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In the paper, the core-shell ZnSe quantum dots (QDs)-sensitized mesoporous La-doped nano-TiO2 thin film is prepared by a direct adsorption method. Photoelectron characteristics, photogenerated carriers transport mechanism, and microstructure of the QDs-sensitized nano-TiO2 thin film are probed via the stationary surface photovoltaic (SPV) and the transient photovoltaic technologies, supplemented by the Brunauer-Emmet-Teller adsorption isotherm technique, scanning electron microscope, Fourier transform infrared (FT-IR) absorption spectrum, and ultraviolet-visible (UV-VIS) absorption spectrum. The experimental results confirm that the surface of the nano-TiO2 film is covered with the ZnSe QDs with smaller particles by a chemical absorbing way, resulting in denser composite film of the QDs and the mesoporous nano-TiO2 than the nano-TiO2 film. In our experiment, the adsorption quantity of ZnSe QDs on nano-TiO2 film can be controlled effectively. The results show that ligand L-Cys capped at the outer layer of ZnSe QDs plays an important role in the sensitization process. Specifically, the peak of SH in the ligand disappears at 2552 cm-1 in the FT-IR spectrum of the ZnSe QDs capped by the ligand as a stabilizer. This indicates that the SH bond is broken. In the meantime, the peak of the CS stretching vibration in the ligand shifts from 638 cm-1 to 663 cm-1 due to the formation of ZnS bond. These imply that the core-shell ZnSe/ZnS/L-Cys QDs are obtained. On the other hand, according to the peak of COOH stretching vibration disappearing at 1600 cm-1 in the FT-IR spectrum of the core-shell QDs-sensitized mesoporous nano-TiO2 film, the unsaturated Ti atoms on the surface of the TiO2 film are bonded to carboxy groups from the ligand capped at the QDs. That is, the ligand acts as a bridge between the QDs and the nano-TiO2 film for achieving the sensitization. Some excellent photovoltaic characteristics of the composite film are found as follows. 1) The SPV responses of the QDs-sensitized film appear in a wavelength region of 300 nm to 800 nm (UV-VIS-Near-IR), causing the region of SPV response to enlarge about 200 nm over that of the ZnSe QDs, and 400 nm over that of the nano-TiO2 thin film. 2) The QDs-sensitized film displays an n-type photovoltaic characteristic that is different from that of the QDs. This may be more favorable for transferring those carriers from the film surface to the photo-anode material. 3) Both the separation rate and the diffusion length of photogenerated electron-hole pairs are obviously increased, and the lifetime of free charge carriers in the ZnSe QDs-sensitized film prolongs about an order of magnitude over that of the nano-TiO2 film and ZnSe QDs.
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Keywords:
- ZnSe QDs /
- nano-TiO2 /
- quantum dots-sensitized film /
- surface photovoltaic technology
