本論文的目的為針對近年來熱門的二維材料（例如石墨烯、二硫化鉬及二硒化鎢）的光伏特性進行系統性的研究，並與目前商用材料（例如矽）結合來製作元件，以增加未來在半導體及能源產業量產的機會。

論文主題針對二維材料包括二硫化鉬/矽的異質接面、混合型太陽能電池摻雜石墨烯量子點及二硫化鉬/二硒化鎢單層側向異質接面進行材料鑑定與光伏元件製程，為發展下一世代的奈米能源提供相關應用。

我們成功利用大面積單層二硫化鉬及p型矽製作第二型的異質接面光伏元件。其中單層二硫化鉬和p型矽在界面之間形成內建電場，可用來幫助光激發的載子有效分離，並達到5.23%的能量轉換效率。接著我們將石墨烯量子點混於PEDOT:PSS之中，有效利用石墨烯光子降轉換和增加導電度的特性，在矽/PEDOT:PSS混合型太陽能電池達到13.22%的效率。其中短路電流和填充因子分別從32.11提升到36.26 mA/cm2以及從62.85%提升到63.87%。最後我們研究二硒化鎢/二硫化鉬單層側向p-n異質接面並製作成元件。此元件達到0.26 A/W的光響應並具有很好的全方向性光偵測功能。此異質接面所形成的二極體理想因子可達1.25，並具有明顯的閘極控制功能。另外此元件展現快速響應、弱光偵測及高溫操作能力。

The aim of this thesis is to provide systematic exploration of the photovoltaic characteristics in most popular 2D materials (graphene, MoS2, and WSe2) in recent years for designing devices compatible with conventional materials (such as Si) to expand the opportunity for mass production in the future semiconductor and energy industries.

In this thesis, the fabrication and characterization of 2D material based photovoltaic devices including MoS2/Si heterojunction, graphene quantum dot in hybrid solar cells, and MoS2/WSe2 lateral heterojunction have been achieved for developing the nanoscale energy applications for the next generation.

We realized photovoltaic operation in large-scale MoS2 monolayers by the formation of a type-II heterojunction with p-Si. The MoS2 monolayer introduces a built-in electric field near the interface between MoS2 and p-Si to help photo-generated carrier separation. Such a heterojunction photovoltaic device achieves a power conversion efficiency of 5.23%.

By employing graphene quantum dots in PEDOT:PSS, we have accomplished the efficiency of 13.22% in Si/PEDOT:PSS hybrid solar cells. The efficiency enhancement is based on concurrent improvement in optical and electrical properties by the photon downconversion process and the improved conductivity of PEDOT:PSS. The short circuit current and the fill factor are increased from 32.11 to 36.26 mA/cm2 and 62.85% to 63.87%, respectively.

Finally, electrical and optical properties of lateral monolayer WSe2-MoS2 p-n heterojunction were characterized to demonstrate a high responsivity of 0.26 A/W with excellent omnidirectional photodetection capability. The heterojunction functioning as a diode exhibits prominent gate-tuning behavior with an ideality factor of 1.25. In addition, ultrafast photoresponse, low-light detectability, and high-temperature operation have been achieved.

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