Dopant‐free back contact silicon heterojunction solar cells employing transition metal oxide emitters

Abstract

The present study investigates the electrical properties of transition metal oxide (TMO) emitters in dopant‐free n‐Si back contact solar cells by comparing the properties of solar cells employing three TMOs (WO x , MoO x and V 2 O x ) with varying electrical properties acting as p‐type contacts. The TMOs are found to induce large band bending in n‐Si, which reduces the injection level dependent interfacial recombination speed S eff and contact resistivity ρ c . Among the TMO/n‐Si contacts considered, the V 2 O x /n‐Si contact achieves the lowest S eff of 138 cm/s and ρ c of 0.034 Ω cm 2 , providing the significant advantages over heavily doped a‐Si:H(p)/n‐Si contacts. The best device performance was achieved by the V 2 O x /n‐Si solar cell, demonstrating an efficiency of 16.59% and an open‐circuit voltage of 610 mV relative to solar cells based on MoO x /n‐Si (15.09%, 594 mV) and WO x /n‐Si (12.44%, 539 mV). Furthermore, the present work is the first to employ WO x , V 2 O x and Cs 2 CO 3 in back contact solar cells. The fabrication process employed offers great potential for the mass production of back contact solar cells owing to simple, metal mask patterning with high alignment quality and dopant‐free steps conducted at a lower temperature.