Photovoltaic technology is emerging as an essential technology to solve climate change, which is the biggest problem facing humanity at present. Competition to secure energy resources around the world is intensifying, including increasing uncertainty in the energy market and unstable supply and demand. Therefore, the development of photovoltaic technology must be indispensable to solve energy problems. It is crucial to achieve high efficiency through research and development of source material and achieve low pricesthrough mass production from two viewpoints of the core technology of sun light. Thin-film silicon solar cell, which is a low-efficiency, low-efficiency thin-film silicon solar cell, is being actively pursued. However, research on hetero-junction solar cells is underway to overcome efficiency. In this paper, we have studied a single junction solar cell with a multi-surface structure for high-efficiency solar cell applications. Primarily, we have studied to improve the optical trapping structure, shape mechanism, and optical characteristics through various surface shape changes of glass substrates. Due to the depletion of the indium material, ZnO thin film was used as a transparent conductive oxide film, which can replace ITO and sputtered. In order to realize the multi-surface structure, firstly, the efficiency improvement of the ZnO:Al thin films deposited on the SnO2:F (FTO) substrate investigated. Based on optimized thin-film conditions, ZnO:Al thin films were deposited on various light trapping glass structures to form multiple surface structures. For the multi-surface structure, etching of ZnO:Al thin film required. When the surface treatment is performed using HF 1% solution for a short time, the crater of the nanostructure is uniformly formed and the multi-surface shape is studied. By optimizing the multi-surface structure as described above, the haze ratio can be improved in the long-wavelength region, which can contribute to the improvement of solar cell efficiency. When the solar cell fabricated using optimized multi-surface, the efficiency was improved to 10.8% (Jsc: 17 mA/cm2, Voc: 900 mV, and FF: 70.1%) with the short circuit current density. We also achieved the design of the tandem cell with a high aspect ratio structure (1.72) (JSC: 15.306 mA/cm2, VOC: 1.405 V, and FF: 71.5%) compared to the low aspect ratio (1.18). For the plasma treatment on the film, the work function was decreased from 5.13 eV to 4.17 eV when increasing the power. This may form a tiny oxide layer at the interface to enhance VOC, but not JSC. We concluded that the decrease of the work function in the ITO film resulted in an increased VOC, generated by the surface heating during the Ar ion bombardment, which activates the out-diffusion of oxygen atoms from inside the ITO thin film. It is possible to optically couple a separately textured glass surface at the front surface of a solar cell and thereby improve light trapping in the device. The advantage of such a scheme is that the FF and Voc of the device do not degrade due to the texture-induced surface defects as the solar cell and surface texturing are done separately. We achieved the efficiency of 22.41% with an index matching solution together with a textured honeycomb glass. Better light trapping is essential for improving device performance. Here, the fabricating solar cell of a thin wafer requires for the high efficiency in boosting of VOC. However, JSC is decreased as decreasing the thickness of wafer. Therefore, we also studied for improving the device performance using a thin wafer. Surface modifications of the Si wafer for the front sided texturing and rear side polishing, which can be obtained the improving the light trapping. Thus, we achieved an efficiency of 23.52 % compared to an efficiency of 23.08% for the reference sample by computer modeling. Both the front side textured surface and rear sided polishing surfaces are helpful for better light trapping within the silicon despite 110 μm-thick. We further investigated n-type wide bandgap material for improving the device performance through the theoretical calculation using the AFORS-HET simulation. We achieved a high efficiency of 25.35 % with a μc-SiO:H film under an electron affinity of 4.1 eV as well as a high doping density of 1019 cm-3. Our investigation indicates that a suitable wide bandgap n-type FSF layer can significantly improve the current density of the cell, and hence the efficiency of the device can improve significantly.