Dataset Information

Two-Stage Ultraviolet Degradation of Perovskite Solar Cells Induced by the Oxygen Vacancy-Ti⁴⁺ States.

ABSTRACT: The failure of perovskite solar cells (PSCs) under ultraviolet (UV) irradiation is a serious barrier of commercial utilization. Here, a two-stage degradation process of TiO₂-based PSCs is discovered under continuous UV irradiation in an inert atmosphere. In the first decay stage, oxygen vacancy-Ti³⁺ (Ti³⁺-V_O) transform into active Ti⁴⁺-V_O trap states under UV excitation and cause photocarrier loss. Furthermore, Ti⁴⁺-V_O states can convert back into Ti³⁺-V_O states through oxidizing I^-, which result in the accumulation of I₃^-. Sequentially, the rapid decomposition of perovskite accelerated by increasing I₃^- replaces the photocarrier loss as the dominant mechanism leading to the second decay stage. Then, a universal method is proposed to improve the UV stability by blocking the transformation of Ti³⁺-V_O states, which can be realized by polyethyleneimine ethoxylated (PEIE) modified layer. The optimized devices remain ?75% of its initial efficiency (20.51%) under UV irradiation at 72 days, whereas the normal devices fail completely.

SUBMITTER: Ji J

PROVIDER: S-EPMC7160572 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Two-Stage Ultraviolet Degradation of Perovskite Solar Cells Induced by the Oxygen Vacancy-Ti4+ States.

Ji Jun J Liu Xin X Jiang Haoran H Duan Mingjun M Liu Benyu B Huang Hao H Wei Dong D Li Yingfeng Y Li Meicheng M

iScience 20200327 4

The failure of perovskite solar cells (PSCs) under ultraviolet (UV) irradiation is a serious barrier of commercial utilization. Here, a two-stage degradation process of TiO2-based PSCs is discovered under continuous UV irradiation in an inert atmosphere. In the first decay stage, oxygen vacancy-Ti3+ (Ti3+-VO) transform into active Ti4+-VO trap states under UV excitation and cause photocarrier loss. Furthermore, Ti4+-V<s ...[more]

PMID: 32299056

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Project description:The catalytic performance with high conversion and high selectivity of Ti-based oxide catalysts have been widely investigated. Besides, stability, which is an essential parameter in the industrial process, lacked fundamental understanding. In this work, we combined computational and experimental techniques to provide insight into the deactivation of P25 and TS-1 Ti-based oxide catalysts during the methyl oleate (MO) epoxidation. The considered deactivation mechanisms are fouling and surface oxygen vacancy (OV). The fouling causes temporary catalyst deactivation through active site blockage but can be removed via calcination in air at high temperature. However, in this work, the OV formation plays an important role in the overall performance of the spent catalyst as the deactivated catalyst after regeneration, cannot be restored to the initial activity. Also, the effects of OV in spent catalysts caused (i) the formation of more Ti3+ species on the surface as evident by XPS and Bader charge analysis, (ii) the activity modification of the active region on the catalyst surface as the reduction in energy gap (Eg) occurred from the formation of the interstates observed in the density of states profiles of spent catalyst modeled by the O-vacant P25 and TS-1 models. This reduction in Eg affects directly the strength of Ti-OOH active site and MO bonding, in which high binding energy contributes to a low conversion because the MO needed an O atom from Ti-OOH site to form the methyl-9,10-epoxy stearate. Hence, the deactivation of the Ti-based oxide catalysts is caused not only by the insoluble by-products blocking the active region but also mainly from the OV. Note that the design of reactive and stable Ti-based oxide catalysts for MO epoxidation needed strategies to prevent OV formation that permanently deactivated the active region. Thus, the interrelation and magnitude between fouling and OV formation on catalyst deactivation will be investigated in future works.

Dataset Information

Two-Stage Ultraviolet Degradation of Perovskite Solar Cells Induced by the Oxygen Vacancy-Ti⁴⁺ States.

Publications

Two-Stage Ultraviolet Degradation of Perovskite Solar Cells Induced by the Oxygen Vacancy-Ti<sup>4+</sup> States.

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