Cubic and orthorhombic SnS thin‐film absorbers for tin sulfide solar cells

Abstract

The tin sulfide solar cell has acquired prominence in recent years. We present the characteristics of two polymorphs of SnS and their perspectives in thin‐film solar cells. Thin‐film SnS with cubic crystalline structure (SnS‐CUB) was obtained via two chemical routes. This semiconductor is distinct from the more common SnS thin films of orthorhombic crystalline structure (SnS‐ORT), also obtained by chemical routes. The SnS‐CUB reported here with a lattice constant a of 11.587 Å replaces the zinc blende structure previously reported for this material with a of 5.783 Å. Thin films of SnS‐CUB have an optical bandgap (Eg) of 1.66–1.72 eV and electrical conductivity (σ) of 10−6 Ω−1 cm−1. These characteristics distinguish them from SnS‐ORT presented here with an Eg of 1.1 eV and σ typically higher by two orders of magnitude. We discuss the uncertainties that have prevailed in the assignment of crystalline structure for SnS‐CUB and SnS‐ORT. The optical and electrical properties of these two polymorphs of SnS are contrasted in the context of light‐generated current density in solar cells. We conclude that the two SnS polymorphs when considered together as optical absorbers offer wider prospects for tin sulfide thin‐film solar cells.

Cubic‐structured tin selenide thin film as a novel solar cell absorber

“…The bottom panel in Fig. shows the peak positions – 2 θ and relative intensities of SnS‐CUB, reported previously from our group and the top panel provides the results for SnSe‐CUB of Fig. from the present work (see Supporting Information).…”

“…The patterns in Fig. (c) have similarity with the XRD pattern of SnS‐CUB base film of large simple cubic crystalline structure . Details of the structural assignment for this polymorph of SnS identified in the year 2015 are available in Refs.…”

“…Substrate layer thin film of SnS‐CUB was deposited on Corning microscope glass slides (25 × 75 mm 2 , 1 mm in thickness), which were treated overnight in a dilute Na 2 S solution. This substrate treatment described for the chemical deposition of SnSe thin films leads to the deposition of compact specularly reflective thin films of SnSe‐ORT or SnS‐CUB . The method for the deposition of SnS‐CUB thin film base layer was described in Ref.…”

“…This cube edge is twice as large as that of SnS‐rock salt (RS) structure ( a = 5.8 Å) deposited on alkali halide crystals , on which is based its powder diffraction file PDF 01‐077‐3356. The contrasting feature of SnS‐CUB with SnS‐ORT is its significantly higher E g of 1.7 eV . Solar cells of SnS‐CUB thin films have a relatively higher open circuit voltage ( V oc ) of 0.454 V compared with values less than 0.400 V for SnS‐ORT solar cells, but their η of 1.27% reported so far is inferior to that of the latter .…”

Metastable cubic tin sulfide: A novel phonon-stable chiral semiconductor

“…16 The assignment was further supported by X-ray diffraction data. 15 The cubic phase has reported optical bandgaps ranging from 1.6 to 1.8 eV, 11,13,17 and has been used to make a working solar cell. 18 Starting from the reported crystal structure parameters, we performed a local optimization of the structure (lattice vectors and internal positions) within density-functional theory (DFT) following a quasi-Newton minimization procedure.…”