High Efficiency Multijunction III-V Solar Cells through Low-Cost Processing Methods

Reducing the cost of device processing, which includes all the steps necessary to make a working solar cell from epitaxial layers, is important for both the continued dominance of III-V solar cells in space applications and the expansion of their use into terrestrial applications. In this work, we present 3-junction III-V solar cells processed entirely without photolithography or electron-beam metal deposition - the two main drivers of III-V device processing. In this work, we use screen printing to metallize the front grid of the solar cell with a silver/copper nanoparticle ink; spray coating to metallize the back of the solar with a reactive silver ink; and femtosecond laser ablation and cleaving to mesa-isolate the solar cells. While challenges with front grid resolution and contact etching resulted in large short circuit current losses that limited the efficiency of the solar cells to 15.8%, the low-cost-processed solar cells had a promising open circuit voltage of 2.64 V and a fill factor of 86.8%. Current work focuses on addressing the challenges related to the front grid of the solar cell and the implementation of light management strategies to increase the short circuit current density to enable high efficiency devices.