Light-induced pulsed electroplating to reinforce front metal contacts of solar cells, varies potential, irradiation and current density periodically

摘要

In an electroplating apparatus for the solar cells, one or more of the following are varied: potential difference between electrodes and contacts, irradiation of the solar cells and current density. The relevant potential differences are: delta U RHbetween the first metal contact (R) and the auxiliary electrode (H); delta U RVbetween the first metal contact (R) and the second contact (V) and delta U VHbetween the second metal contact (V) and the auxiliary electrode (H). The applied variation accords with a pre-defined voltage/time characteristic and/or corresponding current density variation. The first metal contact (R) is part of the rear solar cell contact and/or a contact on its p-doped side. In addition or alternatively the second metal contact (V) is part of a front contact, an electrical contact on the side facing the light irradiation and/or a contact on the n-doped side. The voltage, current-density or light irradiation is periodic in time. It follows a pulse sequence. Several pulse sequences, including intervals with no variation, are applied. A triangular-, square- or sine waveform is used. Second-, third- or higher degree polynomial waveforms are used. The waveform is exponential. Potential difference variations are produced by appropriately-connected function generator(s) which vary the relevant potential differences between contacts and electrodes. Irradiation of the solar cells is varied over time by a source connected to a frequency generator varying the voltage supplied. As an alternative the cell may be exposed to continuous light, which is interrupted by a mechanical chopper operating periodically. delta U RHis varied in accordance with the predetermined characteristic. In one variant method, delta U RV, delta U VH, and/or the corresponding current density are not varied. Further details of applied voltage time variations between electrodes are described, in accordance with the foregoing principles. An independent claim IS INCLUDED FOR corresponding apparatus.