Improving the Performance of PbS Quantum Dot Solar Cells by Optimizing ZnO Window Layer
Corresponding Author: Chun Cheng
Nano-Micro Letters,
Vol. 9 No. 2 (2017), Article Number: 24
Abstract
Comparing with hot researches in absorber layer, window layer has attracted less attention in PbS quantum dot solar cells (QD SCs). Actually, the window layer plays a key role in exciton separation, charge drifting, and so on. Herein, ZnO window layer was systematically investigated for its roles in QD SCs performance. The physical mechanism of improved performance was also explored. It was found that the optimized ZnO films with appropriate thickness and doping concentration can balance the optical and electrical properties, and its energy band align well with the absorber layer for efficient charge extraction. Further characterizations demonstrated that the window layer optimization can help to reduce the surface defects, improve the heterojunction quality, as well as extend the depletion width. Compared with the control devices, the optimized devices have obtained an efficiency of 6.7% with an enhanced V oc of 18%, J sc of 21%, FF of 10%, and power conversion efficiency of 58%. The present work suggests a useful strategy to improve the device performance by optimizing the window layer besides the absorber layer.
Highlights:
1 The efficiencies of PbS solar cells was significantly improved from 4.3% to 6.7% by optimizing ZnO window layer.
2 Optimized ZnO window layer can reduce the surface defects, extend thedepleted-heterojunction width and align with energy band of absorber layer.
Keywords
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- O.E. Semonin, J.M. Luther, S. Choi, H.-Y. Chen, J. Gao, A.J. Nozik, M.C. Beard, Peak external photocurrent quantum efficiency exceeding 100% via MEG in a quantum dot solar cell. Science 334(6062), 1530–1533 (2011). doi:10.1126/science.1209845
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References
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C.H.M. Chuang, P.R. Brown, V. Bulovic, M.G. Bawendi, Improved performance and stability in quantum dot solar cells through band alignment engineering. Nat. Mater. 13(8), 796–801 (2014). doi:10.1038/nmat3984
S.A. McDonald, G. Konstantatos, S. Zhang, P.W. Cyr, E.J.D. Klem, L. Levina, E.H. Sargent, Solution-processed PbS quantum dot infrared photodetectors and photovoltaics. Nat. Mater. 4(2), 138–142 (2005). doi:10.1038/nmat1299
G. Konstantatos, E.H. Sargent, PbS colloidal quantum dot photoconductive photodetectors: transport, traps, and gain. Appl. Phys. Lett. 91(17), 173505 (2007). doi:10.1063/1.2800805
K. Qiao, H. Deng, X. Yang, D. Dong, M. Li, L. Hu, H. Liu, H. Song, J. Tang, Spectra-selective PbS quantum dot infrared photodetectors. Nanoscale 8(13), 7137–7143 (2016). doi:10.1039/C5NR09069E
G. Konstantatos, C. Huang, L. Levina, Z. Lu, E.H. Sargent, Efficient infrared electroluminescent devices using solution-processed colloidal quantum dots. Adv. Funct. Mater. 15(11), 1865–1869 (2005). doi:10.1002/adfm.200500379
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H. Lee, H.C. Leventis, S.-J. Moon, P. Chen, S. Ito et al., PbS and CdS quantum dot-sensitized solid-state solar cells: “old concepts, new results”. Adv. Funct. Mater. 19(17), 2735–2742 (2009). doi:10.1002/adfm.200900081
