Current-limiting behavior in multijunction solar cells
Click to view
Measured gain factor as function of for the tandem cell (semilog plots). (a) In the solar concentrator, under uniform and localized irradiation. Averaged irradiance denotes the ratio of the spectrum-adjusted to the cell’s photoactive area (vide supra). The corresponding model calculation described in the text (for uniform cell irradiation) is also shown for both the tandem cell and its individual subcells. The error bars for the calculated curves stem from the experimental uncertainty in the external quantum efficiency input data. (b) Uniform cell irradiation from two laser diodes was adjusted to produce varying degrees of current mismatch (curve labels) at which the tandem cell’s gain factor relative to current matching, , could be determined. .
Click to view
Illustration for summing voltages in serially connected bottom subcell 1 and upper subcell 2, where the curve of current-limiting subcell 1 is noticeably nonhorizontal near . (a) Simplistic summing of voltages, . (b) Determining : the modeled curves of the individual subcells and the tandem are plotted at 3 and 10 suns (for an AM1.5D solar spectrum). For 3 suns, at , subcell 1 is under reverse bias and subcell 2 experiences a forward bias of equal magnitude . is then not limited by subcell 1. At 10 suns (and greater), the required compensating forward bias of subcell 2 is beyond its curve. Consequently, decreases to .
Article metrics loading...
Full text loading...