کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
78322 | 49328 | 2013 | 7 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: On the bandgap of hydrogenated nanocrystalline silicon intrinsic materials used in thin film silicon solar cells On the bandgap of hydrogenated nanocrystalline silicon intrinsic materials used in thin film silicon solar cells](/preview/png/78322.png)
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coefficient (α) does not yield a linear relation on the Tauc plot, indicating that the concept of the Tauc bandgap is no longer valid.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=104 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 (Voc) of nc-Si:H solar cells with different Voc 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.
► The Tauc bandgap cannot be defined in hydrogenated nanocrystalline silicon (nc-Si:H) materials.
► The mobility bandgap of nc-Si:H materials can be obtained by the temperature dependence of diode characteristics and temperature dependence of open circuit voltage of nc-Si:H solar cells.
► The mobility bandgap of nc-Si:H materials is similar to the bandgap of crystal silicon and does not depend on the crystallinity.
Journal: Solar Energy Materials and Solar Cells - Volume 111, April 2013, Pages 90–96