Simple synthesis and molecular engineering of low-cost and star-shaped carbazole-based hole transporting materials for highly efficient perovskite solar cells

SGT-405 (3,6), developed by tuning the substitution position from (2,7) to (3,6) position of carbazole moiety, is an promising alternative non-spiro type small molecular HTM with low-cost, high T g and excellent performance for existing cost ineffective and synthetically-challenging spiro- OMeTAD in perovskite solar cells.