- Nano Express
- Open Access
In situ growth of CuInS2 nanocrystals on nanoporous TiO2 film for constructing inorganic/organic heterojunction solar cells
Nanoscale Research Letters volume 8, Article number: 354 (2013)
Inorganic/organic heterojunction solar cells (HSCs) have attracted increasing attention as a cost-effective alternative to conventional solar cells. This work presents an HSC by in situ growth of CuInS2( CIS) layer as the photoabsorption material on nanoporous TiO2 film with the use of poly(3-hexylthiophene) (P3HT) as hole-transport material. The in situ growth of CIS nanocrystals has been realized by solvothermally treating nanoporous TiO2 film in ethanol solution containing InCl3 · 4H2O, CuSO4 · 5H2O, and thioacetamide with a constant concentration ratio of 1:1:2. InCl3 concentration plays a significant role in controlling the surface morphology of CIS layer. When InCl3 concentration is 0.1 M, there is a layer of CIS flower-shaped superstructures on TiO2 film, and CIS superstructures are in fact composed of ultrathin nanoplates as ‘petals’ with plenty of nanopores. In addition, the nanopores of TiO2 film are filled by CIS nanocrystals, as confirmed using scanning electron microscopy image and by energy dispersive spectroscopy line scan analysis. Subsequently, HSC with a structure of FTO/TiO2/CIS/P3HT/PEDOT:PSS/Au has been fabricated, and it yields a power conversion efficiency of 1.4%. Further improvement of the efficiency can be expected by the optimization of the morphology and thickness of CIS layer and the device structure.
The quest and demand for clean and economical energy sources have increased interest in the development of various solar cells, such as Si solar cells, Cu(In,Ga)(S,Se)2 film solar cells[3–6], organic solar cells, and dye-sensitized solar cells (DSSCs)[8–12]. Among these solar cells, DSSCs have been currently attracting widespread scientific and technological interest due to their low cost and high efficiency[8–12]. The typical working principle of DSSCs is based on ultrafast electron injection from a photoexcited dye into the conduction band of TiO2 and subsequent dye regeneration and hole transportation to the counter electrode. The power conversion efficiency of DSSCs with organic solvent-based electrolyte has been reported to exceed 11%[9, 13, 14]. However, DSSCs still suffer from some problems, such as high cost of Ru-based dyes, leakage and/or evaporation from organic solvent-based electrolyte.
For reducing the cost, the use of inorganic semiconductor nanocrystals instead of Ru-based dyes in DSSCs has attracted an enormous interest[15–18]. Semiconductor nanocrystals as the sensitizers have many fascinating advantages, such as high extinction coefficients, large intrinsic dipole moments, and the tuned bandgap. In particular, semiconductor quantum dots have capability of producing multiple electron/hole pairs with a single photon through the impact ionization effect. For depositing semiconductor nanocrystals on TiO2 films, two typical approaches have been developed. The first and most common route is the in situ synthesis of the nanocrystals on TiO2 film, for example, by chemical bath deposition or by successive ionic layer adsorption and reaction (SILAR). This method provides high surface coverage, but the lack of capping agents leads to a broad size distribution and a higher density of surface defects of nanocrystals, which deteriorates solar cell performance. The second route is the assembly of already-synthesized nanocrystals to TiO2 substrates by direct adsorption or linker-assisted adsorption. This ex situ approach could achieve better control over the sizes and electronic properties of nanocrystals but suffers from low surface coverage and poor electronic coupling. Up to now, many different semiconductor nanocrystals as the sensitizers have been investigated, including CdSe[17, 22, 25], CdS[21, 26], and PbS[27–29]. Unfortunately, these metal chalcogenide semiconductors are easily oxidized when exposed to light, and this unfavorable situation is even more detrimental when the metal sulfide is in contact with a liquid electrolyte containing sulfur. It is well known that the choice of semiconductors and the method of their deposition play a paramount role in affecting cell efficiency. Therefore, it is still necessary to develop new materials and deposition methods for improving DSSCs with semiconductors as the sensitizers.
