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As the effects of climate change continue to exacerbate, it is crucial to shift to
renewable energies as our primary energy sources. Benefits go beyond curbing
greenhouse gases emissions and have, for instance, positive impacts on human
lives in terms of health, social stability, and energy security of countries.
The present thesis explores silicon thin film solar cells (TFSC) as one possible
answer to the increasing energy demand, particularly to be applied in the
emerging and fast-growing field of paper-based devices, to power autonomous
optoelectronic biosensors. Such devices tend to be recyclable, flexible,
lightweight, and low-cost. For such applications to become a reality, this thesis
explores optimization methodologies for key fabrication steps of silicon TFSCs
to achieve a sustainable and energy efficient process, with reduced resource
consumption, and compatible with temperature-sensitive paper-based substrates:
Experimental design and statistical analysis were combined to develop a
methodology to explore in a multidimensional fashion the interactions between
fabrication parameters and experimental outputs. This optimization step of the
layer structure of TFSC was performed on glass and lead to a device with a power
conversion efficiency of 5.2%, FF ≈ 66%, JSC = 9 mA·cm-2, and VOC = 0.88 V.
Transparent conductive oxides (TCOs) based on doped zinc oxides materials
(AZO, AZO:H, GZO:H and ZnO:H) were optimized by post-deposition
annealing methods. Results show that these materials, with resistivity < 4 × 10-4
Ω.cm, a high transmittance > 85%, can be cost-effective and sustainable
alternatives to the industrial standard ITO.
The combination of optimization processes led to a first-time report of the
viability of fabricating silicon TFSC on paper-based substrates, by PECVD, with
a power conversion efficiency of ~4.1%, FF ≈ 54%, JSC = 9.05 mA·cm-2, and
VOC = 0.84 V. The power density of an envisioned PV module at the current
technology stage is in line with the power requirements of paper-based
optoelectronic devices under development. Amid the possibilities, silicon TFSC
can power point-of-care tests and contribute to a more responsive care through
immediate diagnosis and subsequent clinical/therapeutic decision-making.
Descrição
Palavras-chave
silicon solar cells paper-based substrates transparent conductive oxides optimization PECVD optoelectronics