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Title

2D Hybrid Germanium Iodide Perovskites

Alternative Title

2D Hybrid Germanium Iodide Perovskite Semiconductors

Author

Μανιδάκη, Δέσποινα

Abstract

In the past decade, the class of halide perovskite compounds of the chemical formula AMX3 (A = Cs +, CH3NH3 +, or HC(NH2) 2 +, M = Ge2 +, Sn2 +, Pb2 +, X = Cl, Br, I) have been investigated extensively, owing to their remarkable achievements as semiconductors in optoelectronic devices, primarily in photovoltaics. Since 2012, when the CH3NH3PbI3 perovskite was used as a light absorber in all solid-state photovoltaics, perovskite photovoltaics have leaped forward to an impressive 25.7% efficiency. Despite this major success, there are still significant drawbacks that need to be addressed when employing lead-containing perovskites, such as the devices' long-term instability and the toxicity of lead in the environment. Under this pretext, in this diploma thesis, the synthesis of a new class of halide perovskites was investigated in the form of the 2D perovskite homologous series with a general chemical formula (CH_3 (CH_2 )_3 NH_3 )_2 (CH_3 NH_3 )_(n-1) Ge_n I_(3n+1) (where n is an integer). The choice of this system was made on the grounds that i) the low dimensions offer greater stability due to the large fraction of nonpolar molecules that can repel water, and ii) that germanium has negligible toxicity. In addition, the presence of Ge gives a new feature in the perovskite structure by breaking inversion symmetry and thus producing polar perovskite crystal structures, making the compounds suitable for Non-Linear Optical (NLO) applications, particularly related to the second-harmonic generation (SHG). The as synthesized materials were characterized by single-crystal X-Ray diffraction to determine the crystal structure, whereas phase purity was checked using powder X-ray diffraction. The bulk materials were characterized by elemental analysis (using SEM/EDS), while the bandgap of the semiconducting materials was determined using optical diffuse reflectance measurements.

Language

Greek

Issue date

2022-02-24

Collection

School/Department--School of Sciences and Engineering--Department of Materials Science and Technology--Graduate theses

Type of Work--Graduate theses

Permanent Link

https://elocus.lib.uoc.gr//dlib/b/c/9/metadata-dlib-user1647103857-17942.tkl

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