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First-principles investigation of molecules’ adsorption on complex surfaces of perovskites : the case of organic/inorganic perovskites for photovoltaic applications

Abstract : To study the degradation in perovskite in the ambient conditions, the adsorption of molecules such as, CO, CO2, O2 and H2O are carried out on the surfaces of organic/inorganic halide perovskites have been investigated at the first-principles level, using a hybrid exchange-correlation functional optimized to yield a description of their structural, electronic and dynamic properties, in good agreement with experiment. For the inorganic/organic halide perovskite, the CsX/MAI- and PbX2-terminated slabs without defects have been considered, and their dynamic properties determined, revealing zone-boundary phonon instabilities for q=pi/a (1,0) and pi/a (1,1) for CsPbX3 surface and for MAPI and FAPI surfaces at q=pi/a (0,0) and pi/a (1,1). After the treatment of instabilities, charge and neutral halide vacancies were created on top of the CsPbX3 surface for CsX and PbX2 terminated structures. Further on, the relaxation patterns at the surfaces due to adsorption of molecules (CO, CO2 and O2) have been studied for different docking sites, and the corresponding adsorption energies estimated for the perfect surfaces and the surfaces with vacancies for CsPbX3 compounds. For MAPI, H2O and O2 were adsorbed on MAI and PbI2 terminated structures and their corresponding adsorption energies were estimated.For the perfect surface, the CsX-terminated surfaces, CO2 was found to be more reactive than CO or O2. On the PbX2-terminated surfaces, the CO2 reactivity is two times weaker than on the CsX-terminated ones, becoming in fact comparable to that of CO and O2, the latter having the lowest adsorption energy. Upon the introduction of molecules to the charged vacancy, the adsorption energies do not see a significant impact while for the case of neutral vacancy the adsorption energy increases. H2O shows the highest adsorption energy while for neutral vacancy CO2 shows the highest adsorption energy for both types of termination. H2O in the dissociated state has higher adsorption energy than in the undissociated state. For MAPI, H2O shows higher adsorption energy and PbI2 termination comes out to be the most reactive one.The adsorption does not seem to have any significant impact on the electronic structure of the perfect CsPbX3 surfaces and surfaces with charged vacancy, whatever the perovskites, types of surfaces or molecules. However, for the case of neutral vacancy, the density of states are shifted indicating the bond formation. CO2 also loses its linearity due to the bonding between C and Pb atoms. A similar shift in the density of states is observed when water and oxygen are introduced in the dissociated state onto MAPI, indicating the formation of bonds.The obtained adsorption energies and electronic structures permit to characterize attachment of the molecules studied on the surfaces in question as physisorption for the perfect CsPbX3 surface and chemisorption for the surfaces with neutral vacancies on the CsPbX3 surface and in the case with the MAPI surface when oxygen and water were introduced in the dissociated state.
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Submitted on : Friday, May 13, 2022 - 6:12:51 PM
Last modification on : Saturday, May 14, 2022 - 3:19:32 AM

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Arpit Mishra. First-principles investigation of molecules’ adsorption on complex surfaces of perovskites : the case of organic/inorganic perovskites for photovoltaic applications. Physics [physics]. Université de Lorraine, 2021. English. ⟨NNT : 2021LORR0255⟩. ⟨tel-03667933⟩



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