Formamidine and cesium-based quasi-two-dimensional perovskites as photovoltaic absorbers.

Formamidine (FA) and cesium (Cs) cations were introduced into quasi-two-dimensional (2D) perovskites as B site cations. The unique crystalline growth of the resulting (n-C6H13NH3)2FAPb2I7, which promotes charge transport in photovoltaic solar cells, was confirmed, as was the stability of this material. The photovoltaic properties of (n-C6H13NH3)2FAPb2I7 were found to be superior to those of other homologous quasi-2D perovskite compounds.

Nearly perfect triplet-triplet energy transfer from Wannier excitons to naphthalene in organic-inorganic hybrid quantum-well materials.

We report the observation of extremely efficient energy transfer (greater than 99%) in an organic-inorganic hybrid quantum-well structure consisting of perovskite-type lead bromide well layers and naphthalene-linked ammonium barrier layers. Time-resolved photoluminescence measurements confirm that the transfer is triplet-triplet Dexter-type energy transfer from Wannier excitons in the inorganic well to the triplet state of naphthalene molecules in the organic barrier. Using measurements in the 10-300 K temperature range, we also investigated the temperature dependence of the energy transfer.