Semi-transparent photovoltaic devices for smart window applications

Photovoltaic devices integrated into smart windows can provide power necessary to tune the transparency of the windows for energy savings and environmental control. Both wide-bandgap polymer and oxide thin-films can provide visibility necessary through windows as well as voltage to drive the window to vary its transparency. Mini-modules including polymer bulk heterojunction solar cells have been fabricated and the open-circuit voltage up to 7.7 V was obtained from a 6cm × 6cm-size module which contains two banks of the cells connected in parallel, and each bank has 14 cells connected in series. The rectifying heterojunctions of Cu₂O/i-ZnO/AZO were also successfully demonstrated. The presence of i-ZnO is critical to reduce the significant tunneling current caused by considerable band offset and the inherent lattice mismatch at the junction interface.