Metal-halide perovskite for photoconversion: fabrication at ambient conditions and photoelectrochemical characterization

Abstract

As a result of the increasing worldwide energy demand and the environmental impacts resulting from the use of fossil fuels, the search for alternative energy resources is gaining more and more importance. In this context, among the different renewable energies, the field of photovoltaics has undergone rapid progress in the last few years due to the development of solar cells based on hybrid organic-inorganic halide perovskite materials. The natural abundance of the precursors employed to synthesise these materials and their excellent optoelectronic properties make them potential competitors of well-established thin-film photovoltaic technologies such as those based on silicon. However, perovskite solar cells have several fundamental issues such as the lack of longterm stability under environmental conditions (moisture, oxygen, heat and light), the requirement of expensive materials as contacts and technical limitations to their industrial scaling that restrict their widespread commercialisation. The main aim of this thesis is to provide a fundamental knowledge aimed at understanding the physicochemical processes that determine the stability and photovoltaic performance of perovskite solar devices. In particular, small perturbation optoelectronic techniques have been used to look at electronicionic processes that cause hysteresis phenomena. They have also been used to identify the main routes of charge recombination for different perovskite devices and under different moisture conditions. Regarding this, simple models for the interpretation of the different signals obtained from small perturbation techniques are also provided in this thesis. Another important contribution of this work refers to the preparation of perovskites under ambient conditions. Here we have found that the traditional use of relative humidity as control parameter to fabricate cells should be replaced by the absolute water amount in the atmosphere in the form of partial water vapour pressure. This last point opens a new window to facilitate the industrial implementation of perovskite solar cells because no glove box would limit the area of the devices.