Bismuth trisulfide (Bi2S3)

Basic Info

Bismuth trisulfide (Bi2S3) has an orthorhombic crystal structure with 4 molecules per unit cell. Each molecule contains two bismuth atoms and 3 sulfide atoms which add up to 20 atoms per unit cell. Bi2S3 occurs naturally in the form of bismuthinite, which has a lead-gray streaked color with a metallic luster. The mineral is primarily found in Bolvia, Peru, central Europe, Austrailia, and the western United States. Bismuthinite is mainly processed to obtain pure bismuth metal or other bismuth compounds, but has also been researched for the use in photovoltaics. [1]

Crystal Structure

 

  Fractional Coordinates Orthogonal Coordinates
  Label Elmt x y z xor[Å] yor[Å] zor[Å]
1. T1 Bi 0.5165 0.2500 0.1748 -3.914 2.533 4.141
2. T1 Bi 0.9835 0.7500 0.6748 -6.849 8.734 8.119
3. T1 Bi 0.4835 0.7500 0.8252 -2.532 9.931 4.286
4. T1 Bi 0.0165 0.2500 0.3252 0.403 3.729 0.308
5. T2 Bi 0.6596 0.7500 0.4655 -3.971 6.133 6.169
6. T2 Bi 0.8404 0.2500 0.9655 -6.946 11.534 5.081
7. T2 Bi 0.3404 0.2500 0.5345 -2.475 6.331 2.258
8. T2 Bi 0.1596 0.7500 0.0345 0.501 0.930 3.347
9. T3 S 0.6230 0.7500 0.0575 -3.543 1.609 6.617
10. T3 S 0.8770 0.2500 0.5575 -7.157 7.076 6.051
11. T3 S 0.3770 0.2500 0.9425 -2.902 10.855 1.810
12. T3 S 0.1230 0.7500 0.4425 0.711 5.387 2.376
13. T4 S 0.7153 0.2500 0.3063 -5.681 4.163 5.333
14. T4 S 0.7847 0.7500 0.8063 -5.151 9.999 6.471
15. T4 S 0.2847 0.7500 0.6937 -0.764 8.301 3.095
16. T4 S 0.2153 0.2500 0.1937 -1.294 2.464 1.957
17. T5 S 0.4508 0.7500 0.3730 -2.127 4.923 4.839
18. T5 S 0.0492 0.2500 0.8730 -0.027 9.789 -0.410
19. T5 S 0.5492 0.2500 0.6270 -4.319 7.540 3.589
20. T5 S 0.9508 0.7500 0.1270 -6.418 2.674 8.838

 

The graph below shows peak intensities for Bi2S3:

 

PV Applications

Bi2Si3 thin films are prepared from several methods which include: Cathodic electrodeposition, anodic electro deposition, vacuum evaporation, hotwall method, solution-gas interface, spray deposition, and chemical bath deposition. The most common method for Bi2Si3 prepared films is chemical bath deposition. This is because it is simple, economic, and well suited for a large area of any configuration. [2]

Bi2Si3 thin films prepared from chemical bath deposition reach fill factors around 46.77% and a  conversion efficiency of 0.089%. [3]

Basic Parameters at 300 K

Crystal structure: Orthorhombic  [4]
Group of symmetry: Pnma [4]
Number of atoms in 1 cm3: 3.99*1026 [4]
Unit cell volume: 501.6730 Å3 [5]
Atoms per unit cell:  20 [4]
Density: 6.807 g/cm3 [4]
Dielectric constant: ɛ(0)|| = 120  T=300K , at 1kHz [5]
ɛ(0)⊥ = 38   T=300 K, E ⊥ c
ɛ(∞)|| = 13    T=300 K, E || c 
ɛ(∞) ⊥ = 9    T=300, 90 K, E ⊥ c
Lattice constants: a = 11.305 Å [4]
b = 3.981 Å
c = 11.147 Å 

 

 

Band Structure and carrier concentration

 

            Graph of carrier concentration may be found in [6]

Donors and Acceptors

                Impurities: Pb, Cu, Fe, As, Sb, Se, Te                                                                                                       [7]

Electrical Properties

        Basic Parameters of Electrical Properties

Energy gap: 1.3 eV T=300 K, E ⊥ b: [5]
1.45 eV T=77 K, E ⊥ b
Intrinsic carrier concentration: : n = 3 × 1018 cm-3 T = 300 K : [5]
Carrier mobility: : μn = 200 cm2/Vs T=300 K : [5]
Hole mobility: : μh = 1100 cm2/Vs : [8]
Intrinsic resistivity: : ρ = 105 Ω cm T=300K: [2]
Electrical Conductivity: : σ = 10-6…10-7 Ω-1 cm-1 T=300 K: [5]

Optical properties

Refractive indices:

λ = 589.3 nm                       [5]

nα 1.315
nβ 1.900
nγ 1.670

Absorption coefficient:                 α = 104 cm-1 (In the order of)                      [2]

Graph of optical transimttance data may be found in:[9]

Mechanical properties, elastic constants, lattice vibrations Basic Parameters

Hardness:     2-2.5 [7]
Cleavage planes:  Perfect on (010)   [7]
  Imperfect on (100), (110) Ralph2003

 

The development of these pages on photovoltaic materials’ properties was carried out at the University of Utah primarily by undergraduate students Jeff Provost and Carina Hahn working with Prof. Mike Scarpulla. Caitlin Arndt, Christian Robert, Katie Furse, Jash Sayani, and Liz Lund also contributed. The work was fully supported by the US National Science Foundation under the Materials World Network program award 1008302. These pages are a work in progress and we solicit input from knowledgeable parties around the world for more accurate or additional information. Contact earthabundantpv@eng.utah.edu with such suggestions. Neither the University of Utah nor the NSF guarantee the accuracy of these values.