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8th World Conference on Photovoltaic Energy Conversion; 123-127, Various amorphous silicon (a-Si:H) deposition methods for heterojunction solar cells were investigated regarding their suitability for effective wafer passivation and high solar cell efficiencies. Among them, radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) is the standard approach for low temperature a-Si:H fabrication, while very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) and hot-wire chemical vapor deposition (HW-CVD) are emerging technologies to achieve softer deposition conditions. High effective carrier lifetimes of about 9 ms and high efficiencies of about 22 % for heterojunction solar cells were achieved with all deposition methods. A better passivation with soft VHF-PECVD and HW-CVD could not be verified. However, the latter deposition methods enable higher deposition rates but therefore require elaborate power coupling compared to state-of-the-art RF-PECVD. For reference reasons, a high temperature a-Si:H fabrication process, namely lowpressure chemical vapor deposition (LPCVD), was also applied and the layer properties were compared to the standard low-temperature approaches.

38th European Photovoltaic Solar Energy Conference and Exhibition; 358-362, The catalytic chemical vapor deposition technology (CAT-CVD), also called Hot-Wire CVD (HW- CVD), is a commonly used technique for the production of various thin-film materials in many branches of the thin- film industry. The focus of this work has been placed on the process development of the hydrogenated amorphous silicon thin-film (a-Si:H) deposition used for fabrication of highly efficient heterojunction solar cells with intrinsic thin layer (HIT). The advantages of the HW-CVD technique are high deposition rates and a lack of plasma damage which is a significant feature in the production of the thin-film layers. The main subject of this work is the development of a high-rate dynamic deposition technique, which enables the realization of a process on large area substrates and in roll- to-roll systems.

37th European Photovoltaic Solar Energy Conference and Exhibition; 290-294, The main invention in this work is an application of HW-CVD and PECVD technique in one dynamic deposition system, utilizing the advantages of both methods. The focus here has been placed on the compatibility of both deposition technologies in the production of layer stacks used in the solar cell fabrication. The process parameters were developed in such a way, that different combinations of i-, p- and n- layers using PECVD and HW-CVD were deposited during a single in-line dynamic process run. Electrical parameters of fabricated thin films, as well as the passivation properties of the layer stacks, and characteristics of the HIT solar cells, give a clear picture of the quality of the combined deposition procedure. The latest results clearly show that the passivation layers with high lifetime values (14 ms) can be achieved for both deposition methods. Although, during the fabrication of the solar cells using stacks of HW-CVD i-layer and PECVD n/p-layers a degradation of the open-circuit voltage (Voc) was observed. One possible explanation for these phenomena can be that the ion bombardment during the PECVD process degrades the properties of i-HW-CVD layer. Thus, for better understanding, the electrical and structural properties of different conducting and intrinsic materials and their stacks were analyzed. Finally, complex simulation studies of HW-CVD and PECVD processes were performed to explain the principle differences between these two deposition methods.

36th European Photovoltaic Solar Energy Conference and Exhibition; 533-537, In this study a first direct comparison of three fabrication methods for high-rate fabrication of amorphous silicon (a-Si:H) in the same deposition system will be carried out. High-efficiency heterojunction solar cells with intrinsic thin-layer (HIT) are fabricated with various techniques: radio frequency (RF-), and very high frequency (VHF-) plasma enhanced chemical vapor deposition (PECVD) and hot wire chemical vapor deposition (HW-CVD) [1-4]. In this study the evaluation of process parameters for each technology will be presented. Furthermore, the properties of an in-line deposition system containing a RF-, VHF-PECVD and HW-CVD chamber for static and dynamic fabrication will be discussed. The a-Si:H layers fabricated with varied silane concentrations and deposition rates on polished (100) and textured wafers (111) will be studied. The passivation quality for each process will be evaluated by means of the effective carrier lifetime (eff). Finally, the individual steps taken to develop the a-Si:H passivation process with high carrier lifetimes and high open-circuit voltage (Voc > 720 mV) values for high efficiency solar cells (>22 %) fabricated with PECVD and HW-CVD technology will be presented.