Purity matters : enhancing carrier transport properties in tin sulfide for photovoltaic applications by reducing impurity content

Abstract

Tin sulfide (SnS), a potential p-type absorber material for photovoltaic applications, is hampered by poor carrier-transport properties, particularly minority-carrier lifetime. This study investigates the role of intrinsic and extrinsic crystallographic point defects on the electronic transport properties of SnS. High-purity SnS is grown via sulfurization of tin films, and compared with baseline material made from feedstock with two orders of magnitude higher impurity content. Minority-carrier lifetime, morphology, and impurity content are analyzed in both materials. It is shown that improving feedstock purity by two orders of magnitude results in an improvement to minority-carrier lifetime from under 100 ps to over 2 ns. Simulations suggest that this increase in minority-carrier lifetime could lead to device efficiency improvements.