On the other hand, for avoiding the sealing problem in DSSCs, many attempts have been made to substitute liquid electrolytes with quasi-solid electrolytes or solid-state hole transporting material (HTM). Similarly, when semiconductor nanocrystals are used as the sensitizers, some HTMs including poly(3-hexylthiophene) (P3HT) have been developed, resulting in the construction of all-solid-state inorganic/organic heterojunction solar cells (HSCs)[32–36], which possesses the advantages of both DSSCs and traditional organic solar cells. In particular, the efficiency of HSCs with the structure of TiO2/Sb2S3/P3HT has reached 5%, which is very close to the efficiencies reported for solid DSSCs using Ru-based molecular dyes. In addition, Sb2S3 nanocrystals are non-toxic compared with Cd/Pb-based semiconductors. These facts show the great potentiality of all-solid HSCs, which also encourages to further achieve other kind of robust, efficient, and cheap HSCs without toxic component.
Copper indium disulfide (CuInS2, abbreviated as CIS) has a small direct bandgap of 1.5 eV that matches well the solar spectrum, a large absorption coefficient (α = 5 × 105 cm−1), and low toxicity. It has been regarded to be a promising light-absorbing material for film solar cells. As semiconductor sensitizers in DSSCs, CIS nanocrystals have been prepared by different methods and then were coated/adsorbed on TiO2 film to construct DSSCs with liquid electrolyte[24, 37, 38]. In addition, the in situ growth of CIS on TiO2 film has also been realized, by electrodeposition, spin-coating/anneal, and SILAR method, to construct DSSCs with liquid electrolyte. However, there is little report on solvothermal growth of CIS nanocrystals on TiO2 film for the construction of all-solid HSCs. In this paper, we report a facile one-step solvothermal route for the in situ growth CIS nanocrystals on nanoporous TiO2 film. The effects of reagent concentration on the surface morphology of CIS have been investigated. The all-solid HSC with the structure of FTO/compact-TiO2 /nanoporous-TiO2/CIS/P3HT/PEDOT:PSS/Au is fabricated, and it exhibits a relatively high conversion efficiency of 1.4%.
All of the chemicals were commercially available and were used without further purification. Titanium butoxide, petroleum ether, TiCl4, CuSO4 · 5H2O, InCl3 · 4H2O, thioacetamide, ethanol, methanol, and 1,2-dichlorobenzene were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). TiO2 (P25) was obtained from Degussa. Transparent conductive glass (F:SnO2, FTO) was purchased from Wuhan Geao Instruments Science & Technology Co., Ltd (Wuhan, Hubei, China). P3HT was bought from Guanghe Electronic Materials Co., Ltd. (Henan, China). The poly(3-4-ethylenedioxythiophene) doped with poly(4-stylenesulfonate) (PEDOT:PSS) solution (solvent, H2O; weight percentage, 1.3%) was obtained from Aldrich (St. Louis, MO, USA).
Preparation of compact and nanoporous TiO2 film
A part of FTO glass was chemically etched away in order to prevent direct contact between the two electrodes. A compact (about 100-nm thick) TiO2 layer was first deposited onto the FTO glass as follow. FTO glass was dipped into the mixture of titanium butoxide and petroleum ether (2:98 V/V), taken out carefully, hydrolyzed in air for 30 min, and sintered in oven for 30 min at 450°C.
Then, nanoporous TiO2 films were prepared by the doctor-blading technique with TiO2 (P25) colloidal dispersion and subsequently sintered at 450°C for 30 min, according to a previous study. This film was soaked into a TiCl4 (20 mM in water) solution for 12 h. It was then washed with deionized water and ethanol, dried with air, and sintered again at 450°C for 30 min.
In situ solvothermal growth of CuInS2nanocrystals
CIS layer was in situ grown on nanoporous TiO2 films by a solvothermal process. In a typical process, thioacetamide (0.24 mmol, 0.02 M) was added into a 12 mL ethanol solution containing InCl3 · 4H2O (0.01 M) and CuSO4 · 5H2O (0.01 M) under magnetic stirring, until a clear solution was formed. The resulting solution was transferred into a Teflon-lined stainless steel autoclave with 30-mL capacity. Subsequently, FTO/compact-TiO2/nanoporous-TiO2 film as the substrate was vertically immersed into the solution. Lastly, the autoclave was kept in a fan-forced oven at 160°C for 12 h. After air-cooling to room temperature, CIS film on non-conductive glass side was scraped off, while CIS film on nanoporous TiO2 film side was washed with deionized water and absolute ethanol successively, and dried in air. For comparison, the effects of InCl3 · 4H2O concentrations (0.01, 0.03, 0.1 M) on the morphologies CIS layer were investigated. The concentration ratio of InCl3 · 4H2O, CuSO4 · 5H2O, and thioacetamide was maintained constant (1:1:2) for all the cases.
