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 (rho(c)) between the Mg(Acac)(2)/Mg/Ag electron-selective heterocontacts and n-type c-Si substrates are lower than 10 m omega 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.