本篇論文主要探討透過離子互換改變鈣鈦礦單晶鹵素成分形成可調變式窄頻光偵測器。相較於多晶薄膜來說，單晶塊擁有低缺陷密度、長擴散長度特性和較好的載子遷移率，所以單晶塊的光電特性會比多晶薄膜來的好，且因為單晶塊的厚度相對多晶薄膜厚的許多，可以有效降低元件的漏電流。本研究首先使用逆溫法長出公分等級大小之各種不同鹵素的鈣鈦礦單晶塊，經過文獻証明，不同鹵素的鈣鈦礦，在某些不同的溶劑中會有隨溫度上升溶解度下降的情形發生，例如甲基氨基溴化鉛會在二甲基甲醯胺中會有溫度上升溶解度下降的情況，此方法下，可以大幅縮短成長單晶塊所需的時間，一般單晶塊的成長需要花費的數天的時間，而逆溫法只需幾個小時的時間即可長出高品質的單晶塊。
因為單晶塊的厚度較厚，它的漏電流會相對多晶薄膜來的小，且多數波段的光暗電流比會變得相當低，只有在吸收邊界附近的光暗電流比不會被壓制，其主要原因為表面載子的附合，鈣鈦礦的高吸收常數使短波長的光穿透深度非常的小，故光激發載子會產生在頂部電極的附近，並因為表面載子複合劇烈，使光激載子非常容易淬熄。而在長波長的部分，鈣鈦礦本身對於長波長的吸收效率本來就不高，光響應理所當然不會高，為了證明表面複合機制，本研究將單晶塊利用銦球當作電極製作垂直式結構和水平式結構，在水平式結構的情況下，短波長的光暗電流比並不會被壓制，垂直式結構卻會，這證明了先前所提到的，光激載子是因為穿透深度小，使淬熄效果劇烈。
我們可以得到一個狹帶的光暗電流比在反應光譜中，這對鈣鈦礦來說是一個全新的發展。我們利用各種材料分析例如X-射線繞射分析,掃描式電子顯微鏡,近紅外/可見光/紫外光分光光譜儀來了解單晶的成分和特性。在電性方面，我們利用氙燈和分光儀來獲得單一波長. 透過照射不同的波長的光來量測單晶塊的IV特性，包括光暗電流比,外部量子效率,響應率,探測率和響應時間.最後再拿來和多晶薄膜做電性和穩定度的比較.
然而，基於包含兩種鹵素的鈣鈦礦單晶塊不易由逆溫法來成長，因此本篇提出透過離子交換的方式來長出包含兩種鹵素的鈣鈦礦單晶塊，由於甲基氨基溴化鉛和甲基氨基氯化鉛皆為立方晶系，兩種晶體的鹵素較易於不破壞晶格條件下互換，本論文便嘗試將甲基氨基氯化鉛晶體浸泡在甲基氨基溴化鉛中，發現甲基氨基氯化鉛晶體會由透明轉黃，再透過適當的升溫控制後，晶體會再由黃轉紅，從顏色上我們可以推測晶體的內部氯元素逐漸被溴元素取代，我們將晶體拿去紫外光-可見光-近紅外光分光光譜儀做吸收邊界的量測，會發現吸收邊界有紅移的現象發生，由以上敘述我們可以得知，利用晶體浸泡在其他液體的方式可以產生離子交換，並由吸收邊界得知透過不同的浸泡時間，我們可以自由的調變鈣鈦礦晶體的能隙，形成可調變的光電元件。
在使用光偵測器時，由於各類背景雜訊的關係，通常必須耦合一濾光片以增加訊號雜訊比。一般鈣鈦礦多晶薄膜的光偵測器並無濾波功能，若要達到狹帶的效果，必須用濾鏡或使用窄頻吸收的材料，但這通常會遇到價格昂貴或不易設計光學系統的問題，且濾鏡的鏡頭容易受灰塵等汙染影響，單晶塊的鈣鈦礦光檢測器可以有效解決上述的問題。搭配到浸泡其他鈣鈦礦溶液產生離子互換來調節能隙，本論文發現窄頻光暗電流比會隨著吸收邊界移動，如此便可以得到一個可調變式的窄頻光偵測器。

This research mainly discusses the formation of the tunable narrowband photodetector by changing the halogen of perovskite single crystal through ion exchange.
