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標題: | 含氟富勒烯之塊材異質接面鈣鈦礦太陽能電池研究 Fluorinated Fullerene Derivatives as N-type Material to Fabricate High Performance Bulk Heterojunction Perovskite Solar Cell |
作者: | Chieh-Ping Wang 王捷平 |
指導教授: | 林唯芳(Wei-Fang Su) |
關鍵字: | 鈣鈦礦太陽能電池,塊材異質接面結構,氟化改質富勒烯衍生物,一步驟溶液製程,單一溶劑製程, perovskite solar cell,bulk heterojunction structure,fluorinated fullerene derivative,one-step solution process,single solvent process, |
出版年 : | 2017 |
學位: | 碩士 |
摘要: | 鈣鈦礦太陽能電池因為具備低成本、高光電轉換效率等優勢,受到許多研究學者的關注,並被視為最具發展潛力的再生能源之一。其中,p-i-n平面異質接面結構鈣鈦礦太陽能電池由於元件結構與製程相對簡單,且較無電流密度-電壓量測遲滯現象,因此逐漸成為發展主流。為了更進一步提升p-i-n平面異質接面結構鈣鈦礦太陽能電池元件表現,近年來許多研究學者嘗試將具高電子遷移率與可低溫溶液製程特性的富勒烯衍生物(PC61BM)混摻入鈣鈦礦光吸收層中,以製備塊材異質接面鈣鈦礦薄膜。藉由增加材料間的異質接面而增加激子分離的可能性,進而提升元件表現。然而,由於PC61BM在鈣鈦礦前驅物溶液中溶解性不佳,導致現階段塊材異質接面鈣鈦礦光吸收層之製程相對繁瑣。因此在本研究中,引入氟化改質PC61BM(3F-PC61BM與5F-PC61BM),利用其支鏈的氟化改質提升PC61BM在鈣鈦礦加工溶劑中的溶解性,進而開發出一步驟、單一溶劑的塊材異質接面鈣鈦礦薄膜製程。
經實驗發現,由於3F-PC61BM自聚集現象較不明顯,因此在少量的混摻濃度下(0.1 wt%),能引導鈣鈦礦晶粒形成緻密的薄膜,提升元件表現。電流密度從未混摻元件的19.96 mA/cm2提升至21.78 mA/cm2,而元件效率從14.12 %提升至16.17 %。但隨著混摻濃度的提升,塊材異質接面薄膜表面會產生3F-PC61BM的團聚物,進而導致鈣鈦礦元件層與層間接觸不良,因此降低元件表現。另一方面,5F-PC61BM具有強的自聚集效應,故會形成較大團聚的異質成核點,迫使鈣鈦礦薄膜中晶粒聚集,形成不連續的孔洞狀或帶狀表面形貌。鈣鈦礦與上下層的電子、電洞傳輸層因此有極大接觸的可能性,所以不論混摻多少濃度之5F-PC61BM,都會導致元件效率下降。最後,在穩定性測試方面,混摻0.1 wt% 3F-PC61BM由於能形成緻密的塊材異質接面鈣鈦礦薄膜,空氣中的水氣與氧氣較不易從薄膜中的晶界中滲入,因此元件的穩定性能有效提升。相較未混摻鈣鈦礦太陽能電池在僅240小時量測後表現已降至原來的80%,混摻0.1 wt% 3F-PC61BM的塊材異質接面鈣鈦礦太陽能電池能維持550小時表現才降至原來的80%。 總結來說,藉由調控氟化改質的數目與混摻濃度使得氟化改質PC61BM在提升溶解性與自聚集效應中取得平衡,可製備出高效率且高穩定性的鈣鈦礦太陽能電池。 Perovskite solar cells have attracted considerable attention in the past few years due to the advantages of low production cost and high power conversion efficiency (PCE). They are regarded as one of the most promising technology in renewable energy field. In the research of perovskite solar cells, p-i-n planar heterojunction (PHJ) structure is investigated extensively in recent years, which has benefits of simple fabrication process and almost no current density-voltage measurement hysteresis phenomenon. To further enhance the device performance of p-i-n PHJ perovskite solar cells, some researchers blended fullerene derivatives (PC61BM) with perovskite to fabricate bulk heterojunction (BHJ) light adsorption active layer. By increasing the contact area between perovskite and PC61BM in BHJ film, one can effectively increase the exciton dissociation probability, and the device performance can be improved. It is hard to homogeneously blend PC61BM with perovskite precursor solutions due to the poor solubility of PC61BM. Thus, the fabrication processes of perovskite: PC61BM BHJ films are always complex. To overcome these problems, in this study, we introduced fluorinated-PC61BM (3F-PC61BM and 5F-PC61BM) into perovskite film to fabricate BHJ perovskite device. With fluorinated modification, the solubility of PC61BM in processing solvent can be improved. We therefore develop a simple approach to fabricate BHJ perovskite device by using single solvent and one-step solution process. In our experimental results, blending 0.1 wt% 3F-PC61BM can provide heteronucleation sites for perovskite grains and then grow into densely packed BHJ film. Consequently, the current density and PCE can be improved from 19.96 mA/cm2 and 14.12% of pristine device to 21.78 mA/cm2 and 16.17% of 0.1 wt% 3F-PC61BM:perovskite BHJ device, respectively. However, as the blending ratio of 3F-PC61BM in BHJ film is increased, the aggregated clusters of 3F-PC61BM would appear on the surface of BHJ film and result in decreasing device performance due to the poor contact between BHJ film and electron transporting layer. On the other hand, 5F-PC61BM molecules have stronger effect of self-aggregation than 3F-PC61BM molecules. It provides large heteronucleation sites in BHJ film for perovskite grains to aggregate and form a non-continuous surface. The voids in 5F-PC61BM:perovskite BHJ films are deep enough for the direct contact between electron transporting layer and hole transporting layer, which lead to the poor device performance. Finally, in the stability test of solar cell, the densed 0.1 wt% 3F-PC61BM:perovskite BHJ film can effectively prevent the permeation of moisture and oxygen through grain boundaries. Therefore, the stability of device can be enhanced. The BHJ device can maintain 80% of their initial PCE over 550 hours while the pristine device degrades to lower than 80% after 240 hours measurement. By tuning the fluorine atoms and the blending ratio of fluorinated-PC61BM in BHJ film, we can fabricate the BHJ perovskite solar cells with high performance and stability via a one-step and single solvent process. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/59271 |
DOI: | 10.6342/NTU201701241 |
全文授權: | 有償授權 |
顯示於系所單位: | 材料科學與工程學系 |
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