The work performed in SUPER involves:
- The design and synthesis of molecular building blocks. The templating cations are engineered in terms of: conjugated core, determining the main photophysical properties through control of the conjugation length extension, aromaticity and planarity; linker(s), including the positively charged tethering unit(s) defining the cation’s binding character; linear or ring-forming substituents, added for their electron withdrawing/donating character to promote n- and p-type conductivity, enhance electron delocalization, force molecular planarization, tune and enhance the luminescence yield, improve solubility and modulate the molecular association and crystal packing.
- The self-assembly of perovskite multi-quantum wells. SUPER targets layered perovskites of the Ruddlesden-Popper (L2An-1BnX3n+1) and Dion-Jacobson (LAn-1BnX3n+1) series, where X is a halide (F-, Cl-, Br-, I-), B is a divalent metal, n indicates the dimensionality connected to the thickness of the inorganic layers, A is a small organic cation (e.g. methylammonium) and L indicates a large mono or di-topic functional cation. SUPER aims to rationalize the effects of chemical composition on the perovskite’s connectivity, defectivity, rigidity and formation of related structural motifs. X-Ray duffraction and solid state NMR are used in combination to retrieve complementary structural informations. In particular, ssNMR is exploited to probe with high resolution the interatomic and intermolecular interactions, the local level of static and dynamic disorder as well as the presence of multiple phases and impurities, without stringent requirements in terms of sample crystallinity.
- The photophysical characterization of the perovskites. SUPER aims at the creation of a functional hybrid platform which can efficiently harness both the radiative excitonic recombination in the perovskite’s inorganic phase and the highly versatile luminescence of organic semiconductors. Optical spectroscopy is used to detrmine the type of internal energy level alignment of the quantum wells defining the photophysical properties of each type of heterojunction. SUPER further investigates how the crystal structure affects the optical properties of the material to establish close structural-properties correlations. The luminescence is investigated for both non-coherent and coherent light-emitting applications.
- The realization of electrically-driven light-emitting devices based on low-dimensional perovskites. The reduced transport properties coupled with the strong charge confinement in the inorganic wells of currently available low-dimensional perovskites represent a major unsolved challenge which blocks their effective exploitation and dramatically reduces their technological relevance. SUPER combines complementary strategies to greatly enhance the conductivity of MHP quantum wells and study their impact on charge transport at a fundamental level. Light-emitting field-effect transistors (LE-FETs) and light-emitting diodes (LEDs) are fabricated to study both the electrical transport and the electroluminescent properties of these low-dimensional semiconductors.
