![]() 5 together with the uncertainty interval obtained by the fitting procedure. For this calculation, this is the most reasonable uncertainty since the calibration factor is also determined at this concentration. Uncertainties of transmission measurements were determined through evaluation of the uncertainty of the mean using Student’s t-distribution on ten subsequent measurements for a constant BH concentration of = 8 × 10 14 cm − 3, which is used for the calculation of the calibration factors and their uncertainty. (2) were used as reference points since this is the best way to incorporate the different uncertainties of the single measurements. ![]() The maxima of fitted curves according to Eq. The integrated absorption coefficient (quotient α / ν ~) can be normalized to Δ obtained by resistivity measurements. Due to the scatter of the individual measuring points along the fitting line, an uncertainty of this reference point must be assumed, which affects all other points. (9), the evaluation relies on the last data point as a reference point. The reason for this significant deviation is difficult to find since a possible underlying effect would only occur at the initial measurement and would only affect the absorption by free charge carriers, but not the resistance. First, the evaluation by IR measurements seems to overestimate the initial BH concentration by about 3 × 10 14 cm − 3. There are inconsistencies between the two data sets. 2 in comparison with the values obtained by direct resistance measurements. (9), and the result of this evaluation is depicted in Fig. The fitted Drude absorption in the wavenumber range between 16 cm − 1 was evaluated with Eq. With respect to the reference state α Drude, 0 with hole concentration p 0 (obtained from resistivity measurements) at t = 1300 h. 1,10 Although recent developments have shown that high precision can be achieved with this approach, 8,11 the change in resistivity is unspecific and not necessarily only due to the formation of dopant-hydrogen pairs. An alternative approach is indirect quantification by the tendency of hydrogen to form dopant-hydrogen pairs, thus changing bulk resistivity. Since typical hydrogen concentrations in silicon solar cells are only in the range of 10 14– 10 15 cm − 3, 7–9 direct detection, e.g., by secondary ion mass spectrometry, is extremely difficult and often requires the use of less abundant deuterium. 2–6 To clarify the dependence of the degradation on the hydrogen content, a precise quantification is necessary. ![]() 1 Despite its ability to passivate a multitude of recombination active defect species in silicon solar cells, hydrogen is also involved in the formation of recombination active defects in degradation phenomena, such as Light- and elevated Temperature-Induced Degradation (LeTID). Hydrogen plays an important role in crystalline silicon for its ability to passivate and neutralize defects and impurities. This calibration was performed with the absorption α as well as with the quotient of absorption and wavenumber α / ν ~. The comparison of stretching mode absorption strength and change in resistivity allows for a calibration of specific absorption, yielding a calibration factor A BH. The latter is found to fairly match not only the changing strength in absorption of the stretching mode, but also the change in hole concentration obtained by highly sensitive resistivity measurements. Furthermore, the change in free-carrier absorption (described by Drude’s theory) is used to derive the change in hole concentration concurring with the formation and dissociation of boron–hydrogen pairs. Since the measurements were performed at room temperature, this method allows investigations with little effort and standard laboratory equipment. Infrared absorption spectra, which have been corrected for multiple reflection and free-carrier absorption, show absorption related to the boron–hydrogen stretching mode at ν ~ = 1868 cm − 1 with varying strengths during formation and subsequent dissociation of boron–hydrogen pairs triggered by annealing in the dark at 220 ° C. Hydrogen-rich amorphous silicon nitride was deposited on stripes of boron-doped float-zone silicon (1 Ω cm), which were exposed to a rapid high temperature step to introduce relatively high amounts of hydrogen into the wafer. The method presented here allows for direct boron–hydrogen pair quantification and, therefore, allows inference on total hydrogen content. The ability of hydrogen quantification in crystalline silicon in concentrations as low as 10 14 cm − 3 becomes fairly important in regard to hydrogen-related degradation phenomena in silicon devices generally and solar cells particularly.
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