Fabrication and optimization of Al-doped zinc oxide layer for application in radial p-n junction silicon solar cells

The influence of thickness of optimized Al-doped zinc oxide (AZO) front contact layer on an efficiency of a radial p-n junction silicon (Si) solar cell has been studied. Vertically aligned Si wire arrays for the radial p-n junction solar device were fabricated by metal catalytic etching and p-n junction was prepared by spin-on-dopant (SOD) diffusion method. AZO thin films as a top contact layer were conformally deposited on the radial p-n junction Si solar cell by atomic layer deposition (ALD) technique. To determine the best conversion efficiency, the thickness of AZO thin film varied from 15 nm to 80nm. Both short circuit current (Jsc) and power conversion efficiency (η) of the cell increased as the thickness of AZO film is changed from 15nm to 48nm, but decreased at the AZO thicknesses exceeding 48nm. The conversion efficiency of the best sample is 5.6% and Jsc of 22.2mA/cm2, when the thickness of AZO front contact is 48nm. It is considered that the optimized AZO contact layer plays a role of increasing photocurrent by lowering contact resistance and surface recombination centers.