ITO-free carrier selective contact for crystalline Si solar cells

Abstract

Carrier selective contacts (CSCs) have been proposed to replace the conventional p-n junction because CSCs yield selective hole and electron collections through the negative- and positive-polarity contacts, respectively. For CSCs solar cells, indium tin oxide (ITO) is essential in order to collect the carriers through CSCs because of their relatively low conductivity. However, ITO film formed by sputter deposition leads to serious performance degradation of the CSCs solar cells due to parasitic absorption of ITO and plasma damage during sputtering. In this work, we designed ITO-free transparent metal electrode that can effectively collect carriers separated from the interface between molybdenum oxide (MoOx, hole contact) and c-Si. Although inversion layer in MoOx/c-Si interface has high sheet resistance, we demonstrated that the electrical loss can be minimized in our electrode design. Our micro-scale metal electrode significantly minimizes the optical losses compared to the ITO electrode. In addition, the metal electrode formed by the thermal evaporation prevents sputtering damage, leading to no electrical degradation at the MoOx/Si interface. With this optimized metal electrode, we could obtain the remarkable PCE enhancement of the MoOx/c-Si solar cell achieving a PCE of up to 16% higher than that with the ITO electrode. Thus, the use of our designed metal contact to construct an ideal front electrode presents a unique opportunity to develop highly efficient c-Si solar cells with CSCs.