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We report design principles of the thermal and redox properties of synthetically accessible spiro-based hole transport materials (HTMs) and show the relevance of these findings to high-performance perovskite solar cells (PSCs). The chemical modification of an asymmetric spiro[fluorene-9,9'-xanthene] core is amenable to selective placement of redox active triphenylamine (TPA) units.W etherefore leveraged computational techniques to investigate five HTMs bearing TPAgroups judiciously positioned about this asymmetric spiro core.Itwas determined that TPAg roups positioned about the conjugated fluorene moiety increase the free energy change for holeextraction from the perovskite layer,w hile TPAs about the xanthene unit govern the T g values.T he synergistic effects of these characteristics resulted in an HTM characterized by both al ow reduction potential ( % 0.7 Vv s. NHE) and ah igh T g value (> 125 8 8C) to yield adevice power conversion efficiency (PCE) of 20.8 %inaP SC.

A set of design principles for high mobility xanthene-based organic hole transport materials are elucidated by combining multiple scales of theoretical chemistry (from virtual screening to bulk simulation) with experimental synthesis and characterization.

A homologous set of dyes that differ only in the donor fragments, namely phenothiazine (PTZ) and triarylamine (TPA) units, were evaluated in dye-sensitized solar cells (DSSCs). The novel PTZ-based dye differs from the TPA-based dye in that it contains a sulfur bridge that planarizes two aromatic rings and enables higher dye loading and higher stability in the oxidized form. These positive features notwithstanding, the superior absorptivity of devices sensitized by TPA-based dyes resulted in significantly higher power conversion efficiencies (PCEs) than those sensitized by PTZ-based dyes.