On the bandgap of hydrogenated nanocrystalline silicon intrinsic materials used in thin film silicon solar cells
| Autor: | Guozhen Yue, Baojie Yan, Jeffrey Yang, Subhendu Guha |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
Materials science
Silicon Renewable Energy Sustainability and the Environment Band gap business.industry Open-circuit voltage Nanocrystalline silicon chemistry.chemical_element Surfaces Coatings and Films Electronic Optical and Magnetic Materials law.invention Crystallinity chemistry law Tauc plot Solar cell Optoelectronics Absorption (electromagnetic radiation) business |
| Zdroj: | Solar Energy Materials and Solar Cells. 111:90-96 |
| ISSN: | 0927-0248 |
| DOI: | 10.1016/j.solmat.2012.12.038 |
| Popis: | We present optical and electrical measurements of bandgap of hydrogenated nanocrystalline silicon (nc-Si:H). The absorption coefficient ( α ) does not yield a linear relation on the Tauc plot, indicating that the concept of the Tauc bandgap is no longer valid. The energy at the absorption coefficient α =10 4 cm −1 increases with crystallinity, but it does not imply that the optical bandgap increases with crystallinity. Instead, it reflects the characteristics of mixed-phase material, where the crystalline phase has lower absorption than the amorphous phase. Dark current versus voltage measurements of nc-Si:H solar cells as a function of temperature showed that the products of ideality factor and the activation energy of the pre-factor are the same for nc-Si:H solar cells with different crystallinities. A mobility bandgap at 0 K of 1.06 eV was derived from these studies. Finally, the temperature dependence of open circuit voltage ( V oc ) of nc-Si:H solar cells with different V oc values at 25 °C shows the same intersection of 1.04 eV at 0 K. It provides additional evidence that the mobility bandgap is independent of crystallinity and is similar to that of c-Si. The values obtained from both the methods are similar to but smaller than the bandgap of c-Si at 0 K; however, the difference could result from experimental errors. |
| Databáze: | OpenAIRE |
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