Low-temperature luminescence in organic-inorganic lead iodide perovskite single crystals
I. V. Zhevstovskikh, N. S. Averkiev, М. Н. Сарычев, O. I. Semenova, О. Е. Терещенко
Abstract
Abstract We present a temperature and laser-power dependent photoluminescence (PL) study of methylammonium lead iodide (CH 3 NH 3 PbI 3 ) single crystals in the orthorhombic phase. At temperatures below 140 K, we revealed the multi-component PL emission. In addition to a free exciton with an energy of 1.65 eV, we found emission bands with peaks approximately equal to 1.6 eV, 1.52 eV, and 1.48 eV. Analysis of the thermal evolution of the intensities, peak positions, and linewidths of all the PL bands allowed one to determine their origin. We attributed the PL peak with energy of 1.6 eV to a bound exciton, while the free exciton-bound exciton splitting energy is 50–60 meV. The PL emission with an energy of 1.52 eV can be explained by the donor-acceptor pair (DAP) recombination, where donor and acceptor defects have a depth of about 12 meV and 120 meV, respectively. MA (CH 3 NH 3 ) interstitials (MA <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mi/> <mml:mi>i</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> </mml:math> ) and lead vacancies (V <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mi/> <mml:mrow> <mml:mi mathvariant="normal">P</mml:mi> <mml:mi mathvariant="normal">b</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> <mml:mo>−</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> ) are the most suitable for the DAP transition to occur in CH 3 NH 3 PbI 3 crystals. The 1.48 eV PL emission is consistent with the recombination of self-trapped excitons, and interstitial iodine is likely to be an active trap source. We found the variation of the self-trapped depth from 15 meV (at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>T</mml:mi> <mml:mo><</mml:mo> </mml:math> 80 K) to 53 meV (at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>T</mml:mi> <mml:mo>></mml:mo> </mml:math> 80 K) with increasing the temperature. Although the multi-component PL emission in CH 3 NH 3 PbI 3 single crystals appears at low temperatures, defects and excitonic traps that cause this emission can affect the photophysics of hybrid perovskites at higher temperatures.