Device physics of inverted all-polymer solar cells
Device physics of inverted all-polymer solar cells
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DOI：
10.1063/1.3371364
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发表时间：
2010-06-01
影响因子：
3.2
通讯作者：
McNeill, Christopher R.
中科院分区：
文献类型：
--
作者：
Brenner, Thomas J. K.;Hwang, Inchan;McNeill, Christopher R.
研究了由聚（3-己基噻吩）和聚（9，9-二辛基芴）-2，7-二基-alt-[4，7-双（3-己基噻吩-5-基）2，1，3-苯并噻二唑]-2 '，2（''）-二基）共混的倒置全聚合物太阳能电池的器件物理。特别是，有源层厚度对器件参数的影响进行了研究，并与具有标准几何形状的器件进行了比较。将有源层厚度从70 nm增加到480 nm，发现开路电压从0.1 V增加到0.71 V，外量子效率（EQE）从7%增加到24%。与此相反，一个最佳的EQE约为25%的标准几何被发现为70 nm的膜厚度，这急剧下降，增加活性层厚度。标准几何结构器件的EQE光谱的形状也随着有源层厚度的增加而变得严重失真，其中EQE的最小值与对应于最大光吸收的波长一致。相反，倒置器件的EQE谱的形状随着有源层厚度的增加而基本保持不变。在有源层中的光吸收的光学模拟也已经进行，并证明，在较厚的标准几何形状的设备的EQE光谱的失真是一致的，在这些设备的后半部分中创建的光激发被更有效地收获比那些在第一个100 nm的倒置设备。此外，倒置器件的EQE光谱不会随着厚度的增加而显著加宽的事实表明，光激发的捕获在器件的前半部分中保持有效，其中大部分光被吸收。器件建模表明，较低的迁移率的电子（和电子捕获）导致一个有利的重新分布的内部电场在倒置的设备与电场增加附近的透明电极符合最大光吸收的区域。相比之下，在标准器件中，内部电在透明电极附近显著降低，导致场依赖性电荷分离的降低和双分子复合的增加。我们的研究结果表明，倒置器件可能是一种有效的方式来克服有机太阳能电池中的电子迁移率通常低于空穴迁移率的损失。(C)2010年美国物理学会。[doi：10.1063/1.3371364]
The device physics of inverted all-polymer solar cells based on a blend of the polymers poly(3-hexylthiophene) and poly(9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthiophen-5-yl)2,1,3-benzothiadiazole]-2',2('')-diyl) is investigated. In particular, the influence of active layer thickness on device parameters is investigated and compared to that of devices with a standard geometry. Increasing the active layer thickness from 70 to 480 nm is found to increase the open circuit voltage from 0.1 to 0.71 V and the external quantum efficiency (EQE) from 7% to 24%. In contrast, an optimum EQE of about 25% for the standard geometry is found for a film thickness of 70 nm, which decreases sharply with increasing active layer thickness. The shape of the EQE spectra of standard geometry devices also become severely distorted with increasing active layer thickness, with a minimum in EQE coinciding with the wavelength corresponding to maximum light absorption. In contrast, the shape of the EQE spectra of inverted devices remains essentially unchanged with increasing active layer thickness. Optical simulations of light absorption in the active layer have also been performed and demonstrate that the distortion in the EQE spectra of thicker standard geometry devices is consistent with photoexcitations created in the back half of these devices being more efficiently harvested than those in the first 100 nm of the inverted device. Furthermore, the fact that the EQE spectrum of inverted devices does not significantly broaden with increasing thickness suggests that harvesting of photoexcitations remains efficient in the front half of the device where most of the light is absorbed. Device modeling is employed to demonstrate that the lower mobility of electrons (and electron trapping) causes a favorable redistribution of the internal electric field in the inverted device with electric field increasing near the transparent electrode coinciding with the region of maximum light absorption. In contrast, in the standard device the internal electric significantly decreases near the transparent electrode causing a reduction in field-dependent charge separation and increased bimolecular recombination. Our results demonstrate that inverted devices may be an effective way to overcome losses in organic solar cells where electron mobility is typically lower than hole mobility. (C) 2010 American Institute of Physics. [doi:10.1063/1.3371364]