Optoelectronic properties of low- symmetry semiconductors

Abstract

The physical properties of materials are strongly correlated to their crystal symmetries: inversion symmetry breaking is required for inducing ferroelectricity, and the absence of mirror symmetry leads to optical chirality. Ferroelectricity and chirality have been utilized or proposed in electronic and optical devices for memory, computing, and signal processing, but their interplay with semiconducting properties, including optical emission is rarely studied. In this dissertation, with low dimensional chalco-halides and halides as model systems, I reveal the roles of symmetry breaking on the optical and optoelectronic properties. It is found that in quasi one-dimensional ferroelectric semiconductor SbSI crystal, across the paraelectric-ferroelectric phase transition an abrupt change of its photoluminescence peak position presents, suggesting the important role of polarization in modifying the band structure of the material. By introducing mechanical strain, we are able to increase its Curie temperature from ~25 oC to ~80 oC. By designing a chiral/achiral hybrid heterostructure R-(+)- and S-(−)-1-(1-naphthyl)- ethylammonium lead bromide/CsPbBr3, I find that achiral component can be modified to have chiral luminescence due to the chiral filtering effect of the chiral component. Further, through the use of chiral molecules R- and S- cyclohexylethylamine, I discover a new ferroelectric chiral crystal R- and S- cyclohexylethylamine lead iodide that has been found to carry switchable photo-diode effect with enhanced circular dichroism. These works shed lights on the use of symmetry in engineering the ferroelectric and chiral properties of semiconducting materials.