Ultrafast charge transfer and coherent phonons in electroactive organic cation-templated low-dimensional perovskite analogues

Hybrid organic-inorganic perovskites (HOIPs) have emerged as promising materials for optoelectronic applications, yet gaining control over their structural and electronic tunability remains a key challenge. In this study, we introduce 7<i>H</i>-dibenzo[<i>c</i>,<i>g</i>]carbazole (DBCz) as a novel electroactive organic cation that enables the formation of two distinct low-dimensional hybrid metal halides: a conventional 2D perovskite structure, (DBCz)2PbI4, and a previously unreported layered perovskite analogue structure with edge-sharing octahedra, DBCzPbI3. The edge-sharing phase represents a new structural motif within the hybrid metal halide family. Both materials exhibit a type-II band alignment, facilitating ultrafast photoinduced hole transfer from the inorganic to the organic layer. Using transient absorption spectroscopy, we identify the formation of DBCz-based hole polarons in both phases, and uniquely observe the charge-transfer-induced formation of triplet states and room-temperature coherent phonons for the perovskite analogue phase. These findings highlight the role of molecular design in controlling excited-state dynamics and exciton-lattice interactions in hybrid metal halides.