ATMOSPHERIC-PRESSURE MOCVD DRY PROCESS FOR CDTE PV DEVICES AND ITS PRODUCTION SCALABILITY

摘要

Although the photovoltaic market is currently dominated by crystalline silicon, recent intensive international research has been focusing on the development of amorphous and polycrystalline thin film solar cells, based on a-Si:H, CdTe and CI(G)S, offering more scope for production cost reduction. The demand for PV solar modules has been growing by more than 30%/year and this trend is set to continue for the foreseeable future. Despite challenges faced using metal-organic chemical vapour deposition (MOCVD) for device structures onto polycrystalline or amorphous substrates, consistent cell efficiencies over 10% (AM1.5) for contact areas of 0.25 cm~2 using thin film CdTe have been achieved. Generally, CdTe is deposited both commercially and in laboratories using physical evaporation techniques such as close space sublimation (CSS) or other elemental vapour transport. While these processes have fast throughput they lack flexibility in control of dopants when compared to MOCVD. This paper describes recent results using a research scale horizontal MOCVD reactor for depositing the photovoltaic structure in a sinlge run from the Cd(Zn)S deposition through to the cadmium chloride (CdCl_2) treatment achieving repeatable and uniform device performance using a dry process. The potential for production scalability of such an atmospheric-pressure and dry MOCVD process is discussed.