Band‐Edge Exciton Fine Structure and Exciton Recombination Dynamics in Single Crystals of Layered Hybrid Perovskites.

2D perovskite materials have recently reattracted intense research interest for applications in photovoltaics and optoelectronics. As a consequence of the dielectric and quantum confinement effect, they show strongly bound and stable excitons at room temperature. Here, the band‐edge exciton fine structure and in particular its exciton and biexciton dynamics in high quality crystals of (PEA)2PbI4 are investigated. A comparison of bulk and surface exciton lifetimes yields a room temperature surface recombination velocity of 2 × 103 cm s−1 and an intrinsic lifetime of 185 ns. Biexciton emission is evidenced at room temperature, with a binding energy of ≈45 meV and a lifetime of 80 ps. At low temperature, exciton state splitting is observed, which is caused by the electron–hole exchange interaction. Transient photoluminescence resolves the low‐lying dark exciton state, with a bright/dark splitting energy estimated to be 10 meV. This work contributes to the understanding of the complex scenario of the elementary photoexcitations in 2D perovskites. [ABSTRACT FROM AUTHOR]