9,9 '-bifluorenylidene derivatives for applications in perovskite cells

The article presents two 9,9'-bifluorenylidene derivatives differing in the length of the alkoxy chain, which were applied as hole transporting materials (HTM) in perovskite solar cells with structure FTO/b-TiO2/m-TiO2/perovskite/HTM/Au. Additionally, the reference cells without HTM and based on spiro-MeOTAD (C81H68N4O8) as HTM were also prepared. The highest efficiency (7.33%), being higher compare to the reference cell (4.40%), was reached for compound with ethoxyl groups.