Hue tunable, high color saturation and high-efficiency graphene/silicon heterojunction solar cells with MgF2/ZnS double anti-reflection layer

Graphene/silicon (Gr/Si) heterojunctions with simple manufacturing process, high stability and excellent device performance have great potential in photovoltaic (PV) applications. In comparison to conventional PV panels with monotone colors, multi-color PV panels could be integrated in modern building facades and thus largely expand their application ranges. In this work, multi-color Gr/Si heterojunction PV devices were fabricated, for the first time, by taking advantage of the combination of ultra-thin highly transparent graphene and MgF2/ZnS anti-reflection coating. The double-layer film coating enabled the multi-color Gr/Si PV devices with both high color saturation and low optical loss. The PV devices exhibited respectable power conversion efficiency (PCE) in the range of 10.7-13.2%, depending on the color of the devices. In addition, PCE of the device with optimized anti-reflection coating reached as high as 14.6%, which is among the highest for the Gr/Si heterojunction solar cells. By varying the film thickness at different positions, a colored Gr/Si solar cell with visible pattern was made on a 2-in. Si wafer. Our work demonstrates the great potential of multi-colored Gr/Si solar cells for new-generation distributed solar energy systems with designable features.