany /4Freiburg Materials Research Center (FMF), Freiburg, --, Germany

Abstract  —  The interface engineering of perovskite-silicon tandem solar cells plays a crucial role on the way towards higher performance. Self-assembling molecules (SAMs) such as Me‑4PACz can in theory provide a nearly loss-less hole-selective contact. However, wettability issues occur and further investigations on the influence of various processing parameters on the quality of the SAM layer are needed. Here, we provide wettability improvements by implementation of an aluminum oxide nanoparticle layer between hole transport layer and perovskite. Furthermore, we compare SAM layers with an aqua plasma or UV/ozone surface treatment before SAM deposition, SAM layers deposited via spin coating or evaporation, and SAM layers washed or non-washed after SAM deposition. Contact angle and cyclic voltammetry measurements are used for SAM characterization and the electro-optical performance of tandem solar cells is tested as well. While the deposition technique only plays a minor role, the UV/ozone treatment and inclusion of a washing step led to improved solar cell performance.