Functionalized Thienopyrazines on NiOx Film as Self-Assembled Monolayer for Efficient Tin-Perovskite Solar Cells Using a Two-Step Method

Three functionalized thienopyrazines (TPs), TP-MN (1), TP-CA (2), and TPT-MN (3) were designed and synthesized as self-assembled monolayers (SAMs) deposited on the NiOx film for tin-perovskite solar cells (TPSCs). Thermal, optical, electrochemical, morphological, crystallinity, hole mobility, and charge recombination properties, as well as DFT-derived energy levels with electrostatic surface potential mapping of these SAMs, have been thoroughly investigated and discussed. The structure of the TP-MN (1) single crystal was successfully grown and analyzed to support the uniform SAM produced on the ITO/NiOx substrate. When we used NiOx as HTM in TPSC, the device showed poor performance. To improve the efficiency of TPSC, we utilized a combination of new organic SAMs with NiOx as HTM, the TPSC device exhibited the highest PCE of 7.7 % for TP-MN (1). Hence, the designed NiOx/TP-MN (1) acts as a new model system for the development of efficient SAM-based TPSC. To the best of our knowledge, the combination of organic SAMs with anchoring CN/CN or CN/COOH groups and NiOx as HTM for TPSC has never been reported elsewhere. The TPSC device based on the NiOx/TP-MN bilayer exhibits great enduring stability for performance, retaining ~80 % of its original value for shelf storage over 4000 h.