Traditionally, the implementation of active materials in photonic integrated circuits (PICs) has been developed by using III-V semiconductors and glasses and ferroelectrics doped by rare earth ions. However, there is a cost-efficient alternative based on (nano)materials synthetized by colloidal chemistry techniques. The fabrication of solution-processed nanomaterials provides semiconductors with tailor-made optical properties (light emission, absorption, scattering, bandgap) that can be engineered during the synthesis. In addition, their colloidal nature allows a straightforward integration into any optical architecture by coating or printing techniques. In this context, all-inorganic CsPbX3 (with X = Cl, Br, I) perovskite nanocrystals (PNCs) have recently emerged as an outstanding material with fascinating optical properties, including a high efficiency of absorption, a quantum yield of emission exceeding 90 % at room temperature, a tunable band gap depending on chemical composition—or size and shape tuning—, and high nonlinear optical coefficients. Considering the aforementioned background, the project of this Ph.D. Thesis intends to harness the potential of PNCs as an active material for optoelectronics, from both the point of view of the fundamental science and the applications. A first research objective involves the fabrication of PNC-based photodetectors enhanced by a solid-state ligand-exchange procedure that yields a superior device performance via increased inter-mobility between the PNCs. In this first step, the technology to assemble bulk nanomaterials (thin films) from PNC building blocks is stablished. A second objective is focused on the fundamental physics behind the generation of optical gain in PNCs. This study allows to determine the physical mechanisms involved, and also to stablish the role of different excitonic species, to explain the stimulated emission in these nanocrystals. In particular, the presented investigations demonstrate that the amplified spontaneous emission (ASE) in these materials is generated by the recombination of single excitons, and that the threshold of optical gain is determined only by optical losses. In line with this research, a novel all-fiber hollow-core amplification device, prepared by filling the fiber with PNCs, is properly fabricated and characterized. This device demonstrates a thresholdless gain effect at room temperature that can be attributed to a third order non-linear optical mechanism achieved by strong modal confinement. Finally, in order to further exploit the modal confinement strategy, layers of PNCs are integrated in a waveguide structure that was properly designed to enhance the generation of photoluminescence (PL) when the structure is optically pumped. In particular, this configuration was chosen to study the propagation of the secondary flow of photons resulting from the reabsorption of the PL. This effect, the photon recycling, results in spectral redshift and increased lifetimes for the photons extracted from the output of the waveguide. The photon recycling effect has important implications in the performance of solar cells, light-emitting diodes, among other optoelectronic devices. Considering the aforementioned results, this Ph. D. Thesis concludes that colloidal PNCs are promising candidates to pave the road towards a new generation of active optoelectronic devices.
