臺灣博碩士論文加值系統

本研究的主題主要是利用原子層沉積技術(Atomic layer deposition, ALD)來封裝高分子太陽能電池，藉此改善此電池之壽命與減少封裝時所造成不必要的傷害。
在此我們使用目前文獻報導可以達到最高效率的材料(P3HT/ PCBM)及結構(Bulk heterojunction)來進行此研究。首先我們建立了一個製備元件的標準製程，藉由適當元件的設計以及的高分子濃度(concentration of P3HT/PCBM solution)，我們可以達到約3.74%的光能轉電能效率。
接著以此標準製程製備岀之元件進行原子層沉積封裝，首先我們必須排除因製程所造成的元件劣化。其中包括了利用:(1)修正ALD製程時間及以(2)1:0.8 (P3HT/PCBM)混合比例來取代1:1的方法解決了P3HT/PCBM因高溫、長時間下所引起的劣化 (3)在180℃下作封裝避免元件性能的衰退。
排除製程因素所造成之劣化後，我們利用約600Å的ALD薄膜改善元件的壽命(7hr~76hr)，並進一步在ALD上加一層UV膠改善元件的壽命由~7hr~到255hr。雖然ALD的封裝技術可以有效改善元件的壽命，但仍不及利用玻璃蓋封裝之元件所達之效果(~895hr)。在此我們提出幾個改善的方向:(1)利用電漿處理將元件以外之高分子(P3HT/PCBM)移除，減少在元件周圍因高分子所造成之膜的不均勻性(2)適當的調整ALD之參數進而有效的包覆整個元件，提升元件之壽命(3)利用有機無機多層堆積方法來改善元件之壽命。

This study aims to develop thin-film encapsulation using atomic layer deposition (ALD) for polymer solar cells to improve their lifetime while minimizing encapsulation-induced deterioration. For polymer solar cells the lifetime is most often defined as the time it takes for the efficiency to reach half its initial or maximum value.4
To obtain reliable vehicles with which to study encapsulation, a fabrication process for P3HT/ PCBM bulk-heterojunction solar cells was established through optimizing the cell layout and the concentration of the P3HT/PCBM solution. The optimized process yielded reproducible cells with power conversion efficiency up to 3.74 %. Encapsulation-induced deterioration of the cells was eliminated by (1) minimizing the ALD process time by modifying the deposition conditions, (2) using a P3HT/PCBM ratio of 1:0.8 instead of 1:1, and (3) setting the ALD process temperature at an optimized value of 180ºC. The lifetime of the cells was improved from ~ 7 to ~ 76 hr by encapsulation with a 600Å-thick ALD Al2O3, which was further improved 255 hr by adding a layer of a UV-curable adhesive on top of the Al2O3 layer. Although the ALD encapsulation significantly improved the cell lifetime, it was inferior to the reference encapsulation method using a glass cover slide attached by the UV adhesive, which achieved a lifetime of about 895 hr. The ALD encapsulation will be improved in the following work by (1) using plasma etching to thoroughly remove the active materials outside the cell area to minimize residues-induced defects in the ALD films, (2) fine-tuning the ALD process to improve the quality of the films, and (3) stacking the ALD films and the adhesive into multilayer encapsulation, e.g., ALD/adhesive/ ALD.

Contents
Abstract (Chinese) ii
Abstract (English) iii
Contents v
List of Figures vii
List of Tables ix

Chapter 1 Introduction 1
1.1 Background and motivation 1
1.2 The basic principles of polymer- based solar cell 3
1.3 Metal- Insulator- Metal model 6
1.4 Equivalent circuit for a solar cell 10
1.5 Bulk heterojunction solar cells 11
1.6 Donor and acceptor Materials 13
1.7 Planning for improvement 15
1.7.1 Controlling the nanomorphology 15
1.7.2 Increasing the photon absorption 15
1.7.3 Enhancement the device lifetime: Including paper review 16
1.8 Atomic layer deposition 18
Chapter 2 experiment 20
2.1 Materials 20
2.2 Device fabrication 22
2.3 Device encapsulation 25
2.4 Measurement 27
Chapter 3 Results and discussion 28
3.1 Device fabrication 28
3.1.1 Optimizing the device layout 29
3.1.2 Optimizing the concentration of the polymer solution 34
3.2 Atomic layer deposition methods on solar cells 38
3.2.1 The lifetime of devices with glass encapsulation. 39
3.2.2 The effect of ALD pump time on film’s quality 40
3.2.3 Effects of P3HT/PCBM ratio on the thermal stability 42
3.2.4 The deposition temperature of ALD effect on the performance of devices 47
3.2.5 Effects of the processing time of the ALD encapsulation process 52
3.2.6 The different methods of encapsulation influences on the lifetime of devices 53
3.2.7 The improvement of ALD process 58

Chapter 4 Conclusion and Future work 62
4.1 Conclusion 62
4.2 Future works 64
4.2.1 Device fabrication 64
4.2.2 ALD encapsulation 65
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