Performance enhancement of III-V multi-junction solar cells using indium-tin-oxide electrodes

InGaP/GaAs dual-junction solar cells were prepared on p-type GaAs substrates by metalorganic chemical vapor deposition. Three types of front-side electrodes, which included AuGe/Au metal-finger, ITO-finger, and ITO-overcoated, were individually fabricated on the devices and denoted as samples A, B, and C, respectively. The thickness of ITO film is 200 nm, and its transmittance can reach 99% in the visible region. Based on the current density-voltage (J-V) measurement, the short-circuit current density (Jsc) of samples A, B, and C are 8.13, 9.35, and 10.90 mA/cm2, while the conversion efficiencies of these three samples are evaluated to be 15.45%, 18.14%, and 20.24%, respectively. This reveals that sample C possesses 31.0% enhancement in the conversion efficiency compared to that of sample A. Additionally, the series resistances (Rs) of samples A, B, and C are 21.43, 22.94, and 6.71 Ω-cm2, respectively. The lowest Rs occurred in sample C can be attributed to the elimination of the lateral resistance between electrodes because this device was fabricated with the ITO-overcoated front-side electrode. In sample C, since the ITO front-side electrode can cover overall surface of the device, all regions on the sample surface can extract the electrons, leading to the highest Jsc.