元件結構

第三章實驗內容與結果分析

3.4 元件結構

本文的 LEC 元件皆是如三明治一般將發光層用陰、陽電極夾於中心的結構，且為下發光元件的形式，當發光層被驅動後光會朝四面八方發射，

而金屬陰極會將光反射至朝下；本文內的白光 LEC 元件的各層結構如下表示： ITO/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) (30 nm)/發光層(200 nm)/鋁(100 nm)

其示意圖如下圖 17 所示：

圖 17、元件結構示意圖

1. 陰極(Al Cathode)：一般有機元件為了能使電子有效的注入發光層的最

3.5 材料介紹及其光物理特性 物，其中的 dfppz 為 1-(2,4-difluorophenyl)pyrazole 而 dtb-bpy 為 [4,4′-di(tert-butyl)-2,2′-bipyridine]，此材料於先前的文獻 Tamayo 等人做為主體材料而被發表[29]。

2. 2 號錯合物[Ir(ppy)2(biq)]⁺(PF6─

)為發紅光的錯合物，其中的 ppy 為 2-phenylpyridine 而 biq 為 2,2′-biquinoline，此材料於 Su 等人的白光 LEC 文獻被作為發紅光的客體材料[41]。

3. 3 號錯合物[Ir(ppy)₂(dasb)]⁺(PF₆^─)為發橘光的高效率錯合物，其中的 dasb 為 4,5-diaza-9,9’-spirobifluorene，此材料在文獻中作為主客體 LEC 元件的客體材料，因其可調整白光 LEC 內的載子平衡而提升元件效率，

使元件外部量子效率大於 10%[37]。

4. BMIM⁺(PF6

─)其中的 BMIM 為 1-butyl-3-methylimidazolium 而 PF6為 hexafluorophosphate，材料的結構式如圖 18 所示；此材料為一種黏稠、

無色且不溶於水的離子性液體，其可為 LEC 元件提供額外離子以幫助傳輸。

5. PEDOT:PSS 為高分子聚合物且導電率極高的水溶液，可根據不同的調配方式得到導電率不同之水溶液。該產品是由 PEDOT 和 PSS 兩種物質構成，PEDOT 是 EDOT（3,4-ethylenedioxylthiophene）的聚合物，

而 PSS 為 poly(styrenesulfonate)。

前三種錯合物於薄膜態及溶於溶劑(10^-5 M 的二氯甲烷)的光物理特性

摻雜在白光 LEC 作為發紅光的客體材料[41]；3 號錯合物的橘色光激發光的濃度(0.05 wt.%)相較於單一摻雜薄膜的紅光客體濃度(0.2 wt.%)要低，但藉由雙重摻雜薄膜中的發橘光客體提供了部份光激發光的紅光，因而提升

圖 18、分子結構式分別為 1 號錯合物[Ir(dfppz)₂(dtb-bpy)]⁺(PF6

圖 19、離子性溶液 BMIM⁺(PF6─

)之結構式

圖 20、PEDOT:PSS 之結構式

表 2、本文內的錯合物光物理特性整理

Complex

λmax, PL (nm)^a, Φ^b

Solution^c Neat film or host-guest film Film with BMIM⁺(PF6─

)^d

1 492, 1.00 492, 0.75 －

2 656, 0.20 672, 0.09 －

3 558, 0.52 593, 0.32 －

2 (0.2 wt.%) : 1 － (487, 600), 0.61 (485, 598), 0.64

2 (0.05 wt.%) and 3 (0.1 wt.%): 1

－ (506, 592), 0.64 (505, 592), 0.69

a光激發光頻譜峰值的波長數值。 ^b光激發光的量子產率。 ^c材料在溶於二氯甲烷(10^-5 M) 的情況下。^d薄膜內除了主要材料外含有 20 wt.%的 BMIM⁺(PF₆^─)鹽類情況下。

圖 21、1 號、2 號和 3 號錯合物溶於二氯甲烷(10^-5M)與純膜的光激發光頻譜

400 500 600 700 800 900 0.0

0.2 0.4 0.6 0.8 1.0

1.2

^{1, Sol.} ^{2, Sol.} ^{3, Sol.}

1, Film 2, Film 3, Film

PL Int ensit y (a.u .)

Wavelength (nm)

圖 22、為以下四種情況製成薄膜的光激發光頻譜：單一摻雜[2 號(0.2 wt.%)]

和雙重摻雜[2 號(0.05 wt.%)與 3 號(0.1 wt.%)] 分別加入主體 1 號錯合物並且再區分是否有摻入離子性溶液 BMIM⁺(PF6─

) (20 wt.%)

400 500 600 700 800

0.0 0.5 1.0 1.5 2.0 2.5

3.0

Without BMIM⁺PF₆

Single doping Double doping With BMIM⁺PF₆

Single doping Double doping

PL Int ensit y (a.u .)

