Optical properties of thin film solar cell structures on imprinted microstructures
Translated title
Optiske egenskaber af tyndfilmssolceller på imprintede mikrostrukturer
Author
Whelan, Patrick Rebsdorf
Term
4. term
Education
Publication year
2013
Submitted on
2013-06-07
Pages
98
Abstract
Tyndfilms-solceller baseret på amorft silicium er meget tynde og skal derfor fange mest muligt af det indkomne lys. Antirefleksbelægninger kan hjælpe, men mikrostrukturering af overfladen virker over et bredere bølgelængdeområde. I dette projekt blev der fremstillet mikrostrukturerede PMMA-substrater (akrylplast) ved mikroprægning, en stempel-lignende proces. PMMA gør de tynde strukturer mere robuste og lettere at håndtere, og processen vurderes egnet til opskalering. Der blev brugt fem forskellige mastere: fire fremstillet ved anodisering af aluminium og én ved anisotrop ætsning i krystallinsk silicium. På de prægede overflader blev der afsat lag af indiumtinoxid (ITO, en gennemsigtig leder), amorft silicium (a‑Si) og aluminium for at efterligne en solcelleopbygning. Refleksion og transmission blev målt, og overfladerne blev kortlagt med AFM og SEM for at bygge modeller, som derefter blev brugt til optiske simuleringer i Lumerical FDTD Solutions. Målingerne viste, at refleksionen af AM1.5-solspektret (en standard for sollys ved jordoverfladen) kunne reduceres til 13,1% for prægede prøver med 300 nm a‑Si og Al sammenlignet med 46,7% for en plan reference med samme lag. Med en antirefleks-ITO-belægning faldt refleksionen yderligere til omkring 9%. Resultaterne peger på, at mikrostrukturering af PMMA via mikroprægning er en lovende, skalerbar måde at reducere refleksionstab i a‑Si-tyndfilmsstrukturer.
Thin-film solar cells made with amorphous silicon are very thin and therefore need to trap as much incoming light as possible. Antireflective coatings can help, but microtexturing the surface works across a broader range of wavelengths. In this project, microtextured PMMA substrates (an acrylic plastic) were produced by micro-imprinting, a stamp-like process. PMMA adds mechanical strength and easier handling to thin-film structures, and the process appears suitable for larger-scale production. Five different masters were used: four made by anodizing aluminum and one by anisotropic etching in crystalline silicon. Layers of indium tin oxide (ITO, a transparent conductor), amorphous silicon (a‑Si), and aluminum were deposited on the imprinted surfaces to mimic a solar cell stack. Reflection and transmission were measured, and the surfaces were mapped with AFM and SEM to build models, which were then used for optical simulations in Lumerical FDTD Solutions. Measurements showed that reflection of the AM1.5 solar spectrum (a standard for sunlight at Earth’s surface) could be reduced to 13.1% for textured samples with 300 nm a‑Si and Al, compared with 46.7% for a flat reference with the same layers. Adding an antireflective ITO layer lowered reflection further to about 9%. These results indicate that microtexturing PMMA via micro‑imprinting is a promising, scalable route to reducing reflection losses in a‑Si thin‑film structures.
[This abstract was generated with the help of AI]
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