Efficient Functional Compensation Layer Integrated with HTL for Improved Stability and Performance in Perovskite Solar Cells

Improving the interface characteristics between the hole-transport layer (HTL) and perovskite absorber layer is crucial for achieving maximum efficiency in inverted perovskite solar cells (PSCs). This paper presents an effective functional compensation layer (FCL) composed of benzothiophene derivatives, particularly 5-(trifluoromethyl)-1-benzothiophene-2-carboxylic acid (TFMBTA); this layer is introduced between the MeO-2PACz HTL and perovskite absorber layer to improve the interfacial characteristics between them. This FCL improves charge transfer, hole extraction, and perovskite deposition by improving the surface morphology of the HTL and optimizing the energy level alignment. The functional groups of TFMBTA effectively passivate perovskite defects. As a result, the introduction of the TFMBTA FCL markedly reduces non-radiative recombination at the interface between the HTL and perovskite layer. The MeO-2PACz-based PSCs with the FCL demonstrated an impressive peak power conversion efficiency of 23.85%, accompanied by substantially enhanced open-circuit voltage (Voc), fill factor (FF), and long-term stability. Similarly, introducing the TFMBTA FCL between the PEDOT:PSS HTL and the perovskite layer enhanced both the stability and efficiency of PSCs, demonstrating the universality of FCLs across different types of HTLs.