Solution-processed formamidinium lead iodide (FAPbI3) perovskite is entropically metastable, and it exhibits condition-induced crystal polymorphism. Under an ambient atmosphere, the photoactive black ?-FAPbI3 converts easily to photoinactive yellow ?-FAPbI3. This ? ? ? phase degradation further accelerated upon exposure high temperature/humidity, directly threatening performance stability of so...

The excited states of atomic anions in liquids are bound only by the polarization of the surrounding solvent. Thus, the electron-detachment process following excitation to one of these solvent-bound states, known as charge-transfer-to-solvent (CTTS) states, provides a useful probe of solvent structure and dynamics. These transitions and subsequent relaxation dynamics also are influenced by othe...

Former p~pers from this laboratory indicate that the penetration of a weak base, ammonia,* and of a strong base, guanidine, 2 is probably preceded by a chemical reaction with a constituent of the protoplasm. On the other hand the penetration of a weak acid, hydrogen sulfide, s appears to take place by simple diffusion of molecular hydrogen sulfide through the non-aqueous protoplasm. What is the...