Carbon Nanotubes for Quantum Dot Photovoltaics with Enhanced Light Management and Charge Transport,ACS Photonics

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Carbon Nanotubes for Quantum Dot Photovoltaics with Enhanced Light Management and Charge Transport
ACS Photonics ( IF 6.5 ) Pub Date : 2018-11-08 00:00:00 , DOI: 10.1021/acsphotonics.8b00982
Yujiro Tazawa ₁ , Severin N. Habisreutinger _{2,

3} , Nanlin Zhang ₁ , Daniel A. F. Gregory ₁ , Gabriel Nagamine ₄ , Sameer V. Kesava ₂ , Giulio Mazzotta ₂ , Hazel E. Assender ₁ , Moritz Riede ₂ , Lazaro A. Padilha ₄ , Robin J. Nicholas ₂ , Andrew A. R. Watt ₁

Affiliation

Colloidal quantum dot (CQD)-based photovoltaics are an emerging low-cost solar cell technology with power conversion efficiencies exceeding 10%, i.e., high enough to be interesting for commercialization. Well-controlled and understood charge carrier transport through the device stack is required to make the next step in efficiency improvements. In this paper, polymer-wrapped single-walled carbon nanotube (SWNT) films embedded in an insulating poly(methyl methacrylate) (PMMA) matrix and capped by a thermally evaporated Au electrode are investigated as a composite hole transport layer and optical spacer. Employing transient absorption spectroscopy we show that the SWNTs enhance the charge transfer rate from CQD to CQD, ZnO, or SWNT. In order to pinpoint the underlying mechanism for the improvement, we investigate the energetics of the junction by measuring the relative alignment of the band edges, using Kelvin probe and cyclic voltammetry. Measuring the external quantum efficiency and absorption we find that the improvement is not mainly from electronic improvements but from enhanced absorption of the CQD absorber. We demonstrate experimentally and theoretically, by employing a transfer-matrix model, that the transparent PMMA matrix acts as an optical spacer, which leads to an enhanced absorption in the absorber layer. With these electronic and optical enhancements, the efficiency of the PbS CQD solar cells improved from 4.0% to 6.0%.

中文翻译：

用于量子点光伏的碳纳米管，具有增强的光管理和电荷传输能力

基于胶体量子点（CQD）的光伏技术是一种新兴的低成本太阳能电池技术，其功率转换效率超过10％，即高到足以引起商业化的兴趣。需要进行良好控制且易于理解的电荷载流子通过器件堆栈的传输，以进行下一步的效率改善。本文研究了包裹在绝缘的聚甲基丙烯酸甲酯（PMMA）基质中并被热蒸发的金电极覆盖的聚合物包裹的单壁碳纳米管（SWNT）膜，作为复合空穴传输层和光学隔离层。利用瞬态吸收光谱，我们显示出SWNTs增强了从CQD到CQD，ZnO或SWNT的电荷转移速率。为了查明改进的基本机制，我们使用开尔文探针和循环伏安法通过测量带边缘的相对对准来研究结的能量学。通过测量外部量子效率和吸收率，我们发现改善主要不是电子方面的改善，而是CQD吸收体吸收的增加。我们通过采用转移矩阵模型从实验和理论上证明，透明的PMMA基质充当光学间隔物，从而导致吸收层吸收增强。通过这些电子和光学增强功能，PbS CQD太阳能电池的效率从4.0％提高到6.0％。通过测量外部量子效率和吸收率，我们发现改善主要不是电子方面的改善，而是CQD吸收体吸收的增加。我们通过采用转移矩阵模型从实验和理论上证明，透明的PMMA基质充当光学间隔物，从而导致吸收层吸收增强。通过这些电子和光学增强功能，PbS CQD太阳能电池的效率从4.0％提高到6.0％。通过测量外部量子效率和吸收率，我们发现改善主要不是电子方面的改善，而是CQD吸收体吸收的增加。我们通过采用转移矩阵模型从实验和理论上证明，透明的PMMA基质充当光学间隔物，从而导致吸收层吸收增强。通过这些电子和光学增强功能，PbS CQD太阳能电池的效率从4.0％提高到6.0％。

更新日期：2018-11-08

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