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 λ/d value and used as anti-reflection layer in heterojunction solar cells. For film deposition in the T_s range 150 °C < T_s ≤ 250 °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 λ/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/cm², FF = 0.71, η = 16.3% for T_s = 200 °C. The decrease in performance beyond the T_s of 200 °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.