軟性有機發光二極體顯示器(Flexible organic light emitting diode display)為下一個時代的顯示器的明日之星，但是其對水氣及氧氣極度敏感，因此封裝是一個不可忽略且極度重要的課題。水氣穿透率(單位: g/m2/day)的大小用來評估封裝有機發光二極體的品質，而估計封裝有機發光二極體其水氣穿透率最小為10-6 g/m2/day，目前普遍的量測方法都有長量測時間或是不可重覆使用的問題。近年來，石墨烯被發現是一個優良的氣體感測器，具備反應時間迅速及靈敏的性質，其原理在於氣體分子接觸石墨烯時會有電荷轉移之效應(Charge transfer effect)。故本研究應用石墨烯元件於水氣穿透率的量測，使用化學氣相沉積法(Chemical vapor deposition)成長石墨烯，並使用遮罩鍍製電極。固定偏壓為1伏特觀察元件電流藉由電荷轉移改變做為量測，接著運用理論及邏輯推演的模型擬合，跟實驗的曲線近乎吻合，且量測時間比目前普遍的量測方法還要少許多。相信未來可以成功以石墨烯量測法做為一個新、快速且準確的量測封裝有機發光二極體之水氣穿透率的方法。本研究以電阻平均2 ~2.5千歐姆的石墨烯元件，在量測環境35 ± 3℃ 相對濕度99.9 %下，量測出水氣穿透率5 x 10-4 g/m2/day的樣品，其石墨烯元件電流變化率有72 %變化，其量測時間約一小時。;Flexible organic light emitting diode display is a candidate for next generation display device but the water vapor and oxygen is easy to damage the organic element. Therefore, the organic element needs barrier film to protect it. Water vapor transmission rate (WVTR, unit: g/m2/day)is used to evaluate the quality for encapsulation of organic element, which is estimated 10-6 g/m2/day There are two main ways to measure the WVTR for encapsulation of organic element but they have some disadvantages like that long time measurement and non-reusable. Recently, graphene is found to be a good gas sensor. Graphene has fast response time and sensitive characteristics. The charge transfer between the molecules and the graphene surface when the molecules absorb on graphene is in seconds. In this study, we made a fast WVTR-measurement system by graphene-based device. The graphene-based device is prepared by transferred the graphene which is grown by chemical vapor deposition (CVD) on glass subtrate first and then deposited the metal electrode with mask. The source voltage of graphene-based device kept 1V. Calculating the change of device current due to charge transfer between the molecules and the graphene surface that can be converted to how many water molecules absorb on graphene. Using physically model to fit the measurement data, and the fitting is very similar to experiment results. In the future, the graphene-based device measurement can be a new, fast and accurate way to measure WVTR. In this studt, we use a graphene-based device with average resistance about 2 ~ 2.5 kohm to measure a sample with WVTR ~ 5 x 10-4 g/m2/day under test conition: temperatue 35 ± 3 ℃, relative humidity 85 % in about one hour. The current change rate at the device is 72 %.
