SURFACE AND LIFETIME STUDIES FOR UNINTENDED DEPOSITION OF NI/CU ON SOLAR CELLS DURING CONTACT PLATING

摘要

Electroplated Ni-Cu based front contacts for c-Si are deposited on patterned ARC and during theprocess unwanted deposition on unpatterned areas can occur which may lead to shading and possible shuntformation. In this work, study of unintended plating on ARC is carried out by surface deposition analysis and carrierlife time studies wherein the front side of solar cells are exposed to electroless Ni bath and electroplating Cubath. It has been observed that for exposure to Ni bath without any pre-treatment, deposition of miscellaneous ionspresent in bath occurs on the ARC which have a shading effect, but tend to recover after annealing. For samples pretreatedwith 1% HF and PdCl2 based solution before Ni plating, Ni deposition was observed with change inreflectance and passivation properties of the ARC. From QSSPC life time studies under UV illumination it wasobserved that decrease in lifetime increased from 20% to 58.5% as the bath temperature increased from 70°C to90°C. A substantial decrease of 22mV in implied Voc resulted after exposure to Ni bath at temperature of 90°C.Dispersed copper deposits were observed for exposure to Cu bath which did not adversely impact the solar cellproperties.