Si Nanowires (NWs) have been commonly fabricated via expensive synthesis processes on particular substrates without some critical features such as mechanical flexibility and optical transparency. Lack of these features limit the applications in their potential research area. In this work, we demonstrated that ordered and disordered single crystalline silicon nanowires can be transferred from Si wafer onto a wide range of alien substrates while preserving their original order and alignment on the mother substrate. Vertically well-aligned Si NWs with different lengths and densities were successfully transferred on Ag-pre-coated glasses, transparent-conductive-oxides and metal foils (Cu), which enable ohmic contact formation between Si NWs and the employed substrates, which is essential for the fabrication of electronics and opto-electronics devices. This approach offers promise to construct low-cost device fabrication with highly crystalline semiconductor materials, which is a crucial step for the realization of next generation highly efficient core-shell solar cells. As an illustrative application, the transferred disordered Si NWs were then decorated with a thin layer of CZTS for the fabrication of a third generation solar cell, which has been exhibited the best power conversion efficiency so far in a device constructed with the same material combination.
In this work, three-dimensional (3-D) p-n junctions were formed for the fabrication of field ionization gas sensors and solar cells. P-Si micro-pillars/ZnO NWs, n-TiO2-nanorod/p-CdTe and n-Si-NW/p-CuInSe2(CIS) material combinations were preferred for the construction of p-n hetero-junction solar cells. Vertically well-aligned Si NWs were synthesized over the surface of n-type silicon wafer by using electroless etching technique. The synthesized Si-NWs embedded into a sputter deposited mono-phase chalcopyrite thin film (CIS) for the realization of nanowire array embedded in thin film type inorganic solar cell, which exhibited a 1.51% power conversion efficiency. In addition to Si nanowires, high aspect ratio vertically well- oriented p- silicon micropillars (MPs) were also synthesized using deep reactive ion Etching (DRIE) process with the BOSCH recipe of cyclical passivation and etching. Three-dimensional (3D) p-Si-MPs/n-ZnO-NWs heterostructures were constructed from hydrothermally grown dense arrays of ZnO nanowires onto these p-type silicon micropillars. The device structures were tested for both the field ionization gas sensor and photovoltaic applications, which showed very promising results. As a final part of this study, TiO2 nanorods (NRs) were grown on FTO glass substrates by using hydrothermal technique, which is sequentially coated with CdTe thin film (sputtering) and subjected to CdCl2 chemical solution treatment to fabricate a core-shell model solar cell with a power conversion efficiency over 0.4% power conversion efficiency.