氫化微晶硅鍺薄膜的微結(jié)構(gòu)及光電特性的研究與優(yōu)化
發(fā)布時(shí)間：2018-07-29 20:25
【摘要】：硅基薄膜太陽電池由于低成本等潛在優(yōu)勢,日益引起人們的重視并得到了迅速的發(fā)展。疊層太陽電池可有效提高硅基薄膜電池的轉(zhuǎn)換效率和穩(wěn)定性,成為目前硅薄膜研究領(lǐng)域的熱點(diǎn)問題。氫化微晶硅鍺薄膜(μc-Si1-xGex：H)由于具有窄帶隙、帶隙可調(diào)、高吸收系數(shù)等優(yōu)點(diǎn),是疊層電池中底電池有源層材料的理想選擇之一,有著廣闊的應(yīng)用前景。 但μc-Si1-xGcx:H薄膜中存在復(fù)雜的混合相結(jié)構(gòu)(非晶相、晶相、晶界和空洞)及各種合金組態(tài)的化學(xué)鍵(Si-Si、Si-Ge、Ge-Ge和(Si(Ge)-Hn)n等),為薄膜結(jié)構(gòu)的分析和性能的優(yōu)化帶來一定的困難。為了獲得不同Ge含量下μc-Si1-xGex:H薄膜的微結(jié)構(gòu)及結(jié)構(gòu)與光電性能的關(guān)系,本論文采用RF-PECVD技術(shù),從薄膜微結(jié)構(gòu)的角度出發(fā),對μc-Si1-xGex:H薄膜的電學(xué)特性和光吸收性質(zhì)進(jìn)行了系統(tǒng)研究。主要研究內(nèi)容和成果如下： 首先,我們從Ge含量(0～100%)和晶化率(Si-Ge,Si-Ge,Ge-Ge)這兩個(gè)結(jié)構(gòu)參數(shù)出發(fā),系統(tǒng)地研究了不同Ge含量下,μc-Si1-xGcx:H薄膜的微結(jié)構(gòu)及其對薄膜電學(xué)性質(zhì)的影響。研究發(fā)現(xiàn)： 1)Ge含量小于60%時(shí),與Ge相關(guān)的成鍵(Si-Ge和Ge-Ge)較易處于非晶網(wǎng)格中,薄膜的晶化率取決于Si-Si鍵的有序程度(XSi-Si)和Ge含量。通過對不同條件下制備的微晶硅鍺薄膜的測試分析發(fā)現(xiàn),Ge含量以及薄膜的晶化率的變化對薄膜的微結(jié)構(gòu)及電學(xué)性能的影響主要存在以下幾種規(guī)律：i,Ge含量的增加引起Xs--si減小,薄膜的整體晶化率減小。此時(shí),雖然薄膜中的Ge懸掛鍵增加,但致密性變好。暗電導(dǎo)率單調(diào)減小,光電導(dǎo)率先減小后增大,薄膜的光敏性存在一個(gè)極大值；ii,Ge含量不變,隨晶化率的提高,薄膜的H含量減小,結(jié)構(gòu)因子R增加,晶粒增大,暗電導(dǎo)率增加,光電導(dǎo)率先增加后減小,當(dāng)XSi-Si處于45～60%時(shí),薄膜的光敏性達(dá)到了最大值；iii,Xsi-Si固定時(shí),隨Ge含量的增加,光電導(dǎo)率下降,暗電導(dǎo)率增加,薄膜光敏性下降。此時(shí),繼續(xù)增加Ge含量(大于70%)時(shí),光、暗電導(dǎo)率明顯增大,薄膜喪失光敏性；iv,通過調(diào)節(jié)工藝條件(如減小電極間距),使Ge含量和XSi-Si同時(shí)增加。隨著Ge含量和XSi-Si的增加,薄膜H含量減小,結(jié)構(gòu)較致密,光敏性存在最大值。 2)Ge含量大于60%時(shí),通過提高氫稀釋率或減小氣體總流量等方法,可增加Si-Ge和Ge-Ge在有序結(jié)構(gòu)中的含量,薄膜的晶化率增加。此時(shí),薄膜晶粒尺寸較大,H含量較小,空洞數(shù)量和懸掛鍵含量增加。隨著Ge含量的增加,薄膜的光電導(dǎo)率下降,暗電導(dǎo)率增加,光敏性大幅下降。 其次,系統(tǒng)研究了制備參數(shù)對μc-Si1-xGex:H薄膜光吸收特性的影響,并結(jié)合高壓高功率技術(shù),使薄膜同時(shí)獲得高吸收系數(shù)和較好的電學(xué)性質(zhì)。確定了低Ge含量下(≤25%),器件質(zhì)量級μC-Si1-xGex:H薄膜的結(jié)構(gòu)及實(shí)驗(yàn)參數(shù)。