[1] Grtzel M 2001 Nature 414 338
[2] Zaban A, Micic O I, Gregg B A, Nozik A J 1998 Langmuir 14 3153
[3] Gimenez S, Mora-Sero I, Macor L, Guijarro N, Lana-Villarreal T, Gomez R, Diguna L J, Shen Q, Toyoda T, Bisquert J 2009 Nanotechnology 20 295204
[4] Nozik A J 2002 Physica E 14 115
[5] Dai S Y, Kong F T, Hu L H, Shi C W, Fang X Q, Pan X, Wang K J 2005 Acta Phys. Sin. 54 1919 (in Chinese) [戴松元, 孔凡太, 胡林华, 史成武, 方霞琴, 潘旭, 王孔嘉 2005 物理学报 54 1919]
[6] Sun W T, Yu Y, Pan H Y, Gao X F, Chen Q, Peng L M 2008 J. Am. Chem. Soc. 130 1124
[7] Yu W W, Qu L H, Guo W Z, Peng X G 2003 Chem. Mater. 15 2854
[8] Nozik A J, Beard M C, Luther J M, Law M, Ellingson R J, Johnson J C 2010 Chem. Rev. 110 6873
[9] Robel I, Subramanian V, Kuno M, Kamat P V 2006 J. Am. Chem. Soc. 128 2385
[10] Nozik A J 2010 Nano Lett. 10 2735
[11] Schaller R D, Agranovich V M, Klimov V I 2005 Nat. Phys. 1 189
[12] Klimov V I 2006 J. Phys. Chem. B 110 16827
[13] Diguna L J, Shen Q, Kobayashi J, Toyoda T 2007 Appl. Phys. Lett. 91 023116
[14] Li L Q, Liu A P, Zhao H X, Cui C, Tang W H 2012 Acta Phys. Sin. 61 108201 (in Chinese) [李立群, 刘爱萍, 赵海新, 崔灿, 唐为华 2012 物理学报 61 108201]
[15] Tian J, Gao R, Zhang Q, Zhang S, Li Y, Lan J, Qu X, Cao G 2012 J. Phys. Chem. C 116 18655
[16] Hossain M A, Jennings J R, Shen C, Pan J H, Koh Z Y, Mathews N, Wang Q 2012 J. Mater. Chem. 22 16235
[17] Zhou Z, Yuan S, Fan J, Hou Z, Zhou W, Du Z, Wu S 2012 Nanoscale Res. Lett. 7 652
[18] Bang J H, Kamat P V 2010 Adv. Funct. Mater. 20 1970
[19] Huang S, Zhang Q, Huang X, Guo X, Deng M, Li D, Luo Y, Shen Q, Toyoda T, Meng Q 2010 Nanotechnology 21 375201
[20] Gao X F, Li H B, Sun W T, Chen Q, Tang F Q, Peng L M 2009 J. Phys. Chem. C 113 7531
[21] Li G S, Zhang D Q, Yu J C 2009 Environ. Sci. Technol. 43 7079
[22] Zhou Z J, Fan J Q, Wang X, Sun W Z, Zhou W H, Du Z L, Wu S X 2011 ACS Appl. Mater. Interfaces 3 2189
[23] Shen H, Jiao X, Oron D, Li J, Lin H 2013 J. Power Sources 240 8
[24] Shen X, Jia J, Lin Y, Zhou X 2015 J. Power Sources 277 215
[25] Lee H, Wang M, Chen P, Gamelin D R, Zakeeruddin S M, Gratzel M, Nazeeruddin M K 2009 Nano Lett. 9 4221
[26] Jumabekov A N, Siegler T D, Cordes N, Medina D D, Bhm D, Garbus P, Meroni S, Peter L M, Bein T 2014 J. Phys. Chem. C 118 25853
[27] Chang C H, Lee Y L 2007 Appl. Phys. Lett. 91 053503
[28] Nair P K, Nair M T S, Garcia V M, Arenas O L, Pena Y, Castillo A, Ayala I T, Gomezdaza O, Sanchez A, Campos J, Hu H, Suarez R, Rincon M E 1998 Sol. Energy Mater. Sol. Cells 52 313
[29] Li W J, Zhong X H 2015 Acta Phys. Sin. 64 038806 (in Chinese) [李文杰, 钟新华 2015 物理学报 64 038806]
[30] Mora-Sero I, Gimenez S, Moehl T, Fabregat-Santiago F, Lana-Villareal T, Gomez R, Bisquert J 2008 Nanotechnology 19 424007
[31] Zhu G, Pan L, Xu T, Sun Z 2011 ACS Appl. Mater. Interfaces 3 3146
[32] Ma X, Shen Y, Wu G, Wu Q, Pei B, Cao M, Gu F 2012 J. Alloys Compd. 538 61
[33] Yu X Y, Lei B X, Kuang D B, Su C Y 2011 Chem. Sci. 2 1396
