化學(xué)氣相淀積石墨烯在不同襯底上的表征以及多層石墨烯在有機(jī)太陽(yáng)能電池中的應(yīng)用
發(fā)布時(shí)間：2018-08-15 11:47
【摘要】：由于石墨烯具有不同尋常的物理性質(zhì)，它的發(fā)現(xiàn)引發(fā)了物理學(xué)界的廣泛關(guān)注。這種特殊的二維材料已被用于各種量子實(shí)驗(yàn)。不僅如此，石墨烯還具有獨(dú)特的機(jī)械、光學(xué)、電學(xué)性質(zhì)，使得石墨烯可以被用來(lái)制作各類新型器件。在室溫下，石墨烯的電子遷移率高達(dá)200000cm2/V·s。如此高的載流子遷移率使得石墨烯有希望被用來(lái)制作高頻高速晶體管。除此以外，石墨烯還有可能在其他方面得到應(yīng)用，比如微機(jī)電系統(tǒng)MEMS、電池以及各類探測(cè)器。 均勻大面積的石墨烯材料是確保石墨烯器件的高性能和推進(jìn)該器件走向應(yīng)用的關(guān)鍵。在目前的石墨烯制備方法中，化學(xué)氣相沉積（CVD）法被認(rèn)為是制備均勻大面積石墨烯的最佳制備方法之一。在CVD法制備石墨烯時(shí)，已經(jīng)有多種不同的金屬被用來(lái)作襯底，如銅、鎳等。得益于銅箔表面的自限制作用，銅箔襯底上可以生長(zhǎng)出大面積的單層石墨烯，因此銅箔已經(jīng)成為CVD法制備石墨烯的最常用襯底。為了盡量增大石墨烯單晶的晶疇面積，本文提出電化學(xué)拋光的方法對(duì)銅箔進(jìn)行預(yù)處理。實(shí)驗(yàn)結(jié)果表明，經(jīng)過(guò)電化學(xué)拋光處理后的銅箔表面更加光亮干凈，這有利于降低石墨烯的成核密度。 為了制作石墨烯器件，生長(zhǎng)結(jié)束后需要進(jìn)行石墨烯轉(zhuǎn)移。然而，在此轉(zhuǎn)移過(guò)程中石墨烯容易受到有機(jī)物的污染。光刻膠雜質(zhì)是測(cè)量石墨烯本征物理性質(zhì)和制作石墨烯器件的障礙。為了去除石墨烯表面的有機(jī)物殘留，通常在高溫下對(duì)石墨烯進(jìn)行退火。研究表明高溫退火確實(shí)可以有效的去除光刻膠殘留，可是高溫退火對(duì)石墨烯本身的物理性質(zhì)影響并沒有深入的研究。本文把CVD制備的石墨烯轉(zhuǎn)移到藍(lán)寶石襯底上并且將其在不同的溫度進(jìn)行退火實(shí)驗(yàn)。利用AFM、拉曼光譜表征等手段，探究了高溫退火工藝與襯底間殘余應(yīng)力的關(guān)系。通過(guò)分析Raman光譜，研究了石墨烯上殘余應(yīng)力的積累。并且在實(shí)驗(yàn)的基礎(chǔ)上，本文進(jìn)一步建立了退火殘余應(yīng)力的應(yīng)力積累模型，獲得是應(yīng)力積累系數(shù)為0.35，由此模型導(dǎo)出的應(yīng)力殘余系數(shù)與實(shí)驗(yàn)結(jié)果取得了很好的吻合。 銦錫氧化物ITO常用于制作有機(jī)太陽(yáng)能電池的電極，然而其高昂的價(jià)格制約著太陽(yáng)能電池的普及。不僅如此，銦錫氧化物十分易碎，，而且對(duì)酸十分敏感，使得可靠性下降。銦錫氧化物中本身化學(xué)性質(zhì)較活潑，其中的離子容易滲入太陽(yáng)能電池的有效層，造成有機(jī)太陽(yáng)能電池性能下降，因此尋找到ITO的替代材料很有意義。石墨烯具有很高的透光率，單層石墨烯透光率高達(dá)97.7%，折射率小于0.1%，幾乎可以忽略。雖然具有很高的透光率，但是未經(jīng)摻雜的單層石墨烯方阻太高，不適合制作透明電極，而隨著層數(shù)的增加，石墨烯的方阻會(huì)逐漸降低。所以為了制作透明電極，本文研究了疊層石墨烯轉(zhuǎn)移工藝。 這里提出了一種免于退火的疊層石墨烯轉(zhuǎn)移方法，利用這種方法轉(zhuǎn)移獲得的疊層石墨烯同時(shí)具有較高的透光率和電導(dǎo)率。Raman測(cè)試表明，盡管隨著疊層層數(shù)的增加，轉(zhuǎn)移步驟增多，但是疊層轉(zhuǎn)移工藝并沒有破壞石墨烯以及引入非故意摻雜。實(shí)驗(yàn)獲得是4層石墨烯電極的透光率超過(guò)86%，方阻小于100。本文在此基礎(chǔ)上進(jìn)一步制作了有機(jī)太陽(yáng)能電池，得到的開路電壓為0.62V，短路電流密度為0.51mA/cm2。證明這種轉(zhuǎn)移工藝制備的疊層石墨烯電極，有潛力在有機(jī)太陽(yáng)能電池中用來(lái)替代ITO。 總之，本文主要在石墨烯生長(zhǎng)、石墨烯與襯底間的相互作用、退火工藝在石墨烯中引入的殘余應(yīng)力、以及疊層石墨烯電極的制備和應(yīng)用等方面進(jìn)行了探索研究。
[Abstract]:Graphene has attracted much attention in the field of physics because of its unusual physical properties. This special two-dimensional material has been used in various quantum experiments. Moreover, graphene has unique mechanical, optical and electrical properties, making it possible to fabricate various new devices at room temperature. The electron mobility of the olefin is as high as 200,000 cm 2/V.s. Such high carrier mobility makes it possible for graphene to be used in high-frequency and high-speed transistors.
