Hole transport material, synthesis thereof, and solar cell

A compound having a structure comprising a substituted cyclopentadiene core flanked by four arylamine based moieties, having one of the formulas (I) and (II),

• wherein Z=—CH2—, or O or S or Se;
• wherein R1 is selected from C1-C20 linear or branched alkyl chains or alkoxy chains of formula
• where X=(CH2)nNRx3+M−;
• PRx3+M−;
• SO3Rx,
• where Rx is selected from C1-C20 linear or branched alkyl chains,
• where M− represents a counterion, and
• where n=0 to 20;
• wherein Ar1, Ar2, Ar3 and Ar4 are identical or different moieties selected from aromatic or heteroaromatic ring systems having one or more aromatic rings comprising 5 to 40 ring atoms and one or more of the atoms or groups independently selected from C, N, O, S, Se, SiR′2, or NR′ wherein R′ is selected from C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C4-C20 unsubstituted and substituted aryl, and C1-C20 fluoroalkyl group, wherein said alkyl, alkenyl, alkynyl, and fluoroalkyl, if they comprise 3 or more carbons may be linear, branched or cyclic;
• and
• wherein Arn1-Arn2 (with n=1, 2, 3, or 4) are identical or different moieties selected from aromatic or heteroaromatic ring systems having one or more aromatic rings comprising 5 to 40 ring atoms and one or more of the atoms or groups independently selected from C, N, O, S, Se, SiR′2, or NR′, wherein R′ is selected from C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C4-C20 unsubstituted and substituted aryl, and C1-C20 fluoroalkyl group, wherein said alkyl, alkenyl, alkynyl, and fluoroalkyl, if they comprise 3 or more carbons may be linear, branched or cyclic.