本研究主要是利用共軛高分子聚合物P3HT：PCBM之單層異質接面結構做為有機感光層，嘗試製作有機光感測器元件，經由製程的改善後，在太陽模擬光源照射之下成功地觀測到其受光二極體的特性與其光/暗電流的差異；並且透過改變有機感光層的膜厚、退火溫度及退火時間三種製程參數，來提昇元件的光電流值及光/暗電流對比值，歸納出在感光層膜厚140nm、退火溫度90℃及退火時間10分鐘的條件與-2V的操作電壓之下，最大可達到350倍的光/暗電流對比。
本研究所使用的有機高分子原料因受環境的影響，應用於有機太陽能電池時，其最大光電轉換功率為0.008%，而應用於有機光感測器時，其最大平均光/暗電流對比可達到240倍，且改用一般光源取代太陽模擬光源作照光量測後，元件的光/暗電流對比值仍可達到約100倍。此外本研究發現將元件保存於氮氣環境下，可減緩其元件壽命的衰退速率。

The objectives in this thesis are to fabricate an organic polymer-based photosensor by using bulk heterojunction structures of two conjugated polymers, poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), as an organic active layer. The phenomena of photodiode are successfully observed under simulated solar light illumination. The optimum value of the ratio between light and dark currents is about 350 times at a reverse bias voltage -2V when the fabrication parameters for active layer are annealing temperature 90℃, annealing time 10 minutes, and active layer thickness 140 nm.
Some literatures mentioned P3HT and PCBM are very sensitive and should be protected from oxygen or air during material preparation. In our study, P3HT and PCBM material are prepared in air envioroment. The photosensor can achieve 240 in light and dark current ratio even if the maximum power conversion efficiency (PCE) of device was only 0.008% for solar cell application. When a simulated solar light source was replaced by white light source, the ratio between light and dark currents could still reach 100 times. The efficiency of photosensor will decay if stored in normal air condition. It is also found that the degrade of efficiency will be slowed down if the device was stored in a pure nitrogen environment.

[1] B. O'Regan and M. Grätzel, “A low-cost, high-efficiency solar cell based on dye- sensitized colloidal TiO2 films”, Nature, 353, pp.737-740, 1999

[2] S. E. Shaheen, R. Radspinner and N. Peyghambarian, “Fabrication of bulk heterojunction plastic solar cell by screen printing”, Appl. Phys. Lett., 79, pp.2996-2998 , 2001

[3] J. Bharathan and Y. Yang, “Polymer electroluminescent devices processed by inkjet printing:1. Polymer light emitting logo”, Appl. Phys. Lett., 72, pp.2660-2662, 1998

[4] C. J. Brabec, F. Padinger, J. C. Hummelen, R. A. Janssen and N. S. Sariciftci, “Realization of large area flexible fullerene-conjugated polymer photocells:A route to plastic solar cells”, Synth. Met., 102, pp.861-864, 1999

[5] S. A. Chen, 物理雙月刊, P.312, April, 2001

[6] H. Shirakawa, E.J. Louis, A.G. MacDiarmid, C.K. Chiang and A.J. Heeger, J. Chem.Soc. Chem. Commun., 16, 578, 1977

[7] Dipl.Ing. Klaus Petritsch, “Organic Solar Cell Architectures”, Cambridge and Graz, 2000

[8] N. S. Sariciftci, L. Smilowitz, A. J. Heeger and F. Wudl, “Photoinduced electron transfer from a conducting polymer to buckminsterfullerene”, Science, 258, pp.1474-1476, 1992

[9] X. G. Chin, ”Efficiency Enhancement of Polymer/Fullerene Bulk-Heterojunction Solar Cell by Blending TiO2 Nanoparticles into
Photo-active Materials”, 2005

[10] N. S. Sariciftci, D. Braun, C. Zhang, V. I. Srdanov, A. J. Heeger, G. Stucky and F. Wudl, “Semiconducting polymer-buckminsterfullerene heterojunctions: Diodes, photodiodes, and photovoltaic cells”, Appl. Phys. Lett., 62, pp.585-587, 1993

[11] G. Yu, J. Gao, J. Hummelen, F. Wudl and A. J. Heeger, “Polymer photovoltaic cells: Enhanced efficiencies via a network of internal donor-acceptor heterojunctions”, Science, 270, pp.1789-1791, 1995

[12] S. E. Shaheen, C. J. Brabec, N. S. Sariciftci, F. Padinger, T. Fromherz and J. C. Hummelen, “2.5 % efficient organic plastic solar cell”, Appl. Phys. Lett., 78, pp.841-843, 2001

[13] F. Padinger, R. S. Rittberger and N. S. Sariciftci, “Effects of postproduction treatment on plastic solar cells”, Adv. Funct. Mater., 13, pp.85-88, 2003

[14] G. Li, V. Shortriya, Y. Yao and Y. Yang, “Investigation of annealing effects and film thickness dependence of polymer solar cells based on poly(3-hexylthiophene)”, J. Appl. Phys., 98, pp.043704-1, 2005

[15] D. Chirvase, J. Parisi, J. C. Hummelen and V. Dyakonov, ”Influence of nanomorphology on the photovoltaic action of polymer–fullerene composites”, Nanotechnology , 15, pp.1317–1323, 2004

[16] http://www.simens.com

[17] Xuhua Wang ,Oliver Hofmann,bc Rupa Das,Edward M. Barrett, Andrew J. deMello, John C. deMello and Donal D. C. Bradley, ” Integrated thin-film polymer/fullerene photodetectors for on-chip microfluidic chemiluminescence detection”, Lab Chip, 7, pp.58–63, 2007

[18] Hiroyuki Shimada, Shigeki Naka, Hiroyuki Okada and Hiroyoshi Onnagawa, ”Top-Absorption Organic Photodiodes Suitable for Device Integration”, Japanese Journal of Applied Physics ,Vol. 44, No. 4B, pp.2830–2832, 2005

[19] J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K. Mackay, R. H. Friend, P. L. Burn and A. B. Holomes, “Light-emitting diodes based on conjugated polymers”, Nature, 347, 539, 1990

[20] 蔡進譯, 物理雙月刊, 27, 5, 2005

[21] http://teacher.ksvs.kh.edu.tw/~yushian/data/ch2-2diode.doc

[22] 王文義, 林怡君, “高分子太陽能電池技術”, 工業材料, 203, 156, 2003

[23] H. Spanggaard and F. C. Krebs, “A brief history of the development of organic and polymeric photovoltaics”, Solar Energy Materials and Solar Cells, 83, pp.125–146, 2004

[24] P. Peumans and S. R. Forrest, “Very-high-efficiency double - heterostructure copper phthalocyanine/C60 photovoltaic cells”, Appl, Phys. Lett., 79, pp.126-128, 2001

[25] H. Hoppe and N.S. Sariciftci, “Organic solar cells:an overview”, J. Mater.Res., 19, pp.1924-1945, 2004