Improvement of electron diffusion lengths in polycrystalline silicon wafers by aluminium
In order to improve the electron diffusion lei wafers, an aluminium layer was deposited on the back sul 2 h. It was found that Ln is increased, provided the initi; density of dislocations is larger than 5 x 104 cm-2. Backsig to explain the results and it is assumed that dissolved c
3D‐resolved determination of minority‐carrier lifetime in planar silicon solar cells by photocurrent decay
In modern production schemes for Si solar cells, defect passivation and impurity gettering are often used to improve material quality and thereby cell efficiency. These processes generally alter the spatial uniformity of minority‐carrier transport parameters over the wafer and may result in minority‐carrier lifetime and diffusion length variations both lateral and in depth. In polycrystalline Si these spatial dependences are already present due to the nature of the material. We present an extension of the photocurrent decay method to determine the diffusion length in a three‐dimensionally resolved fashion. From a single photocurrent decay curve the back‐surface recombination velocity, the average minority‐carrier diffusion length, and an asymmetry factor which qualitatively describes the depth dependence of the diffusion length are determined. This is done using the three observables: quantum efficiency, fundamental decay time, and intercept of the extrapolated decay curve with the time‐zero axis. Lateral...
The importance of the excitation volume in determination of surface recombination velocity
A Simple approach for evaluating the electron-beam induced current (EBIC) response of a grain boundary in polycrystalline silicon demonstrates that the response is composed of two different responses. At distances greater than two excitation-volume radii from the grain boundary, the response yields an effective surface recombination velocity within about ten percent of that obtained by fitting the data to the theoretical response for a point-source excitation. However, at distance less than two excitation-volume radii, the grain-boundary response is demonstrated to be the response to a skewed Gaussian excitation. This exemplifies the limitations of spacial resolution of an electron probe and the importance of quantitative measurements in determining the effective surface recombination velocity of internal and external surfaces of semiconducting regions.