An Acetylene-Linked 9,9 '-Bicarbazole-Based Hole-Transporting Material for Efficient Perovskite Solar Cells

A new hole-transporting material (XJ-05) based on a 9,9'-bicarbazole core and four acetylene-linked triphenylamine groups was designed and applied for perovskite solar cells (PSCs). Optical spectra, thermal stability, electrochemical properties, density functional theory calculations, hydrophobicity, hole mobility, hole transfer dynamics, and surface morphology of XJ-05 were evaluated and discussed. Planar n-i-p PSCs were fabricated using triple cation perovskite Cs-0.05(MA(0.17)FA(0.83))(0.95)Pb(I0.83Br0.17)(3) as the light-harvesting layer. The PSCs based on doped XJ-05 achieved a maximum power conversion efficiency (PCE) of 16.08%, which is comparable to that of PSCs based on state-of-the-art hole-transporting material, spiro-OMeTAD (17.55%). Unfortunately, the doped XJ-05-based cells showed inferior stability. Moreover, the dopant-free XJ-05-based devices showed a PCE up to 12.61% and retained 79.9% of their initial PCE under moisture after 260 h, which represent a much better stability than the spiro-OMeTAD-based ones.