Yoon, Ju-Heon Yoon, Kwan-Hee Kim, Won Mok Park, Jong-Keuk Baik, Young-Joon Seong, Tae-Yeon Jeong, Jeung-Hyun 2024-01-20T16:03:17Z 2024-01-20T16:03:17Z 2021-09-05 2011-10-26 0022-3727 https://pubs.kist.re.kr/handle/201004/129875 The thermal stability of Mo thin films is indispensable to Cu(In,Ga)Se-2 (CIGS) solar cells: CIGS films are deposited above 500 degrees C. The thermal stabilities of Mo thin films with dense to porous Mo microstructures, which are varied by controlling the sputtering pressure, are investigated. Interface failures are found to occur in buckling mode in denser Mo films, whereas cracking arises in less dense films. The failure modes are apparently dependent on the sign of the residual stress: the former is due to compressive stress, whereas the latter is due to tensile stress. Interestingly, the softening of soda-lime glass at high temperatures reconfigures the film stresses to be more compressive after annealing, which in turn triggers buckling even in films that are tensile-stressed in the as-deposited states. We conclude that the appropriate processing conditions for thermally stable back contacts cannot be obtained with the simple single layer approach. On the basis of this relationship between microstructure, residual stress and the failure modes, it is shown that improvements in film adhesion can widen the processing window for the preparation of robust back contacts, i.e. with a conventional bilayer approach and substrate roughening. Since the bilayer approach employed more compliant porous structures in the bottom layer, back contacts that are better suited to higher stress and temperature can be produced. Furthermore, substrate roughening might make the back contact more conductive as well as more stable because adhesion can be enhanced without the use of an electrically resistive buffer layer. English IOP PUBLISHING LTD SPUTTERED MOLYBDENUM MECHANICAL-PROPERTIES YOUNGS MODULUS MICROSTRUCTURE FILMS High-temperature stability of molybdenum (Mo) back contacts for CIGS solar cells: a route towards more robust back contacts Article 10.1088/0022-3727/44/42/425302 1 JOURNAL OF PHYSICS D-APPLIED PHYSICS, v.44, no.42 JOURNAL OF PHYSICS D-APPLIED PHYSICS 44 42 scie scopus 000296590300012 2-s2.0-80055087062 Physics, Applied Physics Article SPUTTERED MOLYBDENUM MECHANICAL-PROPERTIES YOUNGS MODULUS MICROSTRUCTURE FILMS Molybdenum back contact CIGS solar cell high-temperature stability