G.I. Koleilat, L. Levina, H. Shukla, S.H. Myrskog, S. Hinds, A.G. Pattantyus-Abraham, E.H. Sargent, Efficient, stable infrared photovoltaics based on solution-cast colloidal quantum dots. ACS Nano 2(5), 833–840 (2008). doi:10.1021/nn800093v
J. Tang, L. Brzozowski, D.A.R. Barkhouse, X. Wang, R. Debnath et al., Quantum dot photovoltaics in the extreme quantum confinement regime: the surface-chemical origins of exceptional air- and light-stability. ACS Nano 4(2), 869–878 (2010). doi:10.1021/nn901564q
X. Lan, O. Voznyy, A. Kiani, F.P. Garcia de Arquer, A.S. Abbas et al., Passivation using molecular halides increases quantum dot solar cell performance. Adv. Mater. 28(2), 299–304 (2016). doi:10.1002/adma.201503657
M. Liu, F.P. de Arquer, Y. Li, X. Lan, G.H. Kim et al., Double-sided junctions enable high-performance colloidal-quantum-dot photovoltaics. Adv. Mater. 28(21), 4142–4148 (2016). doi:10.1002/adma.201506213
C.H. Chuang, P.R. Brown, V. Bulovic, M.G. Bawendi, Improved performance and stability in quantum dot solar cells through band alignment engineering. Nat. Mater. 13(8), 796–801 (2014). doi:10.1038/nmat3984
J. Luo, X. Dai, S. Bai, Y. Jin, Z. Ye, X. Guo, Ligand exchange of colloidal ZnO nanocrystals from the high temperature and nonaqueous approach. Nano-Micro Lett. 5(4), 274–280 (2013). doi:10.1007/BF03353758
G.H. Kim, F.P. Garcia de Arquer, Y.J. Yoon, X. Lan, M. Liu et al., High-efficiency colloidal quantum dot photovoltaics via robust self-assembled monolayers. Nano Lett. 15(11), 7691–7696 (2015). doi:10.1021/acs.nanolett.5b03677
Z. Yang, A. Janmohamed, X. Lan, F.P. Garcia de Arquer, O. Voznyy et al., Colloidal quantum dot photovoltaics enhanced by perovskite shelling. Nano Lett. 15(11), 7539–7543 (2015). doi:10.1021/acs.nanolett.5b03271
S. Bai, Z. Wu, X. Xu, Y. Jin, B. Sun et al., Inverted organic solar cells based on aqueous processed ZnO interlayers at low temperature. Appl. Phys. Lett. 100(20), 203906 (2012). doi:10.1063/1.4719201
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J. You, C.-C. Chen, L. Dou, S. Murase, H.-S. Duan et al., Metal oxide nanoparticles as an electron-transport layer in high-performance and stable inverted polymer solar cells. Adv. Mater. 24(38), 5267–5272 (2012). doi:10.1002/adma.201201958
E.A. Manor, T. Katz, F.C. Tromholt, Krebs, Enhancing functionality of ZnO hole blocking layer in organic photovoltaics. Sol. Energy Mater. Sol. Cells 98, 491–493 (2012). doi:10.1016/j.solmat.2011.11.026
C.E. Small, S. Chen, J. Subbiah, C.M. Amb, S.-W. Tsang, T.-H. Lai, J.R. Reynolds, F. So, High-efficiency inverted dithienogermole-thienopyrrolodione- based polymer solar cells. Nat. Photon. 6(2), 115–120 (2012). doi:10.1038/nphoton.2011.317
L. Guo, S. Yang, C. Yang, P. Yu, J. Wang, W. Ge, G.K.L. Wong, Highly monodisperse polymer-capped ZnO nanoparticles: preparation and optical properties. Appl. Phys. Lett. 76(20), 2901–2903 (2000). doi:10.1063/1.126511
H. Zhang, R.C. Shallcross, N. Li, T. Stubhan, Y. Hou, W. Chen, T. Ameri, M. Turbiez, N.R. Armstrong, C.J. Brabec, Overcoming electrode-induced losses in organic solar cells by tailoring a quasi-ohmic contact to fullerenes via solution-processed alkali hydroxide layers. Adv. Energy Mater. 6(9), 1502195 (2016). doi:10.1002/aenm.201502195
