Cost-effective hole transporting material for stable and efficient perovskite solar cells with fill factors up to 82%Electronic supplementary information (ESI) available. See DOI: 10.1039/c7ta08053k

A new small molecule-based hole selective material (HSM), 4,4′,4′′-(7,7′,7′′-(5,5,10,10,15,15-hexahexyl-10,15-dihydro-5 H -diindeno[1,2- a :1′,2′- c ]fluorene-2,7,12-triyl)tris(2,3-dihydrothieno[3,4- b ][1,4]dioxine-7,5-diyl))tris( N , N -bis(4-methoxyphenyl)aniline) (TRUX-E-T), has been developed by a facile synthesis with reduced cost. The highest occupied molecular orbital energy level and lowest unoccupied molecular orbital energy level of TRUX-E-T are −5.10 and −2.50 eV, respectively, making it a suitable HSM for lead iodide perovskite solar cells. TRUX-E-T can be smoothly deposited onto perovskite layers, enabling efficient perovskite solar cells with thin TRUX-E-T layers (∼50 nm), which helps cut the unit cost of the HSL used in PVSCs to approximately one-fortieth (1/40) of 2,2′,7,7′-tetrakis ( N , N -di- p -methoxyphenylamino)-9,9′-spirobifluorene (spiro-OMeTAD). Additionally, TRUX-E-T exhibits hole mobilities as high as 2.47 × 10 −4 cm 2 V −1 s −1 , better than spiro-OMeTAD. As a result, our perovskite solar cells using TRUX-E-T have shown high fill factors up to 82%. The champion cell achieved a maximum power conversion efficiency of 18.35% (16.44%) when measured under reverse (forward) voltage scan under AM1.5 G 100 mW cm −2 illumination. Our un-encapsulated cells exhibited good stability in ambient air, maintaining 96.4% of their initial efficiency of 18.35% after 20 days of storage. A cost-effective truxene-based hole selective material has been facilely synthesized for efficient perovskite solar cells with 82% FFs.