Comparing with the polycrystalline thin film, the bulk single crystal has low defect density, long diffusion length characteristic and better carrier mobility, is why bulk single crystal has the better photoelectric characteristics than polycrystalline film. The thickness of the bulk single crystal is thicker than the polycrystalline film, which can effectively reduce the leakage current of the device.
In this study, we first use the method of inverse temperature crystallization to grow different halogen of perovskite bulk single crystal in centimeter-size. It has been known that the solubility of different halogen perovskite will decrease with the temperature rising in some different solvents from the literature. For example, the solubility of methylamine lead bromide will decrease when temperature rise in the dimethylmethanamide (DMF) solvent. This method can significantly shorten the time required to grow a bulk single crystal.
In general, the growth of bulk single crystal takes several days, and the inverse temperature crystallization takes only a few hours to grow high- quality bulk single crystal.
Because the thickness of the bulk single crystal is thick, its leakage current will be smaller than the polycrystalline thin film, and the photo-dark current ratio (on/off ratio) of most bands will become quite low, only the on/off ratio near the absorption boundary will not be suppressed.
The main reason is the recombination of the surface carriers, the high absorption constant of the perovskite make short wavelength light penetration depth very small, so the photo-excited carrier will be generated in the vicinity of the top electrode, and because the surface carrier recombination is intense, so that photo-excited carrier is very easy to quench. While in the long wavelength part, the absorption efficiency of perovskite for long wavelengths is not high, so the photoresponse is not high.
In order to prove the mechanism of surface carrier recombination, this study will use the indium sphere as the electrode to make the vertical structure and the horizontal structure. In the case of a horizontal structure, the on/off ratio of the short wavelength is not suppressed and the vertical structure will be. These results prove that the quenching effect severe is because of the short penetration depth.
We can get a narrowband of on/off ratio in the response spectrum, which is a new development for perovskite, We use a variety of material analysis such as XRD, SEM and UV-Vis-NIR absorption spectra to understand the composition and characteristics of single crystals
In terms of electrical properties, we use Xe lamps and monochromator to achieve a single wavelength. The IV characteristics of the bulk single crystal are measured by irradiating light of different wavelengths, including on/off ratio, external quantum efficiency, responsivity, detectivity and response time, then we compare the electrical property and stability with the polycrystalline thin film.
However, it is not easy to grow the perovskite bulk single crystal which is constituted of two kinds of halogen by the inverse temperature crystallization, so this study proposed through the ion exchange way to grow two kinds of halogen containing perovskite bulk single crystal. Since methylamine lead bromide and methylamine lead chloride are all cubic systems, the halogen of two crystals is easier to exchange without any destruction.
In this thesis, we try to immerse the methylamine lead chloride crystals in methylamine lead bromide growth solution and found that the methylamine lead chloride crystals color will change from transparent to yellow, then crystals turn yellow to red by the appropriate temperature control. From the color changing, we can speculate that the crystal inside the chlorine element is gradually replaced by bromine elements
We take the crystal to the UV-Vis-NIR Spectrophotometer to do the measurement of the absorption boundary, will find the phenomenon of redshift absorption of the border.
From the above description we can see that the use of crystal immersing in other liquids can occur ion exchange and the absorption of the boundary that through different immersing time, we can adjust the band gap of perovskite crystals at random, to produce a tunable optoelectronic device.
In the use of photodetectors usually, must be coupled to a filter to increase the signal to noise ratio due to the interference with the various background noise. In general, perovskite polycrystalline thin film photodetector does not have the function of filtering.
To get the narrowband photodetection, it is necessary to use a filter or use the materials which have narrowband absorption, but this usually encounters the problems such as expensive, difficult to design the optical system or the filter lens is susceptible to dust and other pollution. Bulk single crystal perovskite photodetector can effectively solve the above problems.
In this paper, it is found that the maximum values of on/off ratio will move along with the absorption edge so that a tunable narrowband photodetector can be obtained by the ion exchange.

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