Fabrication of all-solid HSC
The P3HT solution (10 mg/mL in 1,2-dichlorobenzene) was spin-coated onto TiO2/CIS with 3,000 rpm for 60 s. Then, in order to improve the contact between P3HT and gold, a PEDOT:PSS solution diluted with two volumes of methanol was introduced onto TiO2/CIS/P3HT layer by spin-coating at 2,000 rpm for 30 s. In order to form a hybrid heterojunction, the TiO2/CIS/P3HT/PEDOT:PSS layer was then annealed at 90°C for 30 min in a vacuum oven. Gold layer as the back contact was prepared by magnetron sputtering with a metal mask, giving an active area of 16 mm2 for each device. The resulting HSC has a structure of FTO/compact-TiO2/nanoporous-TiO2/CIS/P3HT/PEDOT:PSS/Au.
Characterization and photoelectrical measurements
The sizes and morphologies of the sample were investigated by field emission scanning electron microscopy (FE-SEM; S-4800, Hitachi, Chiyoda-ku, Japan). During SEM measurement, energy dispersive spectroscopy (EDS; Quantax 400, Bruker AXS, Inc., Madison, WI, USA) line scan was also performed to locate and determine the distribution of different layer in the composite film. The X-ray diffraction (XRD; D/max-g B, Rigaku, Shibuya-ku, Japan) measurement was carried out using a Cu Kα radiation source (λ = 1.5418 Å). An ultraviolet/visible (UV-vis) spectrophotometer (U-3010 spectrophotometer, Hitachi, Chiyoda-ku, Japan) was used to carry out the optical measurements. The photocurrent density/voltage curves of HSC was measured under illumination (100 mW cm−2) using a computerized Keithley Model 2400 Source Meter unit (Keithley Instruments Inc., Cleveland, OH, USA) and a 300-W xenon lamp (Newport 69911, Newport-Oriel Instruments, Stratford, CT, USA) serving as the light source.
Results and discussion
Herein, the fabrication of all-solid HSC with the structure of FTO/compact-TiO2 /nanoporous-TiO2/CIS/P3HT/PEDOT:PSS/Au involved five steps, as demonstrated in Figure 1. The first step was to prepare a compact TiO2 layer by a dip-coating-anneal process (Figures 1 (step A) and 2), according our previous study. SEM images (Figure 2) confirm the formation of a dense TiO2 layer on FTO glass, and this TiO2 layer has a thickness of about 300 nm. The presence of compact TiO2 layer can not only improve the ohmic contact but also avoid short circuiting and/or loss of current by forming a blocking layer between FTO and P3HT in the HSC.
The second step was to fabricate nanoporous TiO2 film on FTO/compact-TiO2 by a classic doctor-blading-anneal technique with TiO2 (P25) colloidal dispersion (Figures 1 (step B) and 3). Such nanoporous TiO2 film has a thickness of about 2 μm, as revealed by cross-sectional SEM image (Figure 3a). In addition, one can find that the surface of nanoporous TiO2 film is uniform and smooth without crack (Figure 3b). High-resolution SEM (Figure 3c) reveals the TiO2 film to be composed of a three-dimensional network of interconnected particles with an average size of approximately 30 nm. It also can be found that there are many nanopores in the TiO2 film, which facilitates to absorb dye and/or other semiconductor nanocrystals.
