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High potential of thin (<1 µm) a‐Si: H/µc‐Si:H tandem solar cells
Author(s) -
Schicho S.,
Hrunski D.,
van Aubel R.,
Gordijn A.
Publication year - 2010
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.929
Subject(s) - tandem , materials science , quantum efficiency , thin film , plasma enhanced chemical vapor deposition , layer (electronics) , optoelectronics , amorphous silicon , open circuit voltage , silicon , analytical chemistry (journal) , nanotechnology , chemistry , composite material , crystalline silicon , voltage , physics , chromatography , quantum mechanics
Silicon based thin tandem solar cells were fabricated by plasma enhanced chemical vapor deposition (PECVD) in a 30 × 30 cm 2 reactor. The layer thicknesses of the amorphous top cells and the microcrystalline bottom cells were significantly reduced compared to standard tandem cells that are optimized for high efficiency (typically with a total absorber layer thickness from 1.5 to 3 µm). The individual absorber layer thicknesses of the top and bottom cells were chosen so that the generated current densities are similar to each other. With such thin cells, having a total absorber layer thickness varying from 0.5 to 1.5 µm, initial efficiencies of 8.6–10.7% were achieved. The effects of thickness variations of both absorber layers on the device properties have been separately investigated. With the help of quantum efficiency ( QE ) measurements, we could demonstrate that by reducing the bottom cell thickness the top cell current density increased which is addressed to back‐reflected light. Due to a very thin a‐Si:H top cell, the thin tandem cells show a much lower degradation rate under continuous illumination at open circuit conditions compared to standard tandem and a‐Si:H single junction cells. We demonstrate that thin tandem cells of around 550 nm show better stabilized efficiencies than a‐Si:H and µc‐Si:H single junction cells of comparable thickness. The results show the high potential of thin a‐Si/µc‐Si tandem cells for cost‐effective photovoltaics. Copyright © 2010 John Wiley & Sons, Ltd.