12-Oct-2022: Talk by Dr. Carlo A. R. Perini
Halide perovskite photovoltaics: tailoring interfaces to maximize the energy yield.
Metal Halide Perovskite (MHP) solar cells reach conversion efficiencies of light into electric power of 25.2% in single junctions, which is at par with the best performing silicon photovoltaics. Such performances are enabled using simple deposition methods from inks and low purity, cheap, abundant material precursors. Differently from traditional semiconductors, MHPs chemical compositions can be easily tuned, changing the optoelectronic properties of the material. These unique features have major relevance for photovoltaics, and could enable overcoming the limits of the inorganic semiconductors used to date. The major hindrances to market deployment of MHP technology are the limited device lifetime (stability), and the deposition methods commonly used, which are difficult to adopt at industrial level. Recently, surface treatments of MHP with small molecules of organo-halide salts have been shown effective in enhancing the efficiency of MHP devices. Despite promising results, the thermal stability of the treated interfaces is still debated. In this contribution we will provide an in-depth analysis of the structural and chemical changes happening at the interfaces modified with organo-halide salts under thermal stress. We will show how the deposition methods commonly used to perform these treatments result in lack of control on the structure and composition of the interface, and how this can result in loss of performances when the devices are exposed to thermal stress, limiting the energy yield (a parameter that is the product of lifetime and power conversion efficiency). We then propose an alternative route, based on thermal evaporation, which can be scaled up and enables control on the thickness and uniformity of the interface layer, enhancing both the efficiency and the stability of the solar cell stack.