High‐Performance and Stable Dopant‐Free Silicon Solar Cells with Magnesium Acetylacetonate Electron‐Selective Contacts

One of the challenges in fabricating high‐performance n‐type crystalline silicon (n‐type c‐Si) solar cells is the high‐quality n‐type c‐Si/metal contact. Schottky barriers are commonly found on the n‐type c‐Si/metal contact, which suppresses electron transportation. Herein, novel stacks of magnesium acetylacetonate (Mg(Acac) 2 )/magnesium (Mg)/silver (Ag) to form electron‐selective contacts for n‐type c‐Si solar cells are presented, which enables a dopant‐free process. An ohmic contact on n‐type c‐Si is formed using the Mg(Acac) 2 /Mg/Ag stacks. The transmission spectrum and ultraviolet photoelectron spectroscopy measurements show negligible conduction‐band offset and large valence‐band offset between Mg(Acac) 2 and n‐type c‐Si, which indicates the electron‐transporting and hole‐blocking properties of Mg(Acac) 2 /n‐type c‐Si heterocontacts. Moreover, the contact resistivities ( ρ c ) between the Mg(Acac) 2 /Mg/Ag electron‐selective heterocontacts and n‐type c‐Si substrates are lower than 10 mΩ cm 2 , which demonstrates the good electrode properties of the Mg(Acac) 2 /Mg/Ag stacks. The Mg(Acac) 2 /Mg/Ag electron‐selective stacks are applied on n‐type c‐Si solar cells with partial rear contact, and >20% efficiency is achieved, which is higher than that in a reference cell with only Ag contact. The stability of the n‐type c‐Si solar cell performance equipped with Mg(Acac) 2 /Mg/Ag contacts is verified under ambient conditions. This novel low‐temperature contact technique offers a reliable alternative for high‐performance n‐type c‐Si solar cells.