Absorption spectra of perovskites

We calculate the optical properties of a set of oxides, oxynitrides, and organometal halide cubic and layered perovskites with a bandgap in the visible part of the solar spectrum.

Ivano E. Castelli, Kristian S. Thygesen, and Karsten W. Jacobsen

Calculated optical absorption of different perovskite phases.

Journal of Materials Chemistry A, printed online.

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Key-value pairs

key	description	unit
data.energy	Grid used to calculate the Re and Im part of epsilon	eV
data.im_eps	Im(epsilon) in xyz direction
data.re_eps	Re(epsilon) in xyz direction
eff	Calculated efficiency (thickness 1 nm)	eV
eff_max	Calculated efficiency (infinite thickness)	eV
gllbsc_dir_gap	Direct bandgap calculated with GLLB-SC	eV
gllbsc_disc	Derivative discontinuity calculated with GLLB-SC	eV
gllbsc_ind_gap	Indirect bandgap calculated with GLLB-SC	eV
name	Name of the structure
phase	Perovskite phase (cubic halides (cubic tetragonal orthorhombic) RP DJ)
project	project

Absorption spectrum of AgNbO3

# creates: spectrum.svg
"""Plot the absorption spectrum along the x direction for a given
perovskite"""

import matplotlib.pyplot as plt
import ase.db

# Connect to database:
c = ase.db.connect('absorption_perovskites.db')

# Select cubic symmetry containing Sn:
for n in c.select('name=AgNbO3'):
    name = n.name
    energy = n.data.energy
    im_eps_x = n.data.im_eps[0]
plt.plot(energy, im_eps_x)

plt.arrow(n.gllbsc_dir_gap,
          2,
          0.0,
          -1,
          fc="g",
          ec="g",
          head_width=0.2,
          head_length=0.3,
          head_starts_at_zero=False)

plt.text(n.gllbsc_dir_gap,
         2.1,
         'gap_d',
         rotation=90,
         horizontalalignment='center',
         verticalalignment='bottom',
         color='g')
if (n.gllbsc_dir_gap != n.gllbsc_ind_gap):
    plt.arrow(n.gllbsc_ind_gap,
              2,
              0.0,
              -1,
              fc="r",
              ec="r",
              head_width=0.2,
              head_length=0.3,
              head_starts_at_zero=False)
    plt.text(n.gllbsc_ind_gap,
             2.1,
             'gap_i',
             rotation=90,
             horizontalalignment='center',
             verticalalignment='bottom',
             color='r')

plt.ylabel('Abs. Spectrum [arb. units]')
plt.xlabel('Energy [eV]')
plt.text(7, 0.5, name)
plt.savefig('spectrum.svg')

Calculated efficiencies of the cubic phase perovskites

This script requires the perfect absorption limit:

• Download perfect absorption limit

# creates: efficiency.svg
"""Plot the efficiencies of a perovskite phase (cubic in the example
here)"""

import matplotlib.pyplot as plt
import ase.db

# Connect to database:
c = ase.db.connect('absorption_perovskites.db')

o = open('perfect_abs.txt', 'r')
lines = o.readlines()
o.close()

en = []
perf_abs = []
for line in lines:
    line = line.split()
    en.append(float(line[0]))
    perf_abs.append(float(line[2]) / 4.30E+21)

for n in c.select('phase=cubic'):
    if 'O3' in n.name:
        color = 'black'
        symb = 'o'
    if 'O2N' in n.name or 'ON2' in n.name:
        color = 'red'
        symb = 's'
    if 'O2F' in n.name:
        color = 'blue'
        symb = 'D'

    plt.plot([n.gllbsc_ind_gap, n.gllbsc_ind_gap],
             [n.eff, n.eff_max],
             '-' + symb,
             color=color)
    plt.text(n.gllbsc_ind_gap - 0.025, n.eff, n.name,
             color=color,
             fontsize=12,
             rotation=90,
             horizontalalignment='center',
             verticalalignment='bottom')

plt.plot(en, perf_abs, '--', color='green')
plt.plot(2.5, 0.32, 'o', color='black')
plt.plot(2.5, 0.29, 's', color='red')
plt.plot(2.5, 0.26, 'D', color='blue')
plt.text(2.55,
         0.32,
         'Oxides',
         color='black',
         fontsize=16,
         horizontalalignment='left',
         verticalalignment='center')
plt.text(2.55,
         0.29,
         'Oxynitrides',
         color='red',
         fontsize=16,
         horizontalalignment='left',
         verticalalignment='center')
plt.text(2.55,
         0.26,
         'Oxyfluorides',
         color='blue',
         fontsize=16,
         horizontalalignment='left',
         verticalalignment='center')
plt.text(1.3,
         0.33,
         'Cubic',
         color='black',
         fontsize=16,
         horizontalalignment='left',
         verticalalignment='center')
plt.xlim(1.2, 3.1)
plt.ylim(0, 0.35)
plt.xlabel('Bandgap [eV]', fontsize=18)
plt.ylabel('Absorbed Photons [%]', fontsize=18)
plt.xticks([1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0],
           ['1.4', '1.6', '1.8', '2.0', '2.2', '2.4', '2.6', '2.8', '3.0'],
           fontsize=16)
plt.yticks([0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3],
           ['0', '5', '10', '15', '20', '25', '30'],
           fontsize=16)
plt.savefig('efficiency.svg')