Towards Efficient and Stable Perovskite Solar Cells Employing Non-Hygroscopic F4-TCNQ doped TFB as Hole-Transporting Material
Designing an efficient and stable hole transport layer (HTL) material is one of the essential issues to improve the performance of the organic-inorganic perovskite solar cells (PSCs). Herein, for the first time, an efficient model of hole transport material (HTM) is demonstrated by optimized doping of the conjugated polymer known as TFB (Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl)diphenylamine)]) with non-hygroscopic p-type dopant F4-TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) for high-efficiency PSCs. The PSC with the F4-TCNQ doped TFB exhibits the best power conversion efficiency (PCE) of 17.46%, which surpasses that of the reference devices, i.e., 16.64 (LiTFSI+TBP-doped Spiro-OMeTAD as HTM) and 11.01% (LiTFSI+TBP-doped TFB as HTM). F4-TCNQ doped TFB was believed to favor an efficient charge and energy transfer between the perovskite and hole transport layer, and to reduce charge recombination as evidenced by steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL) analysis. Moreover, the hydrophobic nature of F4-TCNQ contributed to enhancing the stability of the device under an ambient condition with RH of 45%. The device herein reported maintained ca. 80% of its initial efficiency after 10 days, significantly superior to both LiTFSI + TBP-doped Spiro-OMeTAD (ca. 30%) and LiTFSI + TBP-doped TFB (ca. 10%) based counterparts. This simple, yet novel strategy paves the way for demonstrating a promising route for a wide range of highly efficient solar cells and other photovoltaic applications.