我們發(fā)現(xiàn)：減小電極間距、增加襯底溫度或提高氫稀釋均可使微晶硅鍺薄膜的光吸收系數(shù)單調(diào)增加；而在氣體總流量、輝光功率和沉積氣壓系列中,隨著Ge含量的增加,光吸收系數(shù)都是先增加后減小。在基本實(shí)驗(yàn)參數(shù)得到優(yōu)化的基礎(chǔ)上,引入高壓高功率技術(shù),Ge懸掛鍵的減少改善了薄膜的電學(xué)性能；同時(shí),薄膜總的有序度增加,空洞減少,結(jié)構(gòu)更致密,這些促使了光吸收系數(shù)的增加。Ge含量小于25%的器件質(zhì)量級μc-Si1-xGex:H薄膜及Ge含量處在25--45%區(qū)間的光電性能較好的μC-Si1-xGex:H薄膜的典型特征如下：1)Ge含量小于25%的薄膜：材料的暗電導(dǎo)率在10--10-S.cm-1；光敏性在1000～1500；1000nm處的光吸收系數(shù)大于103cm-1；Si-Si晶化率為45-60%；H濃度在6-8%；XRD測試結(jié)果給出(220)擇優(yōu)取向；晶粒大小在15-20nm之間；結(jié)構(gòu)因子R小于0.3；Ge-H優(yōu)先因子大于0.5；2)25～45%Ge含量的薄膜：材料的暗電導(dǎo)在10-～10-6S·cm-1；光敏性在500～700；1000nm處的光吸收系數(shù)大于5×103cm-1；Si-Si晶化率40～55%；H濃度在5-7%；XRD測試結(jié)果給出(220)擇優(yōu)取向；晶粒大小在15-25nm之間；結(jié)構(gòu)因子R小于0.45；Ge-H優(yōu)先因子大于0.2。 最后,為了充分發(fā)揮高Ge含量μc-Si1-xGex:H薄膜在拓展光譜響應(yīng)和提高長波光吸收系數(shù)方面的優(yōu)勢,我們采用H2和He為稀釋氣體,進(jìn)一步優(yōu)化了高鍺含量(～40%)的μc-Si1-xGex:H薄膜的微結(jié)構(gòu),改善其電學(xué)性質(zhì),使其具有較好的光電性能。He在等離子體中,發(fā)生“潘寧電離效應(yīng)”,為薄膜的生長提供了額外的動(dòng)量和能量。He的摻入能夠抑制高Ge含量薄膜生長過程中H與Si優(yōu)先鍵合的問題,減少Ge懸掛鍵,增加薄膜生長表面反應(yīng)基團(tuán)的遷移能力,從而優(yōu)化了薄膜的電學(xué)性能。存在優(yōu)化的He/H2稀釋比,獲得光敏性為1300、光電性能較好的40%Ge含量的μc-Si1-xGex:H薄膜。
[Abstract]:Silicon based thin film solar cells have been attracting more and more attention and developed rapidly because of their low cost and other potential advantages. The laminated solar cells can effectively improve the conversion efficiency and stability of silicon based thin film batteries, which have become a hot issue in the field of silicon film research. The hydrogenated microcrystalline silicon germanium film (c-Si1-xGex:H) has narrow band because of its narrow band. Gap, adjustable bandgap, high absorption coefficient and other advantages, is one of the ideal choice of the active battery layer materials for stacked batteries, and has broad application prospects.
