Perovskite Semiconductors.

Metal halide perovskites, with general formula ABX3, consist in a continuous three-dimensional (3D) network of corner sharing metal halide octahedra, with the A cation enclosed in the cubooctahedral cavities. Here, A is a small organic or inorganic cation (e.g MA = methylammonium, Cs+), B is a divalent metallic cation (e.g. Pb2+, Sn2+), and X is a halide (Cl-, Br-, I-).

When bigger organic cations are used, low dimensional structures are created, enormously expanding the synthetic possibilities. For example, layered perovskites of the Ruddlesden-Popper series consist in the alternation of organic and inorganic layers allowing the creation two-dimensional (2D) multi quantum well-like structures.

Metal halide perovskite semiconductors possess a unique combination of optoelectronic properties, such as ambipolar carriers transport, high charge-carrier mobility,  high room temperature photoluminescence quantum yield at high excitation density, long radiative recombination lifetime (up to hundreds of ns), sharp absorption edges and high absorption coefficient.

However, the low exciton binding energy and trap-mediated recombination of 3D perovskites strongly limit their photoluminescence quantum yield (PLQY) for light-emitting applications.

In this project will engineer advanced perovskite films with high photoluminescence yield, targeting films with mixed dimensionalities (2D/3D multidimensional systems) to obtain the perfect balance between efficient radiative recombination, long radiative lifetime and high mobility.

Photophysical characterization.

Material’s suitability for lasing will be assessed through:

  • Photophysical characterization (time resolved photoluminescence and ultrafast transient absorption) to evaluate excited state lifetime and the presence of energy transfer
  • Vibrational and electronic spectroscopy to verify structure/property relationships
  • Charge transport studies in diode and transistor architectures
  • Evaluation of gain characteristics by studying amplified spontaneous emission in perovskite slab waveguides
  • Lasing in planar microcavities, vertical cavity surface-emitting lasers (VCSEL) and distributed optical feedback structures (DFB), where a periodic grating structure is combined with the perovskite film to provide high Q-factor and excellent control of spatial and spectral characteristics of the laser beam.

Electroluminescent devices.

After selecting materials with best transport and luminescence properties, the following objectives will be targeted:

  • Realization of high efficiency and high brightness light emitting diodes (LEDs) and light emitting field effect transistors (LE-FETs)
  • Minimization of optical losses due to the contact with the electrodes
  • Integration of the optical resonator in the planar or multi-layer vertical device structure - Efficient thermal management
  • Realization of the electrically injected perovskite laser, characterization of the fundamental lasing parameters and of the photophysical processes occurring in operational devices.