The uniform large area graphene material is the key to ensure the high performance of graphene devices and to promote the application of graphene devices.Chemical vapor deposition (CVD) is considered as one of the best methods to prepare uniform large area graphene in current graphene preparation methods. Due to the self-limiting effect of copper foil surface, a large area of monolayer graphene can be grown on copper foil substrate. Therefore, copper foil has become the most commonly used substrate for preparing graphene by CVD method. The results show that the surface of copper foil treated by electrochemical polishing is brighter and cleaner, which is beneficial to reducing the nucleation density of graphene.
In order to fabricate graphene devices, it is necessary to transfer graphene after growth. However, graphene is susceptible to organic contamination during this process. Impurities in photoresist are obstacles in measuring the intrinsic physical properties of graphene and in fabricating graphene devices. In this paper, graphene prepared by CVD was transferred to sapphire substrate and annealed at different temperatures. Characterized by AFM, Raman spectroscopy. The relationship between the high temperature annealing process and the residual stress between the substrates was investigated by means of the Raman spectroscopy. The accumulation of residual stress on graphene was studied by analyzing the Raman spectra. The coefficients agree well with the experimental results.
Indium tin oxide ITO is often used to make electrodes for organic solar cells. However, its high price restricts the popularity of solar cells. Moreover, indium tin oxide is very fragile and sensitive to acid, which makes it less reliable. Graphene has a very high transmittance. The transmittance of single-layer graphene is as high as 97.7%, and the refractive index is less than 0.1%. It is almost negligible. Although it has a very high transmittance, the undoped single-layer graphene has too high square resistance and is not suitable for use. As the number of layers increases, the square resistance of graphene decreases gradually.
In this paper, an annealing-free laminated graphene transfer method is proposed. The laminated graphene obtained by this method has high transmittance and conductivity at the same time. Raman test shows that although the transfer steps increase with the increase of the number of layers, the laminated graphene transfer process does not destroy the graphene and the introduction of unintentional doping. The experimental results show that the light transmittance of the four-layer graphene electrode is more than 86% and the square resistance is less than 100. Based on this, an organic solar cell is fabricated. The open-circuit voltage is 0.62V and the short-circuit current density is 0.51mA/cm2. Generation ITO.
In summary, the growth of graphene, the interaction between graphene and substrate, the residual stress induced by annealing process in graphene, and the preparation and application of laminated graphene electrode were studied in this paper.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN304.055;TM914.4
[Abstract]:Graphene has attracted much attention in the field of physics because of its unusual physical properties. This special two-dimensional material has been used in various quantum experiments. Moreover, graphene has unique mechanical, optical and electrical properties, making it possible to fabricate various new devices at room temperature. The electron mobility of the olefin is as high as 200,000 cm 2/V.s. Such high carrier mobility makes it possible for graphene to be used in high-frequency and high-speed transistors.
The uniform large area graphene material is the key to ensure the high performance of graphene devices and to promote the application of graphene devices.Chemical vapor deposition (CVD) is considered as one of the best methods to prepare uniform large area graphene in current graphene preparation methods. Due to the self-limiting effect of copper foil surface, a large area of monolayer graphene can be grown on copper foil substrate. Therefore, copper foil has become the most commonly used substrate for preparing graphene by CVD method. The results show that the surface of copper foil treated by electrochemical polishing is brighter and cleaner, which is beneficial to reducing the nucleation density of graphene.
In order to fabricate graphene devices, it is necessary to transfer graphene after growth. However, graphene is susceptible to organic contamination during this process. Impurities in photoresist are obstacles in measuring the intrinsic physical properties of graphene and in fabricating graphene devices. In this paper, graphene prepared by CVD was transferred to sapphire substrate and annealed at different temperatures. Characterized by AFM, Raman spectroscopy. The relationship between the high temperature annealing process and the residual stress between the substrates was investigated by means of the Raman spectroscopy. The accumulation of residual stress on graphene was studied by analyzing the Raman spectra. The coefficients agree well with the experimental results.
Indium tin oxide ITO is often used to make electrodes for organic solar cells. However, its high price restricts the popularity of solar cells. Moreover, indium tin oxide is very fragile and sensitive to acid, which makes it less reliable. Graphene has a very high transmittance. The transmittance of single-layer graphene is as high as 97.7%, and the refractive index is less than 0.1%. It is almost negligible. Although it has a very high transmittance, the undoped single-layer graphene has too high square resistance and is not suitable for use. As the number of layers increases, the square resistance of graphene decreases gradually.
In this paper, an annealing-free laminated graphene transfer method is proposed. The laminated graphene obtained by this method has high transmittance and conductivity at the same time. Raman test shows that although the transfer steps increase with the increase of the number of layers, the laminated graphene transfer process does not destroy the graphene and the introduction of unintentional doping. The experimental results show that the light transmittance of the four-layer graphene electrode is more than 86% and the square resistance is less than 100. Based on this, an organic solar cell is fabricated. The open-circuit voltage is 0.62V and the short-circuit current density is 0.51mA/cm2. Generation ITO.
In summary, the growth of graphene, the interaction between graphene and substrate, the residual stress induced by annealing process in graphene, and the preparation and application of laminated graphene electrode were studied in this paper.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN304.055;TM914.4
【共引文獻(xiàn)】
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