研究目的
Investigating the self-healing mechanism of photocurrent degradation in perovskite solar cells under solar illumination.
研究成果
The study provides a first-principles theory that elucidates the key experimental observations on light-activated photocurrent degradation and self-healing in MAPbI3. It reveals that structural changes upon photoexcitation lead to the formation of localized excitons trapped at defects, resulting in photocurrent degradation. The theory explains the contrasting dynamics between photo-degradation and recovery and predicts similar behavior in other lead halide perovskites with faster recovery dynamics.
研究不足
The study is limited by the computational costs of the OT-RSH calculations, which restrict the vacancy concentration to a high level. Additionally, the dynamics of space charge accumulation/disappearance, which determines the photocurrent degradation/recovery, is not estimated from first-principles.
1：Experimental Design and Method Selection:
The study employs first-principles calculations based on time-dependent density functional theory (TDDFT) to investigate the role of defect-trapped excitons in the photocurrent degradation and self-healing processes in perovskite solar cells.
2：Sample Selection and Data Sources:
The study focuses on two representative point defects - lead and iodine vacancies - in four lead halide perovskites APbX3 (A = methylammonium, MA or formamidinium, FA; and X = I or Br).
3：List of Experimental Equipment and Materials:
Computational methods and software tools for first-principles calculations are used, including the optimally tuned and range-separated hybrid (OT-RSH) functional and Perdew-Burke-Ernzerhof functional with spin-orbital coupling (SOC).
4：Experimental Procedures and Operational Workflow:
The study involves geometric relaxation in the ground state of the perovskite, followed by relaxation in the excited state using TDDFT to capture electron-hole and electron/hole-nuclei interactions.
5：Data Analysis Methods:
The density of states (DOS) and potential energy surfaces (PESs) are calculated to analyze the formation of deep trap states and the dynamics of exciton trapping and de-trapping.
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