rf-Magnetron sputtered ITO thin films for improved heterojunction solar cell applications

Indium tin oxide (ITO) films of low resistivity, high transmittance and good figure of merit were prepared by radio frequency magnetron sputtering, at different substrate temperatures (T-s) under such a high lambda/d value and used as anti-reflection layer in heterojunction solar cells. For film deposition in the T-s range 150 degrees C < T-s <= 250 degrees C, XRD shows that coexistence of the < 1 0 0 > and < 1 1 1 > textures. The resistivity and Hall mobility of ITO films were improved due to thermally induced crystallization. However, carrier concentration of these ITO films is sensitive to the T-s. We attributed these effects to the Ar+ ions bombardment and differing adatom mobility of the heated atoms on the substrate under such a high lambda/d value. Those ITO films were used to fabricate single-side heterojunction solar cells. As the T-s is increased, the device performance improves and the best photo voltage parameters of the device were found to be V-oc = 640 mV, J(sc) = 36.90 mA/cm(2), FF = 0.71, g = 16.3% for T-s = 200 degrees C. The decrease in performance beyond the T-s of 200 degrees C is attributed to hydrogen effusion to the defect in emitter layer. We noted that the figure of merit value of ITO films was reflected in the performance of devices. (C) 2010 Elsevier B. V. All rights reserved.