Liquid Silicon 2.0 - Liquid phase deposition of thin functional silicon layers as enabler for cost-effective high efficiency solar cells

Key-important to all high efficiency solar cell concepts is the targeted deposition of highly doped layers or structures of multi-crystalline silicon (mc-Si). Typically, these layers are generated by vacuum based deposition techniques e.g. CVD (chemical vapour deposition). In many cases necessary subsequent patterning steps result in laborious, multi-step procedures with a high demand of consumable materials and cell manufacturing lines featuring a multitude of costly tools. Liquid phase deposition (LPD) and processing of mc-Si layers starting from hydrogenated polysilanes is an appealing and cost efficient alternative. Precursors currently used in this context such as Si5H10 (CPS), Si6H12 (CHS) or Si5H12 (NPS), however, suffer from the lack of proper synthetic approaches suitable for their preparation on a larger scale, their unsuitable volatility and their undesirable pyrophoric character on contact with air. Primary goal of this project, thus, is the development of commercially viable synthetic pathways suitable for the large scale production of alternative perhydridopolysilane precursor materials ("Liquid Silicon 2.0") for liquid phase silicon deposition with superior characteristics on the basis of a recently elaborated technology concept. Furthermore, mc-Si layers shall be deposited from the resulting target materials, characterized with respect to their potential for PV applications and finally tested in prototype low-cost and high-efficiency solar cells. Within the Austrian workshare of the project experimental procedures developed for the synthesis of "Liquid Silicon 2.0" materials in the course of previous studies shall be adapted and optimized to increase the commercial competitiveness of the process. The primary objective in this context, thus, is the synthesis of the target materials in higher product yields and purity with decreased production costs by less consumables, less waste and fewer synthetic steps compared to the state of the art. The elaborated methods shall be suitable for the synthesis of the target compounds on a >100g scale to experimentally proof the applied concept and to validate the technology in laboratory. Successful realization of the whole project will make highly innovative LPD processed solar cells with high efficiency available on a broad scale to competitive costs which substantially contributes to the objectives of the SOLAR-ERA.NET Initiative.