Organic hole-transporting materials (HTMs), AZO-I and AZO-II, were synthesized via Schiff base chemistry by functionalizing a phenothiazine core with triarylamine(s) through azomethine bridges. Substantial enhancements in the power conversion efficiency (PCE = 12.6% and 14% for AZO-I and AZO-II, respectively) and stability (68% or 91% of PCE retained after 60 days for AZO-I or AZO-II, respectively) of perovskite solar cells (PSCs) were achieved when switching from mono-(AZO-I) to disubstituted (AZO-II) HTMs. The extremely low production costs (9 and 12 $/g for AZO-I and AZO-II, respectively), together with the Pd-catalyst-free synthesis, make these materials excellent candidates for lowcost and eco-friendly PSCs.

The ring‐opening reaction of α‐hydroxycyclopenteno‐aziridines (6‐azabicyclo[3.1.0]hex‐3‐en‐2‐ols) was investigated in water and under physiological conditions (pH = 7.4) at 37 °C by using a range of carbon‐, oxygen‐, nitrogen‐, and sulfur‐containing nucleophiles such as azides, anilines, and thiols (aryl and alkyl thiols as well as cysteine and its derivatives), which provided the products in moderate to high isolated yields. The reactivity was also demonstrated in the bioconjugation of α‐hydroxycyclopenteno‐aziridine with the peptide hormone salmon calcitonin (sCT).