Strong Band Gap Blueshift in Copper (I) Oxide Semiconductor via Bioinspired Route

Abstract

Semiconductors have numerous applications in both science and technology. Several methods have been developed to engineer their band gap, which is one of the most important parameters of semiconductors. Here, it is shown that the incorporation of various amino acids into the crystal lattice of copper (I) oxide, akin to the way living organisms incorporate organic macromolecules into minerals during biomineralization, leads to significant shrinkage in the volume of the host unit cell and a strong blueshift in the band gap of up to ≈18%. In examining the potential location of the bio‐organic molecules within the inorganic host's lattice, a very good fit between the proposed model of incorporation and experimental findings is found. The bioinspired phenomenon of band gap widening is thought to be attributable to the void‐induced quantum confinement effect, even though observed in micrometer‐sized crystals. This hypothesis is supported by developing a tight‐binding model that is found to fit well with the experimental data. The outcome of this research could profoundly impact the fields of light‐emitting and spin‐based devices as well as opens up a new bioinspired route to tune the band gap of semiconductors.

Bio-Inspired Molecular Bridging in a Hybrid Perovskite Leads to Enhanced Stability and Tunable Properties

“…From Figure 1 (and Table S1) it is evident that by far the highest distortions are induced by Lys, indicating that this amino acid induces the most pronounced effect. [68,70,71] Moreover, it is clear that incorporation of the other amino acids was lower, and was at approximately the same level in both growing routes. Since the effect of Lys on the MAPbBr3 lattice was significantly higher, especially via the slow growth procedure, we focused in this work on the study of Lys incorporation.…”

“…The fact that the incorporation of Lys induces higher lattice distortions than those of any of the other amino acids, combined with the effect of lattice parameter reduction, suggests the following incorporation mechanism: the two NH3+ groups of Lys probably replace two MA+ anions in the MAPbBr3 crystal, similarly to the replacement of carbonate groups in calcite by the COO− group of Asp, [69] and of Cu2+ in Cu2O. [71] In the case of MAPbBr3 the Lys backbone acts as a "molecular bridge" that tightens the atoms together, thereby decreasing the lattice parameter and leading to the reduction in microstrain fluctuations (Figure 2b,c). This bridging effect induces changes in MAPbBr3 thermal expansion coefficient as well as in its C-T transformation temperature.…”

“…Zinc oxide (ZnO, wurtzite) and copper oxide (Cu2O, cuprite) were also shown to be capable of hosting individual amino acids. [70,71] For ZnO the effect of the incorporation is similar to that of calcite; in both cases the unit cell expands, and there are changes in crystal morphology. [70] In contrast, incorporation of amino acids into Cu2O causes shrinkage of its unit cell, owing to substitution of the Cu+2 by the amine moiety of the amino acid.…”

“…[70] In contrast, incorporation of amino acids into Cu2O causes shrinkage of its unit cell, owing to substitution of the Cu+2 by the amine moiety of the amino acid. [71] Interestingly, this incorporation induces an increase in the optical band gaps of both of the inorganic semiconductors. [70][71][72] This increase results from a quantum-size-like effect, in which localization of charge carriers is induced by dispersion of the insulating amino acids within the semiconducting matrix.…”

“…[71] Interestingly, this incorporation induces an increase in the optical band gaps of both of the inorganic semiconductors. [70][71][72] This increase results from a quantum-size-like effect, in which localization of charge carriers is induced by dispersion of the insulating amino acids within the semiconducting matrix. [72] In this study, our material of choice from the HOIP family is methylammonium lead bromide (MAPbBr3).…”