Lithium inserted ZnSnN2 thin films for solar absorber: n to p-type conversion

Abstract

ZnSnN2 is a non-toxic and earth-abundant photoabsorber material for flexible photovoltaic devices because of its excellent optoelectronic behavior. However, theoretical studies show that the alkaline-earth metallic (Li, Na, K, Rb, Cs, and Fr) dopants in ZnSnN2, particularly lithium (Li), display shallow-acceptor behavior and improve the performance of ZnSnN2 semiconductors. Orthorhombic phase structure with (002) preferred orientation was observed for Li-doped films and the lattice parameters agree well with reported standards. Secondary ion mass spectroscopy (SIMS) analysis revealed the incorporation of Li in Li:ZnSnN2 films. XPS, the density of states, and Born effective charge analysis revealed the chemical bonding states of Li-ZnSnN2. In contrast to the pristine n-type ZnSnN2, Li:ZnSnN2 thin films showed conductivity with p-type hole concentrations varying between 1.14 x 1020 -9.47 x 10(19) cm(-3) and the highest mobility of 20.03 cm(2)V(-1)s(-1). Therefore, we obtained p-type conductivity by substituting an organolithium reagent (C4H9Li) on the Zn site, which highlights that Li:ZnSnN2 can be effectively used as the photoanode layer for next-generation thin-film solar cell devices. (C) 2022 Elsevier Ltd. All rights reserved.