A compound having a structure of Formula I is disclosed, where at least one of R1 and R2 that is ortho to a boron atom of Formula I comprises a structure selected from (9-carbazolyl)-carbazole, indolocarbazole, triphenylene, fluorene, dibenzothiophene, dibenzofuran, dibenzoselenophene, pyridine, pyrimidine, triazine, aza-triphenylene, aza-fluorene, aza-carbazole, aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene.