一般來說， p-i-n結構太陽能主要由吸收層(i-type)吸光後產生光生載子電子電洞對，光生載子會經由元件內建電場將其導出至外部電路形成光生電流。但由於電洞傳輸能力遠低於電子，因此在被導出至外部電路前，電洞大部分會與薄膜內部缺陷產生復合而造成光電流大小受限的情形。換句話說，若元件要得到好的光電特性，則須提升自由載子傳輸能力，自由載子傳輸能力主要決定於內部電場好壞，因此改善元件內部電場可有效提升自由載子傳輸能力進而提升太陽能電池之光電流。
在本研究中，太陽能電池吸收層主要採用非晶矽鍺薄膜，矽鍺薄膜可藉由改變鍺的比例將能隙調變範圍由1.1eV至1.8eV，由於可調變的特點使矽鍺薄膜常應用於串疊式太陽能電池結構以增加光吸收大小，並常應用於中間層太陽能電池結構或是最底層式太陽能電池。
漸變矽鍺吸收層太陽能電池和加入微晶結構摻雜層(p-type and n-type)太陽能電池是由雷射輔助電漿增強式化學氣相沉積系統所成長，由實驗結果可證明，在引入漸變吸收層結構後，太陽能電池元件之光電流值可由19.43提升至23.54 mA/cm2，效率可由5.46%提升至6.83%。為了更進一步提升太陽能電池之元件特性，將具漸變吸收層太陽能電池元件之p型薄膜以及n型薄膜應用雷射輔助電將增強式化學氣相沉積系統製作為微晶矽結構，利用微晶矽薄膜之高導電度及低電阻率之特點，更可進一步將光電流值提升至26.30 mA/cm2，元件效率提升至7.51%。

In general, a solar cell structure consists of an absorber layer, in which the photons of an incident radiation are efficiently absorbed resulting in a creation of electron-hole pairs. The photo-generated electrons and holes are driven by the built-in electric field of the junction to form the photo-current. The transmission capacity of electron was much better than the hole. Therefore, before the holes were driven to the contacts, the holes were recombined at defects. As this result, the photo-current is diminished. On other words, to obtain high performance, the transmission capacity of hole should be improved. On the other hand, the transmission capacity is determined by the built-in electric field, in which it should be as high as possible .
In this study, the a-SiGe thin film was applied to the absorber layer of solar cells. The energy band-gap of amorphous silicon–germanium (a-SiGe) alloy can be adjusted continuously between 1.4 eV and 1.8 eV by varying the Ge fraction. This characteristic renders a-SiGe a suitable light absorber material in multi-junction amorphous silicon (a-Si) based thin film solar cells, in which the a-SiGe acts as intrinsic layer in middle or bottom cells to enhance green to red absorption .
The high performance silicon-germanium (a-SiGe) solar cells with graded absorber layer and microcrystalline structure doped thin films (p-Si and n-Si) was fabricated by using laser-assisted plasma-enhanced chemical vapor deposition (LAPECVD) system. These experimental results verified that the solar cells with graded absorber layer was improved from 19.43 mA/cm2 to 23.54 mA/cm2. Consequently, the conversion of the solar cells efficiency was upgraded from 5.46 % to 6.83 %.
Furthermore, the short circuit current density of the solar cells with graded absorber and microcrystalline structure doped thin films (p-Si and n-Si) layer was improved from 19.43 mA/cm2 to 26.3 mA/cm2. Consequently, the conversion of the solar cells efficiency was upgraded from 5.46 % to 7.51 %.

Chapter 1

[1] H. F. Sterling, and R. C. G. Swann, “Chemical vapor deposition promoted by r.f. discharge”, Solid-State Electron., vol. 8, pp. 653-654, 1965.
[2] W. E. Spear, and P. G. L. Comber, “Substitutional doping of amorphous silicon”, Solid State Commun., vol. 17, pp.1193-1196, 1975.
[3] W. E. Spear, and P. G. L. Comber, “Electronic properties of substitutionally doped amorphous Si and Ge”, Phil. Mag., vol. 33, pp. 935-949, 1976.
[4] 戴寶通、 鄭晃忠(2008)， 太陽能電池技術手冊， 新竹市： 台灣電子材料與元件協會， 頁 169-170。
[5] J. Kim, A. K. Ahmed, A. J. Hong, M. M. Saad, D. K. Sadana, and T. C. Chen, ”Efficiency enhancement of a-Si:H single junction solar cells by a-Ge:H incorporation at the p+ a-SiC:H/transparent conducting oxide interface,” Appl. Phys. Lett., vol. 99, pp. 062102-062105, 2011.
[6] T. Matsui1, C. W. Chang, T. Takada1, M. Isomura, H. Fujiwara, and M. Kondo, “Microcrystalline Si1-xGex Solar Cells Exhibiting Enhanced Infrared Response with Reduced Absorber Thickness,” Appl. Phys. Express., vol. 1, pp. 031501-1-031501.3, 2008.
[7] S.M. Sze(2002), Semiconductor Devices(2nd ed.), New Jersey: John Wiley & Sons.

Chapter 2

[1] 翁敏航、楊茹媛、管鴻、晁成虎(2012)， 太陽能電池原理、元件、材料、製成與檢測技術， 台北市： 東華書局， 頁 397-398。
[2] 施敏(2008)， 半導體元件與製作技術第二版， 新竹市：國立交通大學出版社， 頁 51-52。
[3] W. T. Tsang, “Light Communication Technology,” Academic Press.

Chapter 4

[1] 戴寶通、 鄭晃忠(2008)， 太陽能電池技術手冊， 新竹市： 台灣電子材料與元件協會， 頁 178-179。
[2] W. Paul, “Structural, optical and photoelectronic properties of improved PECVD a-Ge:H”, Non-Cryst. Solids, vol. 137-138, pp. 803-808, 1991.
[3] D. P. Stieler, “Measurement of mobility in nanocrystalline semiconductor materials using space charge limited current”, Iowa State University, 2005.
[4] A. Eray, and G. Nobile, “Evaluation of the gapstate distribution in a-Si:H by SCLC measurements”, Sol. Energy Mater. Sol. Cells, vol. 76, pp. 521-528, 2003.