Abstract
The wide‐bandgap methylammonium lead bromide perovskite is promising for applications in tandem solar cells and light‐emitting diodes. Despite its utility, there is a limited understanding of its reproducibility and stability. Herein, the dependence of the properties, performance, and shelf storage of thin films and devices on minute changes to the precursor solution stoichiometry is examined in detail. Although photovoltaic cells based on these solution changes exhibit similar initial performance, shelf storage depends strongly on precursor solution stoichiometry. While all devices exhibit some degree of healing, bromide‐deficient films show a remarkable improvement, more than doubling in their photoconversion efficiency. Photoluminescence spectroscopy experiments performed under different atmospheres suggest that this increase is due, in part, to a trap‐healing mechanism that occurs upon exposure to the environment. The results highlight the importance of understanding and manipulating defects in lead halide perovskites to produce long‐lasting, stable devices.
Highlights
Hybrid organic-inorganic lead halide perovskites have earned a lot of research attention in the past decade due to their broad-spectrum absorption and efficient photocurrent generation in solar cells, with record performances reaching those of silicon (24.2% photoconversion efficiency, PCE, at the time of writing)[1]
While solar cells using methylammonium lead tribromide (MAPbBr3) perovskites show much lower PCE, its wide band gap and corresponding high VOC offer the potential for inclusion into tandem cells, where a MAPbBr3 absorber is combined with a narrow band gap material in order to collect additional photons and achieve higher performance[18,19,20]
We carefully examine the effect of precursor solution stoichiometry on the properties, performance and storage stability of MAPbBr3 thin-films and devices
Summary
Hybrid organic-inorganic lead halide perovskites have earned a lot of research attention in the past decade due to their broad-spectrum absorption and efficient photocurrent generation in solar cells, with record performances reaching those of silicon (24.2% photoconversion efficiency, PCE, at the time of writing)[1]. The composition of the active layer plays an important role, with multi-cation compositions showing an overall higher stability[11,12,13] Even upon taking these factors into account, literature reports concerning device stability vary greatly even for devices fabricated from the same recipe in the same device architecture[14]. We showed that purposefully adjusting the ratio between the precursor components (methylammonium iodide (MAI) and lead acetate trihydrate (Pb(Ac)2)) in small, almost negligible amounts, results in large variations in the subsequent photovoltaic (PV) performance and stability[16] These stoichiometric variations are correlated with the photoluminescence (PL) behavior of the MAPbI3 thin films, displaying significant differences in both the initial PL quantum efficiency (PLQE) and its evolution after exposure to light and oxygen[17]. Our results underline the strong role that film composition plays in defining the properties, performance, and stability of devices, and further promote the idea that defect engineering may be a viable strategy to produce desirable properties in perovskites
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