[34] Song X, Wang M, Shi Y, Deng J, Yang Z, Yao X 2012 Electrochim. Acta 81 260
[35] Antonelli D M, Ying J Y 1995 Angew. Chem. Int. Ed. Engl. 34 2014
[36] Jing L Q, Sun X J, Xin B F, Wang B Q, Cai W M, Fu H G 2004 J. Solid State Chem. 177 3375
[37] Ding I K, Ttreault N, Brillet J, Hardin B E, Smith E H, Rosenthal S J, Sauvage F, Grtzel M, McGehee M D 2009 Adv. Funct. Mater. 19 2431
[38] Murase N, Gao M 2004 Mater. Lett. 58 3898
[39] Liu B T, Yu H Y, Wang Y, Peng L L, Han T, Tian L L, Yan L T 2015 J. Alloys Compd. 640 246
[40] Schroder D K 2002 Mater. Sci. Eng. 92 196
[41] Wei X, Xie T, Xu D, Zhao Q, Pang S, Wang D 2008 Nanotechnology 19 275707
[42] Nakade S, Saito Y, Kubo W, Kanzaki T, Kitamura T, Wada Y, Yanagida S 2004 J. Phys. Chem. B 108 1628
[43] Kronik L, Shapira Y 1999 Surf. Sci. Rep. 37 1
[44] Lowell S, Shields J E, Thomas M A, Thommes M 2004 Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density (Dordrecht: Kluwer Academic) pp20-22
[45] Li K Y, Liu T, Zhou B J, Wei S L, Yang W Y 2010 Acta Phys.-Chim. Sin. 26 403 (in Chinese) [李葵英, 刘通, 周冰晶, 魏赛玲, 杨伟勇 2010 物理化学学报 26 403]
[46] Li J G, Ishigaki T, Sun X D 2007 J. Phys. Chem. C 111 4969
[47] Tauc J, Menth A 1972 J. Non-Cryst. Solids 8 569
[48] Li K Y, Shan Q S, Zhu R P, Yin H, Lin Y Y, Wang L Q 2015 Nanoscale 7 7906
[49] Duzhko V, Koch F, Dittrich T 2002 J. Appl. Phys. 91 9432
[50] Zhang Q, Wang D, Wei X, Xie T, Li Z, Lin Y, Yang M 2005 Thin Solid Films 491 242
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[1] Grtzel M 2001 Nature 414 338
[2] Zaban A, Micic O I, Gregg B A, Nozik A J 1998 Langmuir 14 3153
[3] Gimenez S, Mora-Sero I, Macor L, Guijarro N, Lana-Villarreal T, Gomez R, Diguna L J, Shen Q, Toyoda T, Bisquert J 2009 Nanotechnology 20 295204
[4] Nozik A J 2002 Physica E 14 115
[5] Dai S Y, Kong F T, Hu L H, Shi C W, Fang X Q, Pan X, Wang K J 2005 Acta Phys. Sin. 54 1919 (in Chinese) [戴松元, 孔凡太, 胡林华, 史成武, 方霞琴, 潘旭, 王孔嘉 2005 物理学报 54 1919]
[6] Sun W T, Yu Y, Pan H Y, Gao X F, Chen Q, Peng L M 2008 J. Am. Chem. Soc. 130 1124
[7] Yu W W, Qu L H, Guo W Z, Peng X G 2003 Chem. Mater. 15 2854
[8] Nozik A J, Beard M C, Luther J M, Law M, Ellingson R J, Johnson J C 2010 Chem. Rev. 110 6873
[9] Robel I, Subramanian V, Kuno M, Kamat P V 2006 J. Am. Chem. Soc. 128 2385
[10] Nozik A J 2010 Nano Lett. 10 2735
[11] Schaller R D, Agranovich V M, Klimov V I 2005 Nat. Phys. 1 189
[12] Klimov V I 2006 J. Phys. Chem. B 110 16827
[13] Diguna L J, Shen Q, Kobayashi J, Toyoda T 2007 Appl. Phys. Lett. 91 023116
[14] Li L Q, Liu A P, Zhao H X, Cui C, Tang W H 2012 Acta Phys. Sin. 61 108201 (in Chinese) [李立群, 刘爱萍, 赵海新, 崔灿, 唐为华 2012 物理学报 61 108201]
[15] Tian J, Gao R, Zhang Q, Zhang S, Li Y, Lan J, Qu X, Cao G 2012 J. Phys. Chem. C 116 18655
[16] Hossain M A, Jennings J R, Shen C, Pan J H, Koh Z Y, Mathews N, Wang Q 2012 J. Mater. Chem. 22 16235
[17] Zhou Z, Yuan S, Fan J, Hou Z, Zhou W, Du Z, Wu S 2012 Nanoscale Res. Lett. 7 652
[18] Bang J H, Kamat P V 2010 Adv. Funct. Mater. 20 1970
