Description
Increasing urban developments increases energy demands which can be partly met by innovative building integrated photovoltaic solutions such as energy efficient photovoltaic windows that are semitransparent and colour neutral for visual amenities. Tandem cells if well designed in solar windows may improve conversion of high- and low- energy photons from the solar spectrum into electrical energy which provides an added advantage of heat control.
This study evaluates the merits of double-junction tandem solar cells for such application in terms of colour neutrality and total energy conversion efficiency considering both electrical and room illumination outputs. This is the first time such metric is applied to double junction solar cells addressing the gap in knowledge in the best conditions that a double-junction tandem solar cell has a higher total energy efficiency than a single-junction cell, and best band gap combinations for colour neutrality when applied in solar windows.
We find that both single- and double- junctions can be colour neutral for a wide range of bandgaps. For single junctions, colour neutrality is possible for bandgap <1.87eV at 50% absorption and this range can be extended as transparency increases. For example, colour neutrality can be achieved for bandgap <1.98eV at 10% absorption. For double junctions, colour neutrality is possible when top cell bandgap <1.95eV for 50% absorption in each sub-cell.
Double junctions with equal absorptions in the top and bottom cells are effective in maximising total energy efficiency. We find that double-junction solar cells are an effective semi-opaque (high absorption) solar window solution when electrical output is a priority over illumination. On the other hand, single junction solar windows produce higher total energy efficiency than single junction solar windows when transparency (low absorption) is favoured.
| I am the presenting author | Yes |
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