However, the complex phase structure (amorphous phase, crystal phase, grain boundary and cavity) and the chemical bonds of various alloy configurations (Si-Si, Si-Ge, Ge-Ge and (Si (Ge) -Hn) n are present in the c-Si1-xGcx:H thin films, which bring some difficulties to the analysis and optimization of the properties of the thin films. In this paper, the electrical properties and optical absorption properties of the thin film are systematically studied by RF-PECVD technology. The main research contents and results are as follows:
First, starting from the two structural parameters of Ge content (0 ~ 100%) and crystallization rate (Si-Ge, Si-Ge, Ge-Ge), the microstructures and the effects on the electrical properties of the thin films under the different Ge content are systematically studied.
1) when the content of Ge is less than 60%, the bonding (Si-Ge and Ge-Ge) related to Ge is more easily in the amorphous grid. The crystallization rate of the film depends on the order of the Si-Si bond (XSi-Si) and the content of Ge. The microstructure and electricity of the film are found by the test and analysis of the microcrystalline silicon germanium film prepared under different conditions. The change of the Ge content and the crystallization rate of the film on the film is microstructure and electrical. The main effects of the performance are as follows: I, the increase of the content of Ge causes Xs--si to decrease and the overall crystallization rate of the thin film decreases. At this time, although the Ge suspension bond in the film increases, the density becomes better, the dark conductivity decreases monotonously, the photoconductivity increases first, and the photosensitivity of thin films has a maximum value; II, Ge content is unchanged. With the increase of crystallization rate, the H content of the film decreases, the structure factor R increases, the grain size increases, the dark conductivity increases, the photoconductivity increases first and then decreases. When XSi-Si is 45 ~ 60%, the photosensitivity of the film reaches the maximum value. When III, Xsi-Si is fixed, the photoconductivity decreases, the dark conductivity increases and the film photosensitivity decreases with the increase of Ge content. When the content of Ge is increased (more than 70%), the light, the dark conductivity obviously increases and the film loses the photosensitivity. IV, by adjusting the technological conditions (such as reducing the electrode spacing), the content of Ge and the XSi-Si are increased simultaneously. With the increase of Ge content and XSi-Si, the content of H in the film decreases, the structure is more compact, and the photosensitivity has the maximum value.
2) when the content of Ge is greater than 60%, the content of Si-Ge and Ge-Ge in the ordered structure can be increased by increasing the hydrogen dilution rate or reducing the total gas flow rate. The crystallization rate of the film is increased. At this time, the size of the thin film is larger, the content of H is smaller, the number of holes and the content of the suspended key are increased. With the increase of Ge, the photoconductivity of the film decreases and the dark electricity is reduced. The conductivity increased and the photosensitivity decreased significantly.
Secondly, the influence of the preparation parameters on the optical absorption characteristics of the c-Si1-xGex:H thin film is systematically studied, and the high absorption coefficient and the better electrical properties are obtained at the same time with high voltage and high power technology. The structure and experimental parameters of the low Ge content (less than 25%), the quality level of the device and the experimental parameters are determined. We find that the electrode spacing is reduced. The absorption coefficient of the microcrystalline silicon germanium film increases monotonously by increasing the substrate temperature or increasing the hydrogen dilution, and in the total gas flow, the glow power and the deposition pressure series, with the increase of the Ge content, the optical absorption coefficient is increased first and then decreases. On the basis of the optimization of the basic experimental parameters, the high voltage high power technology is introduced, and the Ge suspension is introduced. The decrease of the bond bond improves the electrical properties of the film. At the same time, the overall order of the film is increased, the cavity is reduced, and the structure is more compact. These have prompted the optical absorption coefficient to increase the.Ge content less than 25% of the device mass grade mu c-Si1-xGex:H film and the typical characteristics of the Ge thin film with better photoelectric performance in the 25--45% interval. Below: 1) thin film with Ge content less than 25%: the dark conductivity of the material is 10--10-S.cm-1; the photosensitivity is 1000~1500; the optical absorption coefficient of 1000nm is greater than 103cm-1; Si-Si crystallization rate is 45-60%; H concentration is 6-8%; XRD test results give (220) preferred orientation; grain size is between 15-20nm; structural factor R is less than 0.3; Ge-H priority causes The thin film with the content of 0.5 and 2) is 25 ~ 45%Ge: the dark conductance of the material is 10- to 10-6S. Cm-1; the photosensitivity is 500~700; the optical absorption coefficient of the 1000nm is greater than 5 x 103cm-1; the Si-Si crystallization rate is 40 to 55%; the H concentration is 5-7%; the XRD test results give the preferred orientation; the grain size is between the 15-25nm and the structural factor R is less than 0.45. H priority factor is greater than 0.2.
