Irrespective of technology, increasing solar cell power conversion efficiency plays a critical role in reducing the cost of PV electricity. Higher-efficiency modules, resulting from higher-efficiency cells, reduce the cost of installation, or balance of system (BoS) costs. This has important ramifications for equipment suppliers.
In an industry dominated by crystalline silicon (c-Si), many of those manufacturers with access to deep financial resources and strong commercial track records are investing in upgrading lines to produce higher-efficiency modules, as opposed to capacity expansion. Tools and processes that can increase power conversion efficiency without jeopardizing existing industrial production capacity are favored.
A new solution is arriving in the form of low-temperature surface passivation by atomic layer deposition (ALD) for c-Si cells. The technology is predominantly used in research labs and for batch processing in the chip industry, but it has potential for several applications in the PV manufacturing industry, including transparent conductive oxide coatings, passivation for c-Si solar cells and buffer layers for thin film CIGS cells. Bram Hoex from Solar Energy Research Institute of Singapore discusses two different examples of near-commercial ALD tools for growing ultra-thin (1-30 nm) aluminium oxide (Al2O3) films for passivation of silicon solar cells.
Of the thin film technologies, amorphous silicon’s (a-Si) potential lies in increasing efficiencies of silicon-heterojunction (Si-HJ) cells to achieve module conversion efficiencies of 20 percent. While plasma-enhanced chemical vapor deposition (PECVD) deployed in the flat-panel display industry has been used in silicon thin film (Si-TF) module manufacturing, focus is turning to development of high-volume production-ready PEVCD systems for making Si-HJ cells. Kun Ho Ahn from Roth & Rau AG provides a comprehensive overview of PECVD for silicon thin film PV production.