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High-Performance Photovoltaics

In an ideal multijunction cell, the top layer produces most of the total power, so the top layer should be of the highest quality. However, in conventional designs grown from the bottom layer to the top, the structure of the top cell is degraded. NREL's Electronic Materials and Devices Project is developing a novel approach to overcome this problem: growing the multijunction layers upside down. These 'inverted' cells have many advantages and the potential to exceed 0%-efficient concentrator conversion. A world-record 7.9%-efficient concentrator cell has already been demonstrated using this approach. Additional strategies for lower-cost, high-performance concentrator cells being pursued by the EM and D project include growing multijunction cells on silicon substrates.

This MicroDish made by Concentrating Technologies uses Spectrolab solar cells. It is the world's first grid-tied high-concentration CPV system to use the latest high-efficiency cells. The dual-axis tracking modules use small mirrors to focus sunlight on high-efficient multijunction cells. It is supplying electricity to the Arizona Public Service grid.

The High-Performance Photovoltaics Project (HiPerf PV Project) aimed to explore the ultimate performance of PV technologies and to approximately double their sunlight-to-electricity conversion efficiencies during its course. The Project enabled progress of high-efficiency technologies toward commercial-prototype products. Today, concentrating PV (CPV) companies are growing rapidly based on the high cell efficiencies (> 40%) that have been achieved for multiple cell architectures.