During the last years, a new class of QD has been revealed, known as perovskite QD (PeQD). PeQDs have shown enhanced properties respect to classical chalcogenide QD such as: such as size-and composition dependent bandgap, large absorption coefficients and very high quantum yields. Indeed, PeQDs have been utilized in various electronic devices such as solar cells, LED and lasers showing improved performance. Despite their excellent optical properties, they suffer from a number of drawbacks that hamper their implementation in FRET-based architectures: photo-degradation, fast anion exchange and instability to water and heat. The first part of the project has been dedicated to the resolution of these problems. Solving the stability problem is also of crucial importance not only for their implementation in optoelectronic devices but also when exploring their intrinsic optoelectronic properties, which may require relatively long measurements in air and under the light. In this project, the encapsulation with an amorphous alumina (AlOx) matrix deposited by atomic layer deposition (ALD) was successfully implemented as an effective strategy to stabilize PeQDs of different composition and to avoid problems of anion migration. Specifically, a low-temperature ALD process for the deposition of AlOx on a PeQD thin film has been successfully developed. The AlOx matrix protects the PeQDs from oxygen and moisture in the air, confers them stability in water and prevents sintering, thus improving their stability at high temperature and under light exposure for hours. Additional to stability, ALD is beneficial in fabricating multi-layered QD cascade structures. These results have been published in a scientific publication and disseminated in various conferences.
In the second step to move towards the realization of the proposed device, the energy transfer distance dependence in PeQD bilayer structures and in PeQD/metal catalyst structure has been studied. Data not yet published by the candidate show that an efficient energy transfer is possible in such systems. Moreover in collaboration with a group in the Molecular Foundry (Berkeley) by means of advanced optical spectroscopies, an exciton diffusion length of 200 nm was measured for an ordered PeQD@AlOx monolayer suggesting that PeQD@AlOx nanocomposite are ideal candidate for the realization of the proposed device.
