全無機鈣鈦礦（All-inorganic Pervoskite）晶體材料不僅具備相當優異的光吸收係數、電子遷移率、色純度以及可調式發光波長的光電特性之外，其可溶液製備更是促使鈣鈦礦材料在太陽能電池、量子點以及發光二極體等應用上具有極大發展潛力的優勢之一。
本研究首次提出「水溶液法（Water-based Process）」，在室溫下以“水”為溶劑，藉由調整系統內CsBr及Pb(NO3)2莫耳濃度製備出CsxPbyBrz鈣鈦礦系之粉末。並以XRD、SEM以及EDS分析其晶體結構以及合成機制，再佐以UV-Vis、UPS及PL分析各粉末的光學性質。綜合其結果顯示，在CsBr不足的情況之下，可合成出間接能隙為3.1eV且光致發光為紫光及橘光之二維板狀CsPb2Br5粉末；而隨著CsBr濃度逐漸提升，則會形成CsPb2Br5及CsPbBr3兩相共存之過渡帶，其表面會具有奈米級CsPbBr3量子侷限效應的綠光產生；而當CsBr為富有相時，即可合成出高品質、直接能隙為2.3eV之三維單斜CsPbBr3粉末。
最後，本研究不僅通過改變CsX鹵素原子製備出多種鈣鈦礦粉末之外，亦選取最低成本且高品質的CsPbBr3鈣鈦礦粉末，以製備太陽能電池、發光二極體及可撓式發光元件為目標，成功將粉末應用於單源熱蒸鍍及噴霧法等多種薄膜製程當中，不僅可以有效地改善傳統製程中有機溶劑對環境的汙染，亦可避免高沸點油性配體對商業應用上所造成之限制，達到低成本、大面積、高產率且環保無汙染等訴求，展現出水溶液法製備鈣鈦礦之技術無限的發展潛力。

In this study, we report for the first time the synthesized of perovskite powder by “ water-based process ”. It is not only quite simple at room temperature, but also through the "water" as a solvent without any high boiling organic solvents and ligands, achieving low-cost, large-area, mass production and environmentally friendly.
CsxPbyBrz powder was obtained by systematically varying the molar ratios of CsBr/Pb(NO3)2 in the deionized water. We used the XRD, SEM and EDS to evaluate the powders CsxPbyBrz crystal structural and chemical composition. Therefore, we combined our experimental observations found that the chemical reaction mechanism is related to “ Solubility equilibrium ” , so that CsBr in the system can reach the saturated state, thereby inhibiting the degradation reaction of CsPbBr3 in water.
In addition, we also use the UV-Vis, UPS and PL spectrum to analysis the optical and electrical properties. The results show that with the increase of CsBr concentration, the influence is gradually changed from indirect energy gap 3.1eV CsPb2Br5 to direct energy gap 2.3eV CsPbBr3. Moreover, the crystal growth mechanism for the water-based process was investigated by TEM analysis.
Finally, our research team successfully applied this powder to single-source evaporation and spray-coated technique, and also prepared various perovskite powders by changing the halogen atoms of CsX, demonstrating the unlimited development potential of this water-based process synthesized perovskite technology.

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