"In the search for cost-effective solar cells, colloidal inorganic semiconducting nanocrystals (NCs) have received much interest due to their readily-tunable absorption across the visible/near-IR, their high absorption coefficients and photostability. Yet many state-of-the-art NCs for photovoltaics are either based on toxic compositions or scarce elements on earth. It thus becomes essential to develop new systems from environmentally benign and earth-abundant elements with strong absorption properties. This project identified a few potential candidates, namely FeS2, Cu2S, CuO and Cu2ZnSnS4, due to their low raw material cost, their suitable band gaps, their high absorption coefficients and the availability of NC synthetic protocols. Relatively little work has been done on applying these NCs in solution-processed solar cells compared to those from II-VI/IV-VI groups, the Cu(InGa)(SeS)2 and Si systems. Specifically, this project involves the following aspects:1. Optimization of synthetic methods for the above-mentioned NC systems.2. Functionalization of NC surfaces with difference ligands via ligand exchange.3. Realization of field-effect transistors based on NC thin films and investigation of the effects of NC size/morphology and ligands on charge transport.4. Realization and optimization of solar cells based on NCs or NC/organic hybrids by correlating the effects of different synthetic and ligand conditions, improvement in light harvesting by the tandem cell approach.It can be anticipated that, by developing solar cells based on these new NCs, this project will gain fundamental understandings on how different NC and surface properties can impact the charge dissociation, transport, and recombination processes. The Marie-Curie grant would also consolidate the current efforts of this applicant, establish her further in her research and provide the ideal platform for her to become internationally leading in the field of applying colloidal NCs in optoelectronics."