Optimization of the Asymmetric Intermediate Reflector Morphology for High Stabilized Efficiency Thin n-i-p Micromorph Solar Cells
This paper focuses on our latest progress in n-i-p thinmicromorph solar-cell fabrication using textured back reflectors and asymmetric intermediate reflectors, both deposited by lowpressure chemical vapor deposition of zinc oxide.We then present microcrystalline bottom cells with high crystallinity, which yield excellent long wavelength response for relatively thin absorber thickness. In a 1.5-μm-thick μc-Si:H single-junction n-i-p solar cell, we thus obtain a short-circuit current density of 25.9 mA·cm−2 , resulting in an initial cell efficiency of 9.1%. Subsequently, the roughness of the intermediate reflector layer is adapted for the growth of high-performance amorphous silicon (a-Si:H) top cells. Combining bottom cells with high current, an optimal intermediate reflector morphology and a 0.22-μm-thick a-Si:H top cell, we reach high initial open-circuit voltages of 1.45 V, and we obtain a stabilized cell with an efficiency of 11.1%, which is our best stable efficiency for n-i-p solar cells.