Production of chalcogenide based nanocomposite thin films and optoelectronic device application

Today, while n-type transparent conductive materials such as ITO and FTO have achieved the development that can be used in many commercial-level optoelectronic device applications, p-type transparent conductive thin-film materials with high performance have not been developed yet. Therefore, in this thesis, studies were carried out on the production of nanocomposite (CuS)x:(ZnS)1-x p-type transparent conductive thin films by using the thermal evaporation method. (CuS)x:(ZnS)1-x thin-films for different x values were grown on Si and glass substrates by thermal evaporation method from pellet sources prepared by mixing copper sulfide and zinc sulfide micro-powders at a certain rate. By X-ray diffraction analysis of these produced samples, it was determined that they consisted of nano-crystals of both compounds, and the crystal grain sizes in (CuS)0.49:(ZnS)0.51 changed between 30 and 86 nm. From the surface and cross-section images taken by FESEM analysis, it was determined that the surface was quite smooth and homogeneous, and the thickness was consistent with the values measured during production (~50 nm). Additionally, elemental compositions were determined by the EDS analysis performed during the FESEM analysis. XPS analysis was performed to examine the molecular structure and ionic states of the component elements, and the findings obtained from the XRD analysis were confirmed. By applying UV-Vis spectrophotometer measurements, it was determined that the optical transmittance of the films at 550 nm wavelength ranged between 65% and 83%, that is, they were quite transparent, and the energy band gap (Eg) values were calculated using the Tauc method. Electrical parameters were determined by means of Hall Effect measurements. In the (CuS)0.49:(ZnS)0.51 sample, a hole concentration of 5.24×1021 cm-3, mobility value of 1.69 cm2·V-1·s-1 and a very high p-type conductivity value of 1420 S/cm was measured. The reason for having such a high hole concentration was explained by its molecular analysis. In addition to all these, three Si-based photodiodes were produced from nanocomposite (CuS)x:(ZnS)1-x thin films. With the analyzes made from spectral photocurrent measurements, it was determined that it has responsivity and detectivity capabilities, which exceed most commercial-level photodiodes, with 11.4 A/W and 3.2×1013 Jones values, respectively. However, a rare EQE (quantum efficiency) value exceeding one hundred percent was obtained as 2.85×103% (for p-CZS49/n-Si).