Modulation of the interfacial contact via self-assembled molecule interlayer towards highly efficient and stable poly(3-hexylthiophene)-based perovskite solar cells

Metal halide perovskite solar cells (PSCs) are one of the most promising next-generation photovoltaic technologies. And one typical cell configuration is the n-i-p design, in which the hole transport layer (HTL) plays a critical role in determining the device's performance and stability. However, the commonly used 2,2′,7,7′-tetrakis[N,N-di(4methoxylphenyl)amino]-9,9′-spirobifluorene (Spiro-OMeTAD) needs hygroscopic and volatile dopants, limiting the long-term stability. Recently, Poly(3-hexylthiophene) (P3HT) has been widely investigated as the dopant-free HTL, attributed to its excellent electrical properties and chemical stability. However, the pristine P3HT film is hydrophobic and will form unsatisfying physical contact with the perovskite, resulting in severe charge recombination and poor device performance. Herein, an ultrathin layer of [2-(3,6-Dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic Acid (MeO-2PACz) is inserted at perovskite/P3HT interface. The MeO-2PACz interlayer can improve the P3HT film quality, enhance perovskite/P3HT interface contact, and reduce defects. Consequently, a power conversion efficiency of 21.37% is achieved for the MeO-2PACz-modified device. Without encapsulation, the modified device can retain 94.9% of the initial PCE after 1600 h of aging in the N2 environment.