“Solar tree”: Exploring new form factors of organic solar cells

Organic solar cells have great potential as a clean and renewable solar energy conversion system, due to their low cost materials, ease of production, and lack of harmful emissions. The rapid improvement in organic solar cell performance in recent years has triggered significant interests in developing organic solar cells for commercial applications. Harnessing the unique set of characteristics of organic solar cells, here we demonstrate a new form factor for organic solar cells, a “solar tree” or an electricity-generating artificial tree with organic solar cells as leaves. We first fabricated polymer:fullerene based organic solar cells on flexible plastic substrates that show similar performance to devices on rigid glass substrates using the inverted device structure. Large-area flexible devices were fabricated and cut into palm leaf shapes with an active device area of 6.5 cm2 using a steel rule die. 12 leaf-shaped organic solar cells were then assembled to form a prototype “solar palm tree”. Two different wiring configurations among the devices provided different power delivery modes: a low-voltage, high-current “fan mode” and a high voltage, low-current “LED mode”.