Photoluminescence Tuning Through Irradiation Defects in CH₃NH₃PbI₃ Perovskites

Abstract

Defect engineering is applied to hybrid (CH 3 NH 3 )PbI 3 organic-inorganic perovskites. These materials have become one of the most promising lowcost alternatives to traditional semiconductors in the field of photovoltaics and light emitting devices. Here Helium ion irradiation at low energy has been used as a tool for the controlled introduction of point defects in both single crystals and polycrystalline thin films. The irradiation defects modify the opto-electronic properties as probed using photoluminescence (PL) spectroscopy from 10 K to room-temperature. Contrary to usual semiconductors, a very good resilience of the PL properties with irradiation is observed, even associated to an enhancement of the optical emission at low temperature. These results are discussed in relation with the tetragonal to orthorhombic low-temperature phase transition below T ¼ 160 K. A comparison between spectra from single crystals and polycrystalline films, both with and without irradiation defects, allows a better understanding of the light emission mechanisms in both kinds of samples. The authors thereby evidence radiation hardness of these materials and the specificity of defects and their impact on light emission properties.

Reversible Photoinduced Phase Segregation and Origin of Long Carrier Lifetime in Mixed‐Halide Perovskite Films

“…The low-energy asymmetry in PL emission is related to presence of bound excitons and shallow energy levels by iodine interstitials defects. [36,37] Figure 5b shows the semilog scale temperature dependent PL spectra of demixed stage measured at high power-density (840 mW cm −2 ). For demixed stage dynamics, first sample was illuminated at high power (840 mW cm −2 ) at room temperature to create phase segregated domains and then cooled down to 10 K under continuous photoexcitation.…”

“…5 (a) shows the temperature-dependent PL spectra of mixed stage (parent phase), on a semi-logarithmic scale measured at low excitation power-density (< 1 mW/cm 2 ) and exhibits a single emission peak with low energy asymmetry at low-temperature (10 K). The lowenergy asymmetry in PL emission is related to presence of bound excitons and shallow energy levels by iodine interstitials defects [37,38]. Fig 5 (b) shows the semi-log scale temperature dependent PL spectra of demixed stage measured at high power-density (840 mW/cm 2 ).…”

Strain and Optoelectronic Tuning in Mixed‐Halide Perovskites with Ion Irradiation

“…We have introduced on purpose different defect concentrations into TC‐MHP polycrystalline thin films, of composition (MA 0.17 FA 0.83 ) 0.95 Cs 0.05 Pb(I 0.83 Br 0.17 ) 3 , with proton irradiation at 1 MeV and different fluences from 10 13 cm −2 to 5 × 10 15 cm −2 . Contrary to usual semiconductors, where irradiation defects quench the luminescence very efficiently, it was already observed that hybrid perovskite samples, both in single crystals and polycrystalline thin films, present high radiation hardness under Helium ion irradiation using low energy at 30 keV [ 22 ] or proton irradiation at 50 keV. [ 23 ] We estimated, for instance, that these compounds were about 10 5 times more radiation‐hard than crystalline silicon.…”

Halide Perovskite Excitonic Diffraction Grating

“…Irradiation of CsPbBr 3 and MAPbI 3 (MA + = CH 3 NH$$_3^ + $$) halide perovskites with such doses of 30 keV Ga + or He + ions leads to the formation of defect serving as radiative recombination centers. [ 28–30 ] The irradiation with meV ion beams leads to the increase in the emission of MAPbBr 3 . [ 31 ] Such behavior could be explained by the well‐known defect tolerance of these materials [ 32 ] which gives hope for the possibility of careful modulation of excitonic properties by FIB.…”