Molybdenum (Mo) is commonly used as back contacts for Cu(In,Ga)Se2 (CIGS) thin film solar cells because it has the good electrical properties of an ohmic contact and is an inert, mechanically durable substrate during the absorber film growth. In general, Mo is deposited by dc sputtering onto soda-lime glass substrates. The electrical and the mechanical properties of sputtered refractory metal films are known to vary with the working gas pressure. CIGS thin film growth occurs at temperatures > 500 and at these temperatures, the thermally induced extrinsic stresses in the glass-Mo structure may cause bending or mechanical distortion of substrate. During the formation of CIGS films, Na ions diffuse from the soda-lime glass substrate through the Mo back con-tact into the absorber layer. The diffusion of Na into the absorber film depends on the deposition conditions of the Mo back contact.
Molybdenum films were deposited on soda-lime glass substrates by using DC magnetron sputtering. Their structural and morphological properties and their electrical resistivities were analyzed with respect to the working gas (Ar) pressure. The electrical resistivity of the Mo films monotonically increased as the gas pressure was increased. The films showed a (110) preferred orientation,regardless of the working gas pressure. The surface morphology of the films changed from an elongated grain structure at lower working pressures to a porous nodular shape at higher pressures.The surface roughness of the films increased with the working gas pressure. Secondary ion mass spectrometry data showed that Na diffusion from the soda lime glass substrate through the Mo back contact was high, for the film sputtered at 5m Torr. Cu(InGa) Se2 solar cells fabricated on Mo films sputtered at 5 m Torr showed the best conversion efficiency.
If you have any inquires concerning molybdenum products, please don't hesitate to e-mail us by : sales@chinatungsten.com or info@chinatungsten.com
没有评论:
发表评论