Vertical Cavity Biexciton Lasing in 2D Dodecylammonium Lead Iodide Perovskites

Abstract

We investigate the many-body interactions of excited species in the quantum wells formed in DA 2 PbI 4 , and identify biexciton formation with a binding energy of 50 meV. Biexcitons (stable four-particle states formed from the interaction of two excitons) have been well studied in quantum well structures [11,12] and are of interest for lasing applications due to their intrinsic potential for reducing selfabsorption compared to conventional excitonic lasing schemes, for example in 3D or 2D-3D perovskites. As well as recent reports of wavelength-tunable amplified spontaneous emission (ASE) in 3D perovskites [13] and ASE in mixed 2D-3D perovskites [14] there have been previous reports of biexciton lasing at 16 K with high excitation densities. [15] Here we demonstrate biexciton lasing in cavities formed from this 2D perovskite above liquid nitrogen temperatures (125 K). We additionally observe emission from higher-lying energy states, which we attribute to the formation of more than one structural phase in the film. Films of DA 2 PbI 4 were spin-cast from solutions of dodecylammonium iodide and lead iodide onto glass as described previously. [16] The films are multicrystalline, and scanning electron microscope images suggest grain sizes in the range 1-10 µm (Figure S8, Supporting Information). We examine the multiexciton properties of DA 2 PbI 4 through a series of photon-intensity and temperature dependent photoluminescence (PL) measurements. We use the PL spectrum at low temperature for assignment of the species present. The film was excited at 3.10 eV with 200 fs laser pulses (1 kHz repetition rate), resulting in a peak carrier concentration of 9.6 × 10 19 cm −3. The time-integrated PL spectrum at 10 K is shown in Figure 1a. The Frenkel defects reported previously [16] are clearly seen around 2.0 eV (labelled F). There are four further emission peaks we have labelled XX (≈2.37 eV), X (≈2.42 eV-the main emission peak reported previously), X′X′ (≈2.53 eV) and X′ (≈2.58 eV). We identify X as the exciton emission of DA 2 PbI 4 and XX as the biexciton resulting from two X excitons coupling together, as will be shown below. The lifetimes of all species aside from the Frenkel defects were shorter than the 3 ns instrument response time of our intensified charge-coupled device (iCCD). The contribution of each species to the overall PL was determined by modeling the PL data as five independent Gaussian peaks for Layered Ruddlesden-Popper-type (2D) metal-halide perovskites exhibit markedly increased exciton binding energies, exceeding 150 meV, compared to their 3D counterparts. Many-body physics, enabled by Coulomb interactions, plays a strong role and raises the biexciton binding energy to 50 meV. Here, photoluminescence at a range of temperatures and carrier concentrations in thin films of the layered perovskite material (C 12 H 25 NH 3) 2 PbI 4 is reported. Biexcitons are directly observed up to a sample temperature of 225 K. An optical microcavity (comprising a distributed Bragg reflector and a metal mirror), with photo...

Bright magnetic dipole radiation from two-dimensional lead-halide perovskites

“…In contrast, p-polarized PL at both 520 nm and 540 nm are well-described by ED-only theory. While low-energy emission shoulders have been observed in conventional PL spectra of both inorganic and hybrid organic-inorganic perovskites, 11,15,17,[19][20][21][22]26,[45][46][47][48]50 none of these prior works examined the polarization and momentum dependence reported here. Note that this theory completely accounts for reabsorption effects by including the complex (uniaxial) refractive index ( Supplementary Fig.…”

“…27,[35][36][37][38][39][40][41] Namely, optical transitions are assumed to be completely described by the lowest-order term in a multipolar expansion of the Hamiltonian -the electric dipole (ED) interaction -as higherorder interactions are conventionally slow enough to be considered "forbidden". [42][43][44] Operating within this conventional framework, researchers have attempted to identify the origin of anomalous low-energy sideband features in 2D and 3D HOIPs, arriving at interpretations ranging from boundor bi-exciton emission [45][46][47][48] to strong phonon-carrier interactions, 16,17,19,19,21,49,50 and in other cases remaining utterly unexplained. 15 Recent evidence of more "exotic" and fundamentally interesting physics, such as strong Rashba and Dresselhaus couplings 51,52 and an unconventional exciton fine structure, 40,41,53 reflect the interplay of strong spin-orbit coupling, structural complexity, 54,55 and the possibility of significant dynamic symmetry-breaking mechanisms.…”

Observation of Two Thresholds Leading to Polariton Condensation in 2D Hybrid Perovskites

“…[29], where bi-exciton lasing is claimed. In particular, in Booker et al [33] manuscript, not only a clear narrowing of the emission linewidth with respect to the bare bi-exciton spectrum is not observed-that also exclude even an ASE signal-but also the authors does not provide any coherence measurement to support their claim. For these reasons, we suggest to interpret their observation as standard biexction photoluminescence filtered by an optical microcavity.…”

“…For these reasons, we suggest to interpret their observation as standard biexction photoluminescence filtered by an optical microcavity. [33].…”

Explaining observed stability of excitons in highly excited CdSe nanoplatelets

“…In particular, the study of the optical properties of excitons and biexcitons has received much attention in recent years, first in order to understand the underlying physics, and later towards possible new applications [16][17][18][19][20][21][22][23][24][25][26][27]. Of special interest are biexciton-mediated lasing applications, due to the benefits brought about by the characteristics of biexcitons such as low thresholds and room-temperature utilization as a result of enhanced Coulomb interactions in low dimensions [28][29][30][31][32][33][34][35][36][37][38][39]. Furthermore, ever since twodimensional materials became easily manufactured, for instance by chemical vapor deposition and colloidal selfassembled growth, they have been increasingly the object of study for the development of optoelectronic devices [40][41][42][43][44][45][46][47][48][49][50].…”