Thin film solar modules: the low cost, high throughput and versatile alternative to Si wafers

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Abstract
Thin film solar cells (TFSC) have passed adolescence and are ready to make a substantial contribution to the world's electricity generation. They can have advantages over c‐Si solar modules in ease of large area, lower cost manufacturing and in several types of applications. Factors which limit TFSC module performance relative to champion cell performance are discussed along with the importance of increased throughput and yield. The consensus of several studies is that all TFSC can achieve costs below 1 $/W if manufactured at sufficiently large scale >100 MW using parallel lines of cloned equipment with high material utilization and spray‐on encapsulants. There is significant new commercial interest in TFSC from small investors and large corporations, validating the thin film approach. Unique characteristics are discussed which give TFSC an advantage over c‐Si in two specific markets: small rural solar home systems and building integrated photovoltaic installations. TFSC have outperformed c‐Si in annual energy production (kWhrs/kW), have demonstrated outdoor durability comparable to c‐Si and are being used in MW scale installations worldwide. The merits of the thin film approach cannot be judged on the basis of efficiency alone but must also account for module performance and potential for low cost. TFSC advocates should promote their unique virtues compared to c‐Si: lower cost, higher kWhr/kW output, higher battery charging current, attractive visual appearance, flexible substrates, long‐term stability comparable to c‐Si, and multiple pathways for deposition with room for innovation and evolutionary improvement. There is a huge market for TFSC even at today's efficiency if costs can be reduced. A brief window of opportunity exists for TFSC over the next few years due the Si shortage. The demonstrated capabilities and advantages of TFSC must be proclaimed more persistently to funding decision‐makers and customers without minimizing the remaining challenges. Copyright © 2006 John Wiley & Sons, Ltd.