Large cubic tin sulfide–tin selenide thin film stacks for energy conversion

Abstract Large cubic (CUB) polymorphs of SnS and SnSe were identified in nanocrystals and in thin films during 2015–16. We present how thin films of SnS-CUB and SnSe-CUB can be stacked in different sequences to thickness of 450 nm by chemical deposition. Grazing incidence X-ray diffraction pattern of the films establishes how these stacks of materials with a lattice constant a = 11.59 A for SnS-CUB and 11.96 A for SnSe form, upon heating at 300 °C, composite layers of SnS-CUB + SnS 0.75 Se 0.25 -CUB + SnSe-CUB. The layers so formed have optical band gap of nearly 1.52 eV, intermediate to that of SnSe-CUB and SnS-CUB, of 1.38 and 1.73 eV, respectively. With optical absorption coefficient exceeding 10 5 cm − 1 in the visible region, the stacks would produce light generated current density of 28–31 mA/cm 2 in solar cells for air mass 1.5 global solar radiation. Electrical conductivity of 0.01 Ω − 1 cm − 1 , and Seebeck coefficient of up to 0.48 mV/K of the layers suggest their possible application in thermoelectric converters as well.