B.R. Lee, E.D. Jung, Y.S. Nam, M. Jung, J.S. Park et al., Amine-based polar solvent treatment for highly efficient inverted polymer solar cells. Adv. Mater. 26(3), 494–500 (2014). doi:10.1002/adma.201302991
R. Azmi, H. Aqoma, W.T. Hadmojo, J.-M. Yun, S. Yoon, K. Kim, Y.R. Do, S.-H. Oh, S.-Y. Jang, Low-temperature-processed 9% colloidal quantum dot photovoltaic devices through interfacial management of p-n heterojunction. Adv. Energy Mater. 6(8), 1502146 (2016). doi:10.1002/aenm.201502146
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S. Kwon, K.-G. Lim, M. Shim, H.C. Moon, J. Park et al., Air-stable inverted structure of hybrid solar cells using a cesium-doped ZnO electron transport layer prepared by a sol–gel process. J. Mater. Chem. A 1(38), 11802–11808 (2013). doi:10.1039/c3ta12425h
B.S. Ong, C. Li, Y. Li, Y. Wu, R. Loutfy, Stable, solution-processed, high-mobility ZnO thin-film transistors. J. Am. Chem. Soc. 129(10), 2750–2751 (2007). doi:10.1021/ja068876e
B. Du Ahn, S.H. Oh, C.H. Lee, G.H. Kim, H.J. Kim, S.Y. Lee, Influence of thermal annealing ambient on Ga-doped ZnO thin films. J. Cryst. Growth 309(2), 128–133 (2007). doi:10.1016/j.jcrysgro.2007.09.014
L. Hu, D.-B. Li, L. Gao, H. Tan, C. Chen et al., Graphene doping improved device performance of ZnMgO/PbS colloidal quantum dot photovoltaics. Adv. Funct. Mater. 26(12), 1899–1907 (2016). doi:10.1002/adfm.201505043
Y.S. Wang, P.J. Thomas, P. O’Brien, Optical properties of ZnO nanocrystals doped with Cd, Mg, Mn, and Fe Ions. J. Phys. Chem. B 110(43), 21412–21415 (2006). doi:10.1021/jp0654415
H. Zeng, W. Cai, J. Hu, G. Duan, P. Liu, Y. Li, Violet photoluminescence from shell layer of Zn/ZnO core-shell nanoparticles induced by laser ablation. Appl. Phys. Lett. 88(17), 171910 (2006). doi:10.1063/1.2196051
P.K. Nayak, J. Bisquert, D. Cahen, Assessing possibilities and limits for solar cells. Adv. Mater. 23(25), 2870–2876 (2011). doi:10.1002/adma.201100877
R.C. Rai, Analysis of the Urbach tails in absorption spectra of undoped ZnO thin films. J. Appl. Phys. 113(15), 153508 (2013). doi:10.1063/1.4801900
G.T. Ramesh, R. Gopikrishnan, K. Zhang, P. Ravichandran, S. Baluchamy et al., Synthesis, characterization and biocompatibility studies of zinc oxide (ZnO) nanorods for biomedical application. Nano-Micro Lett. 2(1), 31–36 (2010). doi:10.1007/BF03353614
Y. Sun, J.H. Seo, C.J. Takacs, J. Seifter, A.J. Heeger, Inverted polymer solar cells integrated with a low-temperature-annealed sol-gel-derived ZnO Film as an electron transport layer. Adv. Mater. 23(14), 1679–1683 (2011). doi:10.1002/adma.201004301
D. Yang, B. Li, C. Hu, H. Deng, D. Dong, X. Yang, K. Qiao, S. Yuan, H. Song, Controllable growth orientation of SnS2 flakes for low-noise, high-photoswitching ratio, and ultrafast phototransistors. Adv. Opt. Mater. 4(3), 419–426 (2016). doi:10.1002/adom.201500506
S. Christoulakis, M. Suchea, E. Koudoumas, M. Katharakis, N. Katsarakis, G. Kiriakidis, Thickness influence on surface morphology and ozone sensing properties of nanostructured ZnO transparent thin films grown by PLD. Appl. Surf. Sci. 252(15), 5351–5354 (2006). doi:10.1016/j.apsusc.2005.12.071
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