Stable biexcitons in two-dimensional metal-halide perovskites with strong dynamic lattice disorder
Félix Thouin, Stefanie Neutzner, Daniele Cortecchia, Vlad Alexandru Dragomir, Cesare Soci, Teddy Salim, Yeng Ming Lam, Richard Leonelli, Annamaria Petrozza, Ajay Ram Srimath Kandada, Carlos Silva
PHYSICAL REVIEW MATERIALS
With strongly bound and stable excitons at room temperature, single-layer, two-dimensional organic-inorganic hybrid perovskites are viable semiconductors for light-emitting quantum optoelectronics applications. In such a technological context, it is imperative to comprehensively explore all the factors --- chemical, electronic and structural --- that govern strong multi-exciton correlations. Here, by means of two-dimensional coherent spectroscopy, we examine excitonic many-body effects in pure,
... single-layer (PEA)_2PbI_4 (PEA = phenylethylammonium). We determine the binding energy of biexcitons --- correlated two-electron, two-hole quasiparticles --- to be 44 ± 5 meV at room temperature. The extraordinarily high values are similar to those reported in other strongly excitonic two-dimensional materials such as transition-metal dichalchogenides. Importantly, we show that this binding energy increases by ∼25% upon cooling to 5 K. Our work highlights the importance of multi-exciton correlations in this class of technologically promising, solution-processable materials, in spite of the strong effects of lattice fluctuations and dynamic disorder.