Semiconductor nanostructures for Photovoltaic applications
We study silicon based thin films (silicon sub-stoichiometric oxides and oxi-nitrides, amorphous and nanocrystalline) which find important applications as passivating layers in high efficiency Si based heterojunction solar cells. Good conductivity and low parasitic absorption are mandatory in order to improve solar cell efficiency. We study transport properties at the nano scale to understand the link between structural properties and conductivity, macroscopical transport and optical properties in order to clarify the physics of the passivation mechanisms. We study, in addition, innovative photovoltaic materials like perovskite nanocrystals which show very promising stability and high solar conversion efficiency.
Low dimensional III-Nitride alloys for high frequency electronics
III-Nitrides alloys (GaN, InGaN, AlGaN and AlInGaN) are widely used for several applications, such as High Electron Mobility Transistors (HEMT), solar cells, light emitting devices. These alloys show a bandgap tunable with composition, covering the whole visible spectrum; however, these materials suffer from the presence of structural defects emerging from strain and thermal relaxation phenomena. We study transport properties, optical spectra, electrical properties at macro and nano-scale and quantum confinement effects in order to clarify the role of material properties on device behaviour.
Methylammonium lead iodide perovskites
Methylammonium lead iodide perovskite (CH3NH3PbI3) has recently demonstrated to be a very interesting material for photovoltaic applications as well as for X-rays detection. Notwithstanding encouraging results in applications, perovskites still suffer from stability problems when used as transport layer in thin film solar cells, and one of the possible causes of the stability issue should be found in the presence of defects in the starting material. The aim of the study is to achieve a clear understanding of the role of defects on deterioration mechanisms of the final devices. We study defect states as a function of the compositional changes of the perovskite layers by electrical characterization methods (temperature dependent current-voltage and capacitance voltage analyses), charge spectroscopy techniques (Deep Level Transient Spectroscopy, Photo induced transient spectroscopy) and Surface Photovoltage Spectroscopy. Funding: POR-FESR EMILIA ROMAGNA 2014-2020, FORTRESS project, research unit CIRI-MAM.