Finally, in order to give full play to the advantages of the high Ge content of the thin film of the c-Si1-xGex:H film in expanding the spectral response and increasing the absorption coefficient of the long wave light, we use H2 and He as diluting gases to further optimize the microstructure of the high germanium content (~ 40%) of the Mu c-Si1-xGex:H thin film, improve its electrical properties, and make it have good photoelectric properties.He at the same time. The "Pan Ning ionization effect" occurs in the subbody, which provides additional momentum and energy.He for the growth of the thin film, which can inhibit the H and Si preferential bonding during the growth of high Ge content, reducing the Ge suspension key and increasing the migration ability of the surface reaction group of the film growth, thus optimizing the electrical properties of the film. There is an optimized H. The e/H2 dilution ratio was obtained with a photosensitivity of 1300 and a 40%Ge c-Si1-xGex:H film with good photoelectric properties.
【學(xué)位授予單位】：南開大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TM914.4;TN304.1
本文編號：2153907
[Abstract]:Silicon based thin film solar cells have been attracting more and more attention and developed rapidly because of their low cost and other potential advantages. The laminated solar cells can effectively improve the conversion efficiency and stability of silicon based thin film batteries, which have become a hot issue in the field of silicon film research. The hydrogenated microcrystalline silicon germanium film (c-Si1-xGex:H) has narrow band because of its narrow band. Gap, adjustable bandgap, high absorption coefficient and other advantages, is one of the ideal choice of the active battery layer materials for stacked batteries, and has broad application prospects.
However, the complex phase structure (amorphous phase, crystal phase, grain boundary and cavity) and the chemical bonds of various alloy configurations (Si-Si, Si-Ge, Ge-Ge and (Si (Ge) -Hn) n are present in the c-Si1-xGcx:H thin films, which bring some difficulties to the analysis and optimization of the properties of the thin films. In this paper, the electrical properties and optical absorption properties of the thin film are systematically studied by RF-PECVD technology. The main research contents and results are as follows:
First, starting from the two structural parameters of Ge content (0 ~ 100%) and crystallization rate (Si-Ge, Si-Ge, Ge-Ge), the microstructures and the effects on the electrical properties of the thin films under the different Ge content are systematically studied.
1) when the content of Ge is less than 60%, the bonding (Si-Ge and Ge-Ge) related to Ge is more easily in the amorphous grid. The crystallization rate of the film depends on the order of the Si-Si bond (XSi-Si) and the content of Ge. The microstructure and electricity of the film are found by the test and analysis of the microcrystalline silicon germanium film prepared under different conditions. The change of the Ge content and the crystallization rate of the film on the film is microstructure and electrical. The main effects of the performance are as follows: I, the increase of the content of Ge causes Xs--si to decrease and the overall crystallization rate of the thin film decreases. At this time, although the Ge suspension bond in the film increases, the density becomes better, the dark conductivity decreases monotonously, the photoconductivity increases first, and the photosensitivity of thin films has a maximum value; II, Ge content is unchanged. With the increase of crystallization rate, the H content of the film decreases, the structure factor R increases, the grain size increases, the dark conductivity increases, the photoconductivity increases first and then decreases. When XSi-Si is 45 ~ 60%, the photosensitivity of the film reaches the maximum value. When III, Xsi-Si is fixed, the photoconductivity decreases, the dark conductivity increases and the film photosensitivity decreases with the increase of Ge content. When the content of Ge is increased (more than 70%), the light, the dark conductivity obviously increases and the film loses the photosensitivity. IV, by adjusting the technological conditions (such as reducing the electrode spacing), the content of Ge and the XSi-Si are increased simultaneously. With the increase of Ge content and XSi-Si, the content of H in the film decreases, the structure is more compact, and the photosensitivity has the maximum value.