Wavelength (nm)

3.6 元件電激發光分析 標(0.328, 0.423)和(0.318, 0.427)，再者對固態照明極為重要的演色性係數 (CRI)而言，兩種元件在 3.1 伏特到 3.3 伏特間的演色性係數都可以維持在

當電流密度漸增且載子注入越多的情況下，載子就越容易能填入較高的 3 伏特的(1.7 %、1.7 cd/A、1.9 lm/W)、3.0 伏特的(3.2 %、5.4 cd/A、5.4 lm/W) 和 3.1 伏特的(3.2 %、6.2 cd/A、5.9 lm/W)，而元件二的情況分別為 2.9 伏特的(5.6 %、9.2 cd/A、10.0 lm/W)、3.0 伏特的(7.4 %、14.8 cd/A、15.0 lm/W) 和 3.1 伏特的(6.3 %、13.4 cd/A、12.8 lm/W)，其單一摻雜元件 I 的效率就和先前離子過渡金屬錯合物為基準的單一摻雜白光 LEC 約略相同，而雙重摻雜元件 II 的效率卻高於單一摻雜元件 I 的兩倍多，且比現有文獻發表的白光 LEC 還要高[14][15][41][47][51]，由於雙重摻雜薄膜和單一摻雜薄膜的光激發光效率相差不是很大，但在元件發光效率卻有極大的差距，此種效率增益證實了 3 號錯合物的摻雜使載子濃度獲得更好的平衡，況且摻雜區間靠近 LEC 元件兩側的電極也確保了載子注入的平衡[6]~[56]。

單一摻雜薄膜內 1 號主體材料和 2 號客體材料的最低已填滿軌域 (LUMO)相差 0.46 電子伏特，而兩個材料間的最高未填滿軌域(HOMO)則相差了 0.39 電子伏特，其中最低已填滿軌域能階落差大於最高未填滿軌域的能階差，此結果造成電子比電洞容易被捕捉，而電洞較電子容易在能

階上傳輸；相較於單一摻雜薄膜而言，雙重摻雜薄膜內的 2 號客體材料與

種白光 LEC 在 2.9 伏特驅動下皆顯示低弱的外部量子效率，為了使離子過渡金屬錯合物為材料的白光 LEC 元件能達到更好的生命期，其元件毀損的機制細節仍然有待釐清和更詳細的研究。

表 3、白光 LEC 的電激發光特性整理

a 元件結構為 ITO/PEDOT:PSS (30 nm)/emissive layer (200 nm)/Al (100 nm)，其中元件 I 的發 光層內含 1 (79.8 wt.%)、 2 (0.2 wt.%)和 BMIM⁺(PF₆^─) (20 wt.%)，而元件 II 的發光層內含 1

圖 23、(a)元件 I 在不同驅動電壓下的電激發光頻譜分別與其發光層之光激發光頻譜的比較圖

400 500 600 700 800

0.0 0.5 1.0 1.5 2.0 2.5 3.0 (a)

EL 3.3 V EL 3.1 V EL 2.9 V

Int ensity (a.u.)

Wavelength (nm)

圖 24、(b)元件 II 在不同驅動電壓下的電激發光頻譜分別與其發光層之光激發光頻譜的比較圖

400 500 600 700 800

0.0 0.5 1.0 1.5 2.0 2.5 3.0 (b)

EL 3.3 V EL 3.1 V EL 2.9 V

Int ensit y (a.u .)

Wavelength (nm)

圖 25、主體材料 1 號以及客體材料 2 號與 3 號的分子能階對照圖

圖 26、雙重摻雜元件在 3.3V 驅動下的 CIE 變化圖

0.0 0.2 0.4 0.6 0.8 0.0

0.2 0.4 0.6 0.8

Saturation

CIE1931 NTSC

Host and two guests

y

x

圖 27、雙重摻雜元件在 3.1V 驅動下的 CIE 變化圖

0.0 0.2 0.4 0.6 0.8 0.0

0.2 0.4 0.6 0.8

Saturation

CIE1931 NTSC

Host and two guests

y

x

圖 28、單一摻雜元件在 3.3V 驅動下的 CIE 變化圖

0.0 0.2 0.4 0.6 0.8 0.0

0.2 0.4 0.6 0.8

Saturation

CIE1931 NTSC

Host and two guests

y

x

圖 29、單一摻雜元件在 3.1V 驅動下的 CIE 變化圖

0.0 0.2 0.4 0.6 0.8 0.0

0.2 0.4 0.6 0.8

Saturation

CIE1931 NTSC

Host and two guests

y

x

圖 30、(a)元件 I 在固動驅動電壓 2.9、3.1 和 3.3 伏特下的亮度(實心符號) 及電流密度(空心符號)對時間的變化圖

0 100 200 300 400 500 600 0

2 4 6

10

^-4

10

^-3

10

^-2

10

^-1

(a)

