We report on optical spectroscopy (photoluminescence and photoluminescence excitation) on twodimensional self-organized layers of (C6H5C2H4 − N H3)2P bI4 perovskite. Temperature and excitation power dependance of the optical spectra gives a new insight into the excitonic and phononic properties of this hybrid organic/inorganic semiconductor. In particular, exciton-phonon interaction is found to be more than one order of magnitude higher than in GaAs QWs. As a result, photoluminescence emission lines have to be interpreted in the framework of a polaron model. PACS numbers: Valid PACS appear hereOptical properties of soft materials have attracted much attention for years thanks to their potential applications in optoelectronics devices. In particular, these last years, an increasing number of studies are dedicated on hybrid organic-inorganic materials[1], due to the possibility of combining the properties both of inorganic materials (high mobility, electrical pumping, band engineering) and of organic materials (low cost technology, high luminescence quantum yield at room temperature). In this context, organic-inorganic perovkites, having a chemical formula (R − NH3) 2 MX 4 where R is an organic chain, M is a metal and X a halogen, represent a natural hybrid system. Such perovskites present a great flexibility in their optical properties: the spectral position of the excitonic transitions can be tailored by substituting different halides X [2, 3], the photoluminescence efficiency can be tailored by changing the organic part R [4]. This kind of perovskites has been studied both in the framework of fundamental studies [2,3,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24] and of applications in optoelectronic as the active material in a distributed feedback laser for example [25]. Recently the strong coupling regime between the perovskite exciton and the optical mode of a Pérot-Fabry microcavity has been demonstrated at room temperature in the UV range [5] and in the visible range [6,7]. The physical properties of these new polaritons have now to be investigated. In particular, the demonstration of polariton-polariton interactions which lead to polariton scattering would be a breakthrough for the physics of these new devices in the context of the low threshold polariton lasers [26,27,28]. To evaluate these possibilities, a good knowledge of the perovskite material electronic properties is needed. As an example, the energy of the phonons and the strength of the electron-phonon coupling will indicate whether an efficient relaxation of perovskite polaritons is conceivable. Additionally, the origin of the different perosvkite luminescence lines has to be clarified to improve the knowledge about the exciton which couples to the cavity mode. .In this paper, we report on the optical properties of a particular perovskite molecule, namely [bi-(phenethylammonium) tetraiodoplumbate]: (C 6 H 5 C 2 H 4 − N H 3 ) 2 − P bI 4 (named PEPI), absorbing and emitting in the green part of the visible range. Photoluminescence (PL) ...

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We focus here our attention on a particular family of 2D-layered and 3D hybrid perovskite molecular crystals, the mixed perovskites (C6H5-C2H4-NH3)2PbZ4(1-x)Y4x and (CH3-NH3)PbZ3(1-x)Y3x, where Z and Y are halogen ions such as I, Br, and Cl. Studying experimentally the disorder-induced effects on the optical properties of the 2D mixed layered materials, we demonstrate that they can be considered as pseudobinary alloys, exactly like Ga1-xAlxAs, Cd1-xHgxTe inorganic semiconductors, or previously reported 3D mixed hybrid perovskite compounds. 2D-layered and 3D hybrid perovskites afford similar continuous optical tunability at room temperature. Our theoretical analysis allows one to describe the influence of alloying on the excitonic properties of 2D-layered perovskite molecular crystals. This model is further refined by considering different Bohr radii for pure compounds. This study confirms that despite a large binding energy of several 100 meV, the 2D excitons present a Wannier character rather than a Frenkel character. The small inhomogeneous broadening previously reported in 3D hybrid compounds at low temperature is similarly consistent with the Wannier character of free excitons.