High-efficiency heterogeneous multi-junction solar cells fabricated by smart stack technology

Abstract

We have proposed a novel semiconductor bonding technology called smart stack technology for mechanically stacked multi-junction solar cells. This technology utilizes Pd nanoparticle alignment to interconnect the top and bottom cells with low bonding resistances and minimal optical absorption losses. Pd nanoparticle alignment can be formed by a self-assembled phenomenon using a low-cost spin coating method, which is very attractive for interconnecting different kinds of solar cells. We demonstrate III-V 4-junction, InGaP/GaAs//CIGS and InGaP/GaAs//Si 3-junction solar cells. We also describe the thermal reliability test and the stacking mechanisms of smart stack devices. Our method is very useful for realizing the next-generation of low-cost and high efficiency multi-junction solar cells with various heterogeneous cell combinations.