2) when the content of Ge is greater than 60%, the content of Si-Ge and Ge-Ge in the ordered structure can be increased by increasing the hydrogen dilution rate or reducing the total gas flow rate. The crystallization rate of the film is increased. At this time, the size of the thin film is larger, the content of H is smaller, the number of holes and the content of the suspended key are increased. With the increase of Ge, the photoconductivity of the film decreases and the dark electricity is reduced. The conductivity increased and the photosensitivity decreased significantly.
Secondly, the influence of the preparation parameters on the optical absorption characteristics of the c-Si1-xGex:H thin film is systematically studied, and the high absorption coefficient and the better electrical properties are obtained at the same time with high voltage and high power technology. The structure and experimental parameters of the low Ge content (less than 25%), the quality level of the device and the experimental parameters are determined. We find that the electrode spacing is reduced. The absorption coefficient of the microcrystalline silicon germanium film increases monotonously by increasing the substrate temperature or increasing the hydrogen dilution, and in the total gas flow, the glow power and the deposition pressure series, with the increase of the Ge content, the optical absorption coefficient is increased first and then decreases. On the basis of the optimization of the basic experimental parameters, the high voltage high power technology is introduced, and the Ge suspension is introduced. The decrease of the bond bond improves the electrical properties of the film. At the same time, the overall order of the film is increased, the cavity is reduced, and the structure is more compact. These have prompted the optical absorption coefficient to increase the.Ge content less than 25% of the device mass grade mu c-Si1-xGex:H film and the typical characteristics of the Ge thin film with better photoelectric performance in the 25--45% interval. Below: 1) thin film with Ge content less than 25%: the dark conductivity of the material is 10--10-S.cm-1; the photosensitivity is 1000~1500; the optical absorption coefficient of 1000nm is greater than 103cm-1; Si-Si crystallization rate is 45-60%; H concentration is 6-8%; XRD test results give (220) preferred orientation; grain size is between 15-20nm; structural factor R is less than 0.3; Ge-H priority causes The thin film with the content of 0.5 and 2) is 25 ~ 45%Ge: the dark conductance of the material is 10- to 10-6S. Cm-1; the photosensitivity is 500~700; the optical absorption coefficient of the 1000nm is greater than 5 x 103cm-1; the Si-Si crystallization rate is 40 to 55%; the H concentration is 5-7%; the XRD test results give the preferred orientation; the grain size is between the 15-25nm and the structural factor R is less than 0.45. H priority factor is greater than 0.2.
Finally, in order to give full play to the advantages of the high Ge content of the thin film of the c-Si1-xGex:H film in expanding the spectral response and increasing the absorption coefficient of the long wave light, we use H2 and He as diluting gases to further optimize the microstructure of the high germanium content (~ 40%) of the Mu c-Si1-xGex:H thin film, improve its electrical properties, and make it have good photoelectric properties.He at the same time. The "Pan Ning ionization effect" occurs in the subbody, which provides additional momentum and energy.He for the growth of the thin film, which can inhibit the H and Si preferential bonding during the growth of high Ge content, reducing the Ge suspension key and increasing the migration ability of the surface reaction group of the film growth, thus optimizing the electrical properties of the film. There is an optimized H. The e/H2 dilution ratio was obtained with a photosensitivity of 1300 and a 40%Ge c-Si1-xGex:H film with good photoelectric properties.
【學(xué)位授予單位】：南開大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TM914.4;TN304.1
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