A low-cost spiro[fluorene-9,9′-xanthene]-based hole transport material for highly efficient solid-state dye-sensitized solar cells and perovskite solar cells

A low-cost spiro[fluorene-9,9′-xanthene]-based HTM termed <bold>X60</bold> showed high PCEs of 7.30% in ssDSCs and 19.84% in PSCs under one sun, respectively.