有機高分子太陽能電池之碳酸銫介面層研究

A Functional Interlayer of Cesium Carbonate for Polymer Photovoltaic Devices

吳志力(Jyh-Lih Wu)

指導教授 ： 楊士禮

國立清華大學/電機資訊學院/光電工程研究所/碩士(2007年)

摘要

本研究主要探討加入碳酸銫(Cs2CO3)作為介面層之後的元件特性(Blend/Cs2CO3/Al)，電子注入的機制，以及元件後熱退火對元件特性的影響。結果發現：在陰極鋁與主動層間加入一極薄的Cs2CO3作為介面層，可以有效地提升元件的開路電壓和填充係數，進而提升有機太陽能電池的功率轉換效率，元件的開路電壓為0.57 V，短路電流密度為9.45 mA/cm2，填充係數可達0.60，而功率轉換效率可達到3.05%。從光電子能譜儀的測量結果可發現，加入Cs2CO3作為介面層之後，會有電子轉移至主動層，使有機物產生N-型攙雜，幫助電子的注入，進而降低元件的串聯電阻。同時，我們由開路電壓對溫度的關係圖可以求得元件開路電壓的最大值，結果發現加入Cs2CO3作為介面層後，元件開路電壓的最大值為1.02 V，此值相當接近donor的HOMO與acceptor的LUMO之能階差，因而可證實Cs2CO3/Al電極可形成較好的歐姆接觸。此外，在ITO/PEDOT: PPS/P3HT: PCBM/Cs2CO3/Al元件做元件後熱退火處理後，從AFM圖可得知，陰極與主動層間的接合度獲得改善，避免在主動層與陰極間介面附近形成缺陷，進而減少漏電路徑並提升元件的並聯電阻，當元件後熱退火處理的條件為140 ˚C，為時四分鐘，元件的功率轉換效率可以提升至3.70%。

關鍵字

有機太陽能電池 ； 碳酸銫 ； 元件後熱退火

並列摘要

In this study, we mainly investigated the cell characteristics of Blend/Cs2CO3/Al devices, the electron-injection mechanism of the Cs2CO3/Al cathode, as well as the post-annealing effect on the device performance. We found that an insertion of Cs2CO3 improves the device performances including Voc, FF, and PCE. In the device of Blend/Cs2CO3/Al, a Voc of 0.57 V, a Jsc of 9.45 mA/cm2, a FF of 0.60, and a PCE of 3.05% were achieved. The result of XPS measurement revealed that a portion of electrons would be transferred into the active blend after inserting an interlayer of Cs2CO3, inducing the N-type dopping of the active layer. The N-type dopping process enhances the electron injection, being responsible for the reduced series resistance of the device. Meanwhile, the maximum Voc can be determined form the temperature dependence of Voc. The (Voc)max after inserting Cs2CO3 was found be 1.02 V which is extremely close to the corresponding value of the energy difference between the HOMO of donor and the LUMO of acceptor, suggesting that Cs2CO3/Al electrode can form a better ohmic contact. From the AFM images, the adhesion can be improved after the ITO/PEDOT: PPS/P3HT: PCBM/Cs2CO3/Al device was post-annealed. This prevents the forming of defects near the interface between the active layer and the cathode and therefore reduces leakage paths, resulting in the increase of the calculated shunt resistance. Under the optimum post-annealing condition (140 ˚C, 4 min), the power conversion efficiency of the device can be improved to 3.7%.

並列關鍵字

organic solar cells ； Cs2CO3 ； post-annealing

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