2.9 V 3.1 V 3.3 V

Bright ness ( cd/m

)

Time (min)

Current Densit y (m A /cm

)

圖 31、(b)元件 II 在固動驅動電壓 2.9、3.1 和 3.3 伏特下的亮度(實心符號) 及電流密度(空心符號)對時間的變化圖

0 100 200 300 400 500 600 0

5 10 15 20

10

^-4

10

^-3

10

^-2

10

^-1

(b)

2.9 V 3.1 V 3.3 V

Bright ness (cd /m

)

Time (min)

Current Den sity (m A /cm

)

圖 32、(a)元件 I 在固動驅動電壓 2.9、3.1 和 3.3 伏特下的外部量子效率(實心符號)及能量效率(空心符號)對時間的變化圖

0 100 200 300 400 500 600 0

1 2 3 4

0 2 4 6 (a)

2.9 V 3.1 V 3.3 V

External Q uan tu m Eff iciency (% )

Time (min)

Pow er E ff iciency (lm /W )

圖 33、(b)元件 II 在固動驅動電壓 2.9、3.1 和 3.3 伏特下的外部量子效率(實心符號)及能量效率(空心符號)對時間的變化圖

0 100 200 300 400 500 600 0

2 4 6 8 10

0 5 10 15 (b)

2.9 V 3.1 V 3.3 V

External Q uan tu m Eff iciency (% )

Time (min)

Pow er E ff iciency (lm /W )

圖 34、(a)元件 I(空心符號)和元件 II(實心符號)與固動驅動電壓 2.9、3.1

Bias Voltage (V)

Brightness

圖 35、(b)元件 I(空心符號)和元件 II(實心符號)與固動驅動電壓 2.9、3.1 和 3.3 伏特相依下的最大外部量子效率(圓形符號)與生命期(三角形符號) 的變化圖

2.9 3.0 3.1 3.2 3.3

2 4 6 8

0 300 600 900 1200 1500

External Q uan tu m Eff iciency (% )

Bias Voltage (V) EQE Device

I II

Lifetime (b)

Lif etim e (m in)

第四章結論

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在文檔中高效率雙重摻雜固態白光電化學元件 (頁 31-0)

第三章 實驗內容與結果分析

3.4 元件結構

400 500 600 700 800 900 0.0

0.2 0.4 0.6 0.8 1.0

1.2

PL Int ensit y (a.u .)

Wavelength (nm)

400 500 600 700 800

0.0 0.5 1.0 1.5 2.0 2.5

3.0

PL Int ensit y (a.u .)

Wavelength (nm)

Int ensity (a.u.)

400 500 600 700 800

0.0 0.5 1.0 1.5 2.0 2.5 3.0 (b)

Int ensit y (a.u .)

Wavelength (nm)

0.0 0.2 0.4 0.6 0.8 0.0

0.2 0.4 0.6 0.8

y

x

0.0 0.2 0.4 0.6 0.8 0.0

0.2 0.4 0.6 0.8

y

x

0.0 0.2 0.4 0.6 0.8 0.0

0.2 0.4 0.6 0.8

y

x

0.0 0.2 0.4 0.6 0.8 0.0

0.2 0.4 0.6 0.8

y

x

0 100 200 300 400 500 600 0

2 4 6

10

10

10

10

(a)

Bright ness ( cd/m

)

Time (min)

Current Densit y (m A /cm

)

0 100 200 300 400 500 600 0

5 10 15 20

10

10

10

10

(b)

Bright ness (cd /m

)

Time (min)

Current Den sity (m A /cm

)

0 100 200 300 400 500 600 0

1 2 3 4

0 2 4 6 (a)

External Q uan tu m Eff iciency (% )

Time (min)

Pow er E ff iciency (lm /W )

0 100 200 300 400 500 600 0

2 4 6 8 10

0 5 10 15 (b)

External Q uan tu m Eff iciency (% )

Time (min)

Pow er E ff iciency (lm /W )

Bias Voltage (V)

Brightness

2.9 3.0 3.1 3.2 3.3

2 4 6 8

0 300 600 900 1200 1500

External Q uan tu m Eff iciency (% )

Bias Voltage (V) EQE Device

I II

Lifetime (b)

Lif etim e (m in)

第三章實驗內容與結果分析

第四章結論