Flexible Ultra-Thin Silicon Solar-Cell Implemented with Energy-Down-Shift Via Cd0.5Zn0.5s/ZnS Core/Shell Quantum Dots
We, therefore, developed a flexible ultra-thin silicon solar-cell implemented with energy-down-shift layer via Cd0.5Zn0.5S/ZnS core/shell quantum-dots (QDs). In particular, in order to achieve a low cost solar-cell fabrication, we introduced ultra-thinning process (~30-um in thickness) via KOH etching, back-surface-filed (BSF) formation via thin Al-film evaporation and rapid-thermal annealing (RTA), top electrode patterning via thin film Ag evaporation, and spin-coating of core/shell QDs. In addition, in order to enhance an external quantum efficiency (EQE) at ultra-violet (UV) wavelength region, we implemented energy-down-shift layer by coating Cd0.5Zn0.5S/ZnS core/shell QDs on flexible ultra-thin silicon solar-cells.
It was observed that flexible ultra-thin (~30-um in thickness) silicon solar-cells implemented with energy-down-shift layer showed stable flexible and twistable characteristics as shown in Fig. 1. In addition, Fig. 2 presents the EQE as function of wavelength and current density vs. voltage characteristics. It was confirmed that the Cd0.5Zn0.5S/ZnS core/shell QDs on the flexible ultra-thin solar-cells enhanced the EQE of about 17 %P at the UV light region (300 – 400 nm) as shown in Fig. 2(a). In particular, the QDs enhanced the PCE to 0.77%P by the energy-down-shift effect that enhanced the EQE, which resulting in that the PCE of the ultra-thin silicon solar-cells was about 12.37 %.
In the conference, we will present in detail physical, optical electrical, and flexible properties of flexible ultra-thin silicon solar-cells implemented with energy-down-shift layer. In particular, we will report how their PCE can be sustained after the bending cycles of 5,000.
* This work was financially supported by the Brain Korea 21 Plus Program in 2015.
 DH Lee, JY Kwon, and S Maldonado Nano letters 14(4), 1961-1967(2014)