利用不對稱類鹵素分子形成之二維鈣鈦礦結合二維材料之高響應混合型光偵測器

Abstract

本文主要探究以不對稱之類鹵素分子來取代鈣鈦礦中的X位陰離子，以達成分裂三維鈣鈦礦，並讓其成為二維鈣鈦礦，再藉由二維鈣鈦礦有遠優於其三維時的特性，將其與二硫化鉬結合，形成具有極高光響應率之混合型光偵測器。 內容大致上分為本文所使用之二維鈣鈦礦特性之探討，首先我們將原本用於鈣鈦礦X位的陰離子從鹵素原子換為不對稱類鹵素分子SCN，由於其不對稱的特性，將會導致鈣鈦礦X位失去了連結鈣鈦礦上下層的能力，以造成鈣鈦礦從三維分裂為二維，並對其之物理特性進行探討。第二步則是將二維鈣鈦礦塗佈於二硫化鉬之上，並觀察兩者之間能帶關係所造成的電子轉移，以及二維鈣鈦礦對於二硫化鉬之中的硫空缺進行填補。第三步，將會對此混合型光偵測器進行光電特性上之量測，並觀察到其有相較於過往期刊中鈣鈦礦與二硫化鉬結合之光偵測器有更高的光響應率，並且也有不差的反應時間。最後一步，我們會著重於此元件之穩定性，相較於傳統鈣鈦礦非常差的水、氧耐性，此元件能長期保存於真空中而不劣化，在大氣下也能保存上許多天而不致水解。 而本二硫化鉬/鈣鈦光混合型光偵測器，擁有非常高之光響應率，最大值可在0.5伏特之外加偏壓下達到1.22 x 105 A/W，遠遠高於多數期刊論文中所紀錄之二硫化鉬/鈣鈦礦混合型光偵測器之光響應率。而反應時間中的上升時間，也只需要0.16秒，相較於純二硫化鉬的121.1秒，大大的縮減到了可以於生活中應用的程度。最後該元件在保存了一個月之後，光響應率亦沒有明顯的下降，由此可見該元件可觀之穩定性。

In this article, we use asymmetric pseudo halide instead of the X-site anion in perovskites to change perovskite from 3D to 2D. Moreover, combining this 2D perovskite and MoS¬2, we can make a hybrid photodetector with high responsivity. First of all, we change the X-site anion in perovskite to an asymmetric pseudo halide anion SCN-. Because of the asymmetric trait, the X-site of the perovskite will lose its ability for connecting layers. We will investigate the physical characteristics of this 2D perovskite in first part. Secondly, the 2D perovskite was spin-coated on MoS2. After that, we focus on the charge transfer phenomenon by the relative band structure between these two material and the sulfur vacancies passivation. Moreover, the performance of this hybrid photodetector shows high responsivity and fast response time. At last, compared with 3D perovsites, this SCN-based 2D perovskite has exceptional stability. It is able to stay stable few days in ambient air. This hybrid photodetector has high responsivity, 1.22 x 105 A/W, by 0.5 V bias voltage, and this performance is higher than the records of perovskite/ MoS2 ¬¬hybrid photodetectors. At the same time, the rise time is also 0.16 s which is an extremely decrease compared with 121.1 s the rise time of pristine MoS2. Furthermore, the responsivity of this device had not obviously degraded more than one month. This indicates the great stability of this device.