APPLICATION OF AZO BUFFER LAYER ON COMMERCIAL PET/ITO SUBSTRATES TO IMPROVE THE MECHANICAL STABILITY OF FLEXIBLE A-SI:H SOLAR CELLS

摘要

Low-cost flexible substrates usually limit the a-Si:H deposition temperature to values under 150°C.Hydrogen dilution allows for the improvement of the poor optoelectronic properties obtained at such temperatures,but a higher intrinsic stress is originated in the silicon network. This effect can lead to the development of solar cellsthat are mechanically unstable. In this case, cracked or even completely peeled-off zones could be observed on the pi-n a-Si:H deposit. In the present work, this problem was faced for the particular case of low cost PET/In_2O_3:Sn (ITO)commercial substrates. Since the chemical, morphological, and structural surface properties affect the a-Si:Hnucleation, they could also influence its adherence. Starting from this idea, a solution was proposed based on theinclusion of a thin ZnO:Al (AZO) buffer layer. A noticeable improvement on the a-Si:H adherence was obtained. Inorder to test the mechanical stability limit, a series of devices was prepared increasing the hydrogen dilution ratioused during absorber growth. Solar cells with an excellent intrinsic layer material were prepared, showing a carriermobility-lifetime product (μτ) greater than 1×10~(-7) cm~2/V. The illumination J-V characterisation of these p-i-n devicesallowed of the simultaneously analysis of the influence of the as-deposited defect density on the device performance.