Transparent and conductive multi-functional window layer for thin-emitter Si solar cells

摘要

Optically transparent and electrically conductive multi-functional window layer was applied for Si solar cells. A thin indium-tin-oxide (ITO) has a high optical transparency of 89.1% and was coated on pyramidal-shaped Si to provide significantly suppressed reflection at surface. This ITO-window serves as an electrical conducting layer (55.2 Omega/square) on Si, which relives the high-doping requirement for an emitter layer. We applied the transparent ITO electrical conducting layer for Si solar cells with modulation of thickness of Si emitter. A thin-emitter has benefits to locate a space charge region close to the Si surface to render a shorter transport length of photogenerated carriers, resulting in higher collection efficiency, compared to those of thick-emitter. ITO-windowed thin-emitter provided a relatively high current density value of 34.34 mA/cm(2), which is 32%-enhanced value from 25.92 mA/cm(2) of the thick-emitter. We demonstrate a functional design of transparent conductor-embedding Si solar cells and suggest a route for further improvement.