Photoconductive thin films of AgSbS₂ with cubic crystalline structure in solar cells

Abstract

Polycrystalline thin films of AgSbS2 of thickness 140 nm and crystalline structure matching that of the mineral cuboargyrite (a = 0.5652 nm) are obtained by heating chemically deposited thin films at 150–320 °C. These films are deposited at 40 °C from a solution mixture containing antimony‐thiosulfate complex and Ag‐nitrate at a mole‐fraction Ag/(Ag+Sb) of 0.31. The as‐deposited films are progressively transformed to cubic‐AgSbS2, with the fraction of crystalline matter at 3.7% after heating at 150 °C and 98% at 280 °C. The crystalline grain diameter is limited to 8–11 nm. The amorphous film has an optical band gap (Eg) of 2.03 eV and the film heated at 320 °C has an Eg of 1.79 eV. The crystalline films are photoconductive; with electrical conductivity of 10−5 Ω−1 cm−1 under an intensity of illumination, 1000 W m−2 (tungsten‐halogen). The mobility–lifetime product of the material is 7.5 × 10−7 cm2 V−1. A solar cell, SnO2:F/CdS/AgSbS2(420 nm)/C, has open circuit voltage, 0.615 V; short‐circuit current density, 1.67 mA cm−2; and conversion efficiency, 0.57% for air‐mass 1.5 global solar radiation. Estimate for the maximum photo‐generated current density for cubic‐AgSbS2 is 16 mA cm−2; hence a supplementary absorber is recommended for future development of the solar cell.

Facet‐Specific Ligand Interactions on Ternary AgSbS2 Colloidal Quantum Dots

“…The band gaps of AgSbS 2 QDs with diameter 18.5, 10.5, and 6.5 nm were calculated as 2.0, 2.25, and 2.51 eV, respectively. These values are larger than the band gap of 1.74 eV in the bulk, indicating that all three samples exhibit quantum confinement. However, these band gaps for the similar sizes are somewhat different from the AgSbS 2 QDs reported by Zhou et al .…”

Silver Antimony Sulfide Selenide Thin‐Film Solar Cells via Chemical Deposition

“…This is indicative of an amorphous‐to‐crystalline conversion of the thin film, as reported in the study by Capistran‐Martínez. [ 9 ] Figure 1c shows the as‐deposited FTO/CdS, after its heating at 350 °C in air, and with Ag−Sb−S thin film of 700 nm in thickness, we obtained in two consecutive depositions, as shown in Figure 1b.…”

“…The Ag/Sb mole ratio in this solution was (0.7 mmol Ag)/(2.28 mmol of Sb) = 0.307, which was found to produce AgSbS 2 films when the films were heated, without excess phases. [ 9 ] The chemical deposition of thin films of ternary compositions took place from the dissociation of Ag and Sb thiosulfate complexes depending on the solubility products of the salts (Ag 2 S: 6 × 10 −55 mol 3 L −3 and Sb 2 S 3 : 2 × 10 −93 mol 5 L −5 ) and the dissociation of Ag and Sb complexes. This involved detailed chemical equilibria, [ 19 ] but it is not specifically addressed so far for the present case.…”

“…The as‐deposited Ag−Sb−S film produced by this method was amorphous to X‐rays, without any well‐defined peaks of a crystalline material. [ 9 ] Heating the films at temperatures above 180 °C converted them from its appearance as yellowish−orange (as‐prepared) in transmitted daylight to reddish−brown. This is indicative of an amorphous‐to‐crystalline conversion of the thin film, as reported in the study by Capistran‐Martínez.…”

“…Solar cells of either AgSbS 2 or AgSbSe 2 have not reached significant efficiencies ( η > 3%), for airmass 1.5 global solar radiation (AM1.5G)‐to‐electric energy conversion, to be recongnized as “emerging solar cells.” [ 3 ] Among the best AgSbS 2 thin‐film solar cells is a liquid‐junction cell [ 8 ] and the one developed on flourine‐doped SnO 2 (FTO) in the structure: FTO/CdS(100 nm)/AgSbS 2 (420 nm)/C‐Ag, reported in this journal in 2015. [ 9 ] With an active cell area of 0.36 cm 2 , it showed under standard conditions an open‐circuit voltage ( V oc ) of 0.615 V, short‐circuit current density ( J sc ) of 1.67 mA cm −2 , fill factor (FF) of 0.54, and η of 0.55%. The chemical deposition reported there was a modification of the method used for depositing Sb 2 S 3 thin films, [ 10 ] which also served as a precursor film to produce CuSbS 2 film, [ 11 ] Sb 2 S 3 /CuSbS 2 solar cells, [ 12 ] and InSb thin films.…”