Lead Halide Perovskite Based Functional Materials for Photodetectors and Light-Emitting Films
滷化鈣鈦礦功能材料在光電探測器和光致發光薄膜的應用
Student thesis: Doctoral Thesis
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Detail(s)
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| Award date | 25 Aug 2021 |
Link(s)
| Permanent Link | https://scholars.cityu.edu.hk/en/theses/theses(00621b7b-aecc-4013-b9fa-64f0f9d22bfa).html |
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| Other link(s) | Links |
Abstract
In recent years, lead halide perovskites materials have attracted substantial interest due to the excellent optoelectronic performance which includes long carrier diffusion length, high absorption coefficient, tunable bandgap, and due to their facile processability. These outstanding properties make lead halide perovskites promising for applications in solar cells, photodetectors, lasers and light-emitting diodes. In this thesis, we developed different strategies to produce lead halide perovskite films for their use in photodetectors and light-emitting structures. We also studied proton transfer process in bulk (3D) lead halide perovskites with long-chain alkyl amines, which provided a facile route to transform them into 2D Ruddlesden–Popper perovskites.
In chapter 1 (Introduction), we introduce luminescent perovskite nanocrystals and 2D Ruddlesden–Popper perovskites, with an emphasis on the synthetic methods and material structures. Morphology of the perovskites films which are produced from those materials can be well controlled by applying methods such as hot-injection, template-assistant growth, spin-coating and doctor-blading. This is followed by a comprehensive overview of recent progress on the metal halide perovskites-based photodetectors. We summarize the optoelectronic characteristics of the perovskite-based photodetectors according to the different categories of perovskite active layers.
In chapter 2, we adapted a facile solution-based anti-solvent strategy to fabricate a hybrid structure comprising CuInSe2 quantum dots embedded in a methylammonium lead iodide (MAPbI3) perovskite matrix. Stability of this hybrid structure was significantly improved due to the presence of the hydrophobic ligands from the CuInSe2 quantum dots acting as a barrier against the uptake of environmental moisture. Based on this MAPbI3/ CuInSe2 composite, broadband photodetectors have been produced with a high responsivity of > 0.5 A/W and 10.4 mA/W in the visible and near-infrared spectral ranges, and a large on/off ratio of 104 at 2 V bias.
In chapter 3, we demonstrate how a fast proton transfer process between the organic moiety in 3D methylammonium lead halide perovskites and introduced aliphatic alkylamines can provide a facile and efficient route to prepare 3D/2D hybrid perovskites. By separately introducing five different alkylamines into toluene as antisolvents (butylamine, octylamine, dodecylamine, hexadecylamine and octadecylamine), they were quickly protonated during the spin-coating process and interacted with lead halide slabs in the developing perovskite films through hydrogen bonds. This led to the formation of mixed 3D/2D hybrid perovskites, where the ratio between the 3D and 2D RP phases could be tuned by adjusting the concentration of the added alkylamines.
In chapter 4, we used octadecylamine dissolved in toluene which served as an antisolvent to form brightly emitting formamidinium lead bromide perovskite films. During the spin-coating process, the proton transfer process occurred between octadecylamine and perovskite, which has again resulted in formation of 3D/2D hybrid perovskites, in this case formamidinium based ones. Remarkably, obtained 3D/2D perovskite films showed an exceptionally high photoluminescence quantum yield of over 90%, which was ascribed to the passivating action of octadecylamine and the formation of 2D perovskite phases. Moreover, octadecylamine protected the perovskite films from moisture penetration, so that non-encapsulated films could even maintain their emission in water.
In chapter 5, we summarize and highlight the major outcomes of these studies. By using narrow-bandgap CuInSe2 quantum dots, the performance of the broadband perovskite-based devices can be significantly improved. When the alkylamines dissolved in toluene were used as antisolvents, they could transform 3D methylammonium and formamidinium lead halide perovskites into layered 2D phases. We also provide an outlook for lead halide perovskite-based materials and devices in terms of current issues and possible approaches to address and to solve them.
In chapter 1 (Introduction), we introduce luminescent perovskite nanocrystals and 2D Ruddlesden–Popper perovskites, with an emphasis on the synthetic methods and material structures. Morphology of the perovskites films which are produced from those materials can be well controlled by applying methods such as hot-injection, template-assistant growth, spin-coating and doctor-blading. This is followed by a comprehensive overview of recent progress on the metal halide perovskites-based photodetectors. We summarize the optoelectronic characteristics of the perovskite-based photodetectors according to the different categories of perovskite active layers.
In chapter 2, we adapted a facile solution-based anti-solvent strategy to fabricate a hybrid structure comprising CuInSe2 quantum dots embedded in a methylammonium lead iodide (MAPbI3) perovskite matrix. Stability of this hybrid structure was significantly improved due to the presence of the hydrophobic ligands from the CuInSe2 quantum dots acting as a barrier against the uptake of environmental moisture. Based on this MAPbI3/ CuInSe2 composite, broadband photodetectors have been produced with a high responsivity of > 0.5 A/W and 10.4 mA/W in the visible and near-infrared spectral ranges, and a large on/off ratio of 104 at 2 V bias.
In chapter 3, we demonstrate how a fast proton transfer process between the organic moiety in 3D methylammonium lead halide perovskites and introduced aliphatic alkylamines can provide a facile and efficient route to prepare 3D/2D hybrid perovskites. By separately introducing five different alkylamines into toluene as antisolvents (butylamine, octylamine, dodecylamine, hexadecylamine and octadecylamine), they were quickly protonated during the spin-coating process and interacted with lead halide slabs in the developing perovskite films through hydrogen bonds. This led to the formation of mixed 3D/2D hybrid perovskites, where the ratio between the 3D and 2D RP phases could be tuned by adjusting the concentration of the added alkylamines.
In chapter 4, we used octadecylamine dissolved in toluene which served as an antisolvent to form brightly emitting formamidinium lead bromide perovskite films. During the spin-coating process, the proton transfer process occurred between octadecylamine and perovskite, which has again resulted in formation of 3D/2D hybrid perovskites, in this case formamidinium based ones. Remarkably, obtained 3D/2D perovskite films showed an exceptionally high photoluminescence quantum yield of over 90%, which was ascribed to the passivating action of octadecylamine and the formation of 2D perovskite phases. Moreover, octadecylamine protected the perovskite films from moisture penetration, so that non-encapsulated films could even maintain their emission in water.
In chapter 5, we summarize and highlight the major outcomes of these studies. By using narrow-bandgap CuInSe2 quantum dots, the performance of the broadband perovskite-based devices can be significantly improved. When the alkylamines dissolved in toluene were used as antisolvents, they could transform 3D methylammonium and formamidinium lead halide perovskites into layered 2D phases. We also provide an outlook for lead halide perovskite-based materials and devices in terms of current issues and possible approaches to address and to solve them.
