AVS 56th International Symposium & Exhibition
    Electronic Materials and Processing Tuesday Sessions
       Session EM-TuP

Paper EM-TuP8
Life-time Improvement of CdTe/CdS Solar Cells by Application of TiN Diffusion Barrier to Cu2Te Back Contacts

Tuesday, November 10, 2009, 6:00 pm, Room Hall 3

Session: Electronic Materials and Processing Poster Session
Presenter: C. Lim, Chosun University, Korea
Authors: C. Lim, Chosun University, Korea
J. Park, Chosun University, Korea
S. Ryu, Chosun University, Korea
N. Kim, Chonnam National University, Korea
W Lee, Chosun University, Korea
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CdTe is one of the most convincing materials for thin-film solar cells shaped as the CdTe/CdS heterojunction structure. The formation of back contact is the most important and immediate problem to be solved with the low-resistance and excellent stability because the formation of an ideal ohmic contact to CdTe is very difficult with the most metals. Copper (Cu) compounds or copper-doped materials were generally employed for the back contact including ZnTe:Cu, CuxTe, CuxS, and Cu-doped graphite due to its high electrical conductivity, and similar electron affinity to CdTe. However, copper is easily and rapidly diffused to CdTe material; the life-time of CdTe/CdS solar cells is remarkably reduced because the diffused impurity of copper play roles of recombination center and shunt pathway. Therefore, the investigations for an improvement of life-time were widely performed on the formation of the alternative materials without copper or the heat-treatment of copper-containing materials. In this study, a diffusion barrier layer of TiN for an anti-diffusion of copper was employed with the Cu2Te back contacts. TiN is well known as the diffusion barrier because of its good thermal/chemical stability, and low contact-resistance. The relation between the thickness of TiN layer and the diffusion of copper was analyzed by AES depth profile. The energy conversion efficiency and life-time at the optimized thickness was compared and analyzed to the specimen without the passivation layer. The improved life-time of CdTe/CdS solar cells with the good energy conversion efficiency was successfully obtained by the application of the optimized thickness of TiN diffusion barrier.