Effect of additional HfO2 layer deposition on heterojunction c-Si solar cells

The efficiency of a heterojunction with intrinsic thin-layer (HIT) solar cell with an insulator/ITO structure was discussed in this paper. First, the efficiency was analyzed by OPAL 2 simulations. Second, an insulator/ITO structure was experimentally applied to a HIT solar cell. The OPAL 2 simulations using an insulator/ITO/Si structure and a TCO/ITO/Si structure showed that the generation current density in the Si substrate increased when the insulator or TCO layer had a proper thickness. Experimentally, HfO2, a type of insulator, was deposited on a HIT solar cell with a thickness varying from 3 to 15 nm. The average efficiency of the HIT solar cell improved from 18.21% to 20.75% after HfO2 deposition. The highest efficiency was achieved for the 3-nm-thick HfO2/HIT solar cell structure, which exhibited the best improvement in the current density of approximately 1.5 mA/cm(2). For the external quantum efficiency of the HfO2/HIT solar cell, the total absorption was improved by HfO2 deposition. The results suggest that the HfO2 layer improves the solar cell efficiency of the HIT solar cell by increasing light absorption.