Effect of annealing-induced oxidation of molybdenum oxide on organic photovoltaic device performance
Effect of annealing-induced oxidation of molybdenum oxide on organic photovoltaic device performance
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DOI：
10.1016/j.orgel.2016.06.024
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发表时间：
2016-10
影响因子：
3.2
通讯作者：
T. Kobori;N. Kamata;T. Fukuda
中科院分区：
文献类型：
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作者：
T. Kobori;N. Kamata;T. Fukuda
氧化钼（MoOx）作为空穴传输层被广泛应用于有机光伏电池（OPV）中，在有机活性层和透明阳极之间插入MoOx层可以有效地分解载流子，从而提高OPV的性能。在这项研究中，热退火MoOx对OPV的光伏性能的影响进行了研究，使用低能带隙聚合物和[6，6]-苯基C71-丁酸甲酯（PC 71 BM）的共混物薄膜作为活性层。我们使用了三种低带隙聚合物：聚[2，6-（4，4-双-（2-乙基己基）-4H-环戊二烯并[2，1-B]; 3，4-B′]二噻吩）-alt-4，7（2，1，3-苯并噻二唑）]（PCPDTBT），聚乙烯（4，8-双[（2-乙基己基）氧基]苯并[1，2-B：4，5-B′]二噻吩-2，6-二基3-氟-2-[（2-乙基己基）羰基]噻吩并[3，4-B]噻吩二基）（PTB 7）和聚乙烯（[2，6 ′-4，8-二（5-乙基己基噻吩基）苯并[1，2-B，3，3-B]二噻吩]3-氟-2 [（2-乙基己基）羰基]噻吩并[3，4-B]噻吩二基）（PTB 7-Th）。当在160 °C下对所沉积的MoOx层退火5分钟时，所有研究的聚合物的功率转换效率都大幅增加。特别地，当使用PTB 7时实现了6.57%的高效率;为了比较，具有沉积态MoOx层（未经历退火）的参考器件的效率为1.40%。具体来说，退火后短路电流密度和填充因子显着提高，这意味着有源层中实现了有效的载流子解离。我们评估了光吸收和表面形态，以阐明光伏性能改善的原因，这些参数在退火后仅略有变化。与此相反，角度依赖的X射线光电子能谱显示，MoOx层被氧化后退火。通常，MoOxs的氧空位作为载流子陷阱;载流子陷阱数量的减少导致有机层中的高空穴迁移率，这反过来又导致改善的光伏性能。因此，我们的研究结果表明，退火诱导氧化的MoOx是有用的，以实现高的光伏性能。
Molybdenum oxide (MoOx) has been widely used as a hole transport layer in organic photovoltaic cells (OPVs), whose performance can be improved by inserting a MoOxlayer between an organic active layer and a transparent anode because of efficient carrier dissociation. In this study, the influence of thermally annealed MoOxon the photovoltaic performance of OPVs was first investigated using low-bandgap polymer and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) blend films as the active layer. We used three low-bandgap polymers: poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT), poly(4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl) (PTB7), and poly([2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b,3,3-b]dithiophene]3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl) (PTB7-Th). Power conversion efficiencies were drastically increased for all investigated polymers when the as-deposited MoOxlayer was annealed at 160 °C for 5 min. In particular, a high efficiency of 6.57% was achieved when PTB7 was used; for comparison, the efficiency of a reference device with an as-deposited MoOxlayer (not subjected to annealing) was 1.40%. Specifically, the short-circuit current density and fill factor were remarkably improved after annealing, which means that efficient carrier dissociation was achieved in the active layer. We evaluated optical absorption and surface morphology to elucidate reasons behind the improved photovoltaic performance, and these parameters only slightly changed after annealing. In contrast, angle-dependent X-ray photoelectron spectroscopy revealed that the MoOxlayer was oxidized after annealing. In general, the oxygen vacancies of MoOxact as carrier traps; a reduction in the number of carrier traps causes high hole mobility in the organic layer, which, in turn, results in an improved photovoltaic performance. Therefore, our results indicate that the annealing-induced oxidation of MoOxis useful for achieving high photovoltaic performance.