Abstract
AbstractIn this thesis, we report a study of ZnO thin film deposition method cooperating with Industrial Technology Research Institute (ITRI). Our target is trying to find the most proper deposition parameter and ZnO thin film optoelectronic properties for so-lar cell applications. In our research, the proper optoelectronic properties could be ap-proached by using the deposition parameters, ZnO:Al2O3 target, power density 2.26 W/cm2, O2/Ar = 0.1 %, deposition pressure 2 mTorr, the target distance 7 mm and pulse frequency 30 kHz. After 1 μm AZO thin film was fabricated, the sheet re-sistance 6~8 Ω/□ and transmittance above 80 % for visible light could be achieved under the above parameters. Then etching 1 μm AZO thin film by 0.5 % HCl for tex-ture, the roughness of AZO thin film surface is easily controlled by etching time which could be satisfied by ITRI for silicon thin film solar cell research.An adjusted color of amorphous silicon thin film solar cells is illustrated by us-ing a multilayer film design. The multilayer film consists of silver (Ag) and gallium doped Zinc oxide (GZO), which serves as an adjusted color reflection (ACR) multi-layer film. The color can be adjusted with wide range from dark blue to blue red col-ors when the GZO thickness increases from 50 to 150 nm. The color adjusted by the ACR multilayer film is in good agreement with the reflectance response of the multi-layer. The influence of the ACR multilayer film on the solar cell performance is dis-cussed.Boron-doped ZnO (BZO) films were deposited by low pressure chemical vapor deposition (LPCVD) on glass substrates with tin-doped indium oxide (ITO) buffer layers varying from 0 to 100 nm in thickness. The effects of ITO thickness on the structural, optical and electrical properties of BZO/ITO stacks were investigated. The sheet resistances of BZO/ITO stacks were decreased with increasing of ITO thickness while haze factors for BZO/ITO stacks were saturated at an ITO thickness of 50 nm. X-ray diffraction spectra indicate that ITO (222) can promote the preferred orientation of BZO films changing from <110> to <100>. The grain size of the BZO films with ITO buffer layers was larger than that of those without ITO buffer layers. The simu-lated short circuit current of the silicon thin film solar cell when using BZO/ITO stacks as the TCO layers can be increased by a factor of 1.06 at an ITO thickness of 100 nm.This paper demonstrates the growth of highly-textured boron-doped ZnO (ZnO:B) film by using low-pressure chemical-vapor-deposition (LPCVD) for effi-cient light harvesting and carrier collection in heterojunction silicon-based (HJS) solar cells. The optical and electrical characteristics have been optimized versus the sub-strate temperature and B2H6 flow rate for tradeoffs among the sheet resistance, free-carrier absorption, and optical transmission of blue/green wavelengths. A HJS solar cell with a 1.6 um thick ZnO:B film achieves a high power conversion efficien-cy of 16.30 % and fill factor of 78.05 %, compared to 15.64 % and 72.17 %, respec-tively, from a counterpart with a conventional 80-nm-thick indium tin oxide layer.Boron doped ZnO (ZnO:B) films were textured simply by changing the deposi-tion temperature used in low pressure chemical vapor deposition (LP-CVD). Surface morphologies of textured ZnO:B films are very sensitive to deposition temperature, which were characterized by using atomic force microscope and scanning electron microscope. The textured ZnO:B films were applied to fabricate amorphous hydro-genated silicon (a-Si:H) thin film solar cells. The a-Si:H thin film was prepared by plasma enhanced chemical vapor deposition (PECVD) operated at 40 MHz. The best device performance of a-Si:H thin film solar cells occurs at 160 oC, which is attribut-ed to the optimization of the surface morphology of ZnO:B. A textured ZnO:B film with a higher root-mean-square (RMS) value can enhance diffusion transmittance and contribute short-circuit current (Jsc). However, critical surface roughness exists, be-yond which long stripe nano-cracks are generated near the surface valleys of ZnO:B. This accompanies with the reduction of Jsc and fill factor (F.F.).