[19] Huang S, Zhang Q, Huang X, Guo X, Deng M, Li D, Luo Y, Shen Q, Toyoda T, Meng Q 2010 Nanotechnology 21 375201
[20] Gao X F, Li H B, Sun W T, Chen Q, Tang F Q, Peng L M 2009 J. Phys. Chem. C 113 7531
[21] Li G S, Zhang D Q, Yu J C 2009 Environ. Sci. Technol. 43 7079
[22] Zhou Z J, Fan J Q, Wang X, Sun W Z, Zhou W H, Du Z L, Wu S X 2011 ACS Appl. Mater. Interfaces 3 2189
[23] Shen H, Jiao X, Oron D, Li J, Lin H 2013 J. Power Sources 240 8
[24] Shen X, Jia J, Lin Y, Zhou X 2015 J. Power Sources 277 215
[25] Lee H, Wang M, Chen P, Gamelin D R, Zakeeruddin S M, Gratzel M, Nazeeruddin M K 2009 Nano Lett. 9 4221
[26] Jumabekov A N, Siegler T D, Cordes N, Medina D D, Bhm D, Garbus P, Meroni S, Peter L M, Bein T 2014 J. Phys. Chem. C 118 25853
[27] Chang C H, Lee Y L 2007 Appl. Phys. Lett. 91 053503
[28] Nair P K, Nair M T S, Garcia V M, Arenas O L, Pena Y, Castillo A, Ayala I T, Gomezdaza O, Sanchez A, Campos J, Hu H, Suarez R, Rincon M E 1998 Sol. Energy Mater. Sol. Cells 52 313
[29] Li W J, Zhong X H 2015 Acta Phys. Sin. 64 038806 (in Chinese) [李文杰, 钟新华 2015 物理学报 64 038806]
[30] Mora-Sero I, Gimenez S, Moehl T, Fabregat-Santiago F, Lana-Villareal T, Gomez R, Bisquert J 2008 Nanotechnology 19 424007
[31] Zhu G, Pan L, Xu T, Sun Z 2011 ACS Appl. Mater. Interfaces 3 3146
[32] Ma X, Shen Y, Wu G, Wu Q, Pei B, Cao M, Gu F 2012 J. Alloys Compd. 538 61
[33] Yu X Y, Lei B X, Kuang D B, Su C Y 2011 Chem. Sci. 2 1396
[34] Song X, Wang M, Shi Y, Deng J, Yang Z, Yao X 2012 Electrochim. Acta 81 260
[35] Antonelli D M, Ying J Y 1995 Angew. Chem. Int. Ed. Engl. 34 2014
[36] Jing L Q, Sun X J, Xin B F, Wang B Q, Cai W M, Fu H G 2004 J. Solid State Chem. 177 3375
[37] Ding I K, Ttreault N, Brillet J, Hardin B E, Smith E H, Rosenthal S J, Sauvage F, Grtzel M, McGehee M D 2009 Adv. Funct. Mater. 19 2431
[38] Murase N, Gao M 2004 Mater. Lett. 58 3898
[39] Liu B T, Yu H Y, Wang Y, Peng L L, Han T, Tian L L, Yan L T 2015 J. Alloys Compd. 640 246
[40] Schroder D K 2002 Mater. Sci. Eng. 92 196
[41] Wei X, Xie T, Xu D, Zhao Q, Pang S, Wang D 2008 Nanotechnology 19 275707
[42] Nakade S, Saito Y, Kubo W, Kanzaki T, Kitamura T, Wada Y, Yanagida S 2004 J. Phys. Chem. B 108 1628
[43] Kronik L, Shapira Y 1999 Surf. Sci. Rep. 37 1
[44] Lowell S, Shields J E, Thomas M A, Thommes M 2004 Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density (Dordrecht: Kluwer Academic) pp20-22
[45] Li K Y, Liu T, Zhou B J, Wei S L, Yang W Y 2010 Acta Phys.-Chim. Sin. 26 403 (in Chinese) [李葵英, 刘通, 周冰晶, 魏赛玲, 杨伟勇 2010 物理化学学报 26 403]
[46] Li J G, Ishigaki T, Sun X D 2007 J. Phys. Chem. C 111 4969
[47] Tauc J, Menth A 1972 J. Non-Cryst. Solids 8 569
[48] Li K Y, Shan Q S, Zhu R P, Yin H, Lin Y Y, Wang L Q 2015 Nanoscale 7 7906
[49] Duzhko V, Koch F, Dittrich T 2002 J. Appl. Phys. 91 9432
[50] Zhang Q, Wang D, Wei X, Xie T, Li Z, Lin Y, Yang M 2005 Thin Solid Films 491 242
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