The third step was to in situ grow CIS nanocrystals on nanoporous TiO2 film by the classic solvothermal process (Figure 1C), where FTO/compact-TiO2/nanoporous-TiO2 film as the substrate was vertically immersed into the ethanol solution containing InCl3, CuSO4, and thioacetamide with constant concentration ratio (1:1:2) as the reactant, and the solution was solvothermally treated at 160°C for 12 h. It has been found that reactant concentrations play a significant role in the controlled growth of CIS films in our previous study. Thus, the effects of reactant concentration (such as InCl3 concentration: 0.01, 0.03, 0.1 M) on the surface morphologies of CIS layer were investigated by SEM observation. Figure 4 gives the typical morphologies of CIS films prepared with different InCl3 concentration. When InCl3 concentration is low (0.01 or 0.03 M), a large amount of high-ordered potato chip-shaped CIS nanosheet arrays are densely packed and uniformly covered over the entire surface of FTO/compact-TiO2/nanoporous-TiO2 film (Figure 4a,c), which is similar to the in situ growth of CIS on Cu foil. More detailed nanostructure about CIS film can be observed using high-magnification SEM images (Figure 4b,d), where individual CIS nanosheet displays a crooked shape with a thickness of approximately 10 nm and length of approximately 2 μm. These CIS potato chip-shaped nanosheets are assembled and intermeshed with each other, forming a continuous net-like flat film. It should be noted that CIS chips may be too big to separate efficiently electron/hole pairs in the application of HSCs. As InCl3 concentration increased to 0.1 M, CIS flower-shaped superstructures with an average diameter of 3 μm spread over the whole FTO/compact-TiO2/nanoporous-TiO2 film (Figure 4e). In fact, as shown in the SEM image with higher magnification (Figure 4f), CIS superstructures are composed of ultrathin nanoplates as ‘petals’ with an average thickness of approximately 10 nm and length of approximately 0.6 μm. These ‘petals’ were aligned perpendicularly to the spherical surface with clearly oriented layers, pointing toward a common center. In addition, many hierarchical nanopores could be found among spherical superstructures and also among their ‘petals,’ which would improve the physicochemical properties.
Subsequently, TiO2/CIS film samples were further characterized. To confirm the structure and composition of samples with CIS prepared with 0.03 or 0.1 M InCl3, their cross-sectional morphologies were investigated. Obviously, a new layer can be found on the nanoporous TiO2 film, and the pores in TiO2 film have been partly filled with some nanoparticles (Figure 5a,b). Since CIS flower-shaped superstructure prepared from 0.1 M InCl3 is composed of ultrathin nanoplates as ‘petals’ and should be more suitable for HSC, we further analyzed the microstructure and local atomic composition of this film sample. Figure 5c shows the high-magnification SEM image in the middle of the cross section. Obviously, there are two kinds of nanoparticles. One has the relatively large diameter of about 20 to 50 nm, and it should be TiO2 nanoparticles, according to the SEM image (Figure 3c) of TiO2 film substrate. The other has the relatively small diameter of about 10 nm, and it should be CIS nanoparticles which were filled into the pores of TiO2 films. Furthermore, the red arrow on the SEM image shown in Figure 5b indicates the scanning path of an electron beam, and a clear presentation of the elemental distribution is given by a plot of the EDS line scan signal versus the distance along the film (Figure 6). Overall, EDS line scan profile shows that the signal peaks of the Cu, In, and S elements locate at the first region, indicating the presence of CIS. Subsequently, all signals from Cu, In, and S elements exhibit an obvious drop and then a fairly flat upon further increase of scanning distance in the middle region. On the contrary, in this middle region, the signal from Ti and O elements increase rapidly and then exhibit a fairly flat upon further increase of scanning distance. The clear distinct difference in the spatial profiles from CIS and TiO2 is well consistent with well-defined structures and SEM images, confirming that there is a CIS layer on the top of TiO2 film, and the pores of TiO2 film have been filled by CIS nanoparticles.
Furthermore, the phase and optical property of TiO2/CIS film sample with CIS prepared with 0.1 M InCl3 were investigated. Figure 7 shows the typical XRD pattern. Besides those existing peaks from SnO2 (2θ: 26.6°, 33.8°, 37.8°, 51.7°, 61.8°, 65.8°; from FTO substrate) and TiO2 film (2θ: 25.3°, 37.8°, 48.0°), the diffraction peaks at 27.8°, 46.5°, and 55.1° are assigned to (112), (204)/(220), and (312)/(116) planes of CIS, respectively, which are consistent with our previous study and the data obtained from JCPDS card no. 85-1575. This fact confirms that CIS layer is well crystallized and has chalcopyrite structure. Furthermore, the optical absorption of TiO2/CIS film was measured using a UV-vis spectrometer, as shown in Figure 8 (line A). This spectrum presents strong adsorption within a broad range between 400 and 800 nm, which is the characteristic absorption of CIS and consistent with our previous study.
The fourth step was to in turn deposit P3HT and PEDOT:PSS layer on FTO/compact-TiO2/nanoporous-TiO2/CIS film by the spin-coating process (Figure 1 (step D)). After the coating of P3HT, the photoabsorption of the film increases obviously in the range of 400 to 700 nm, as shown in Figure 8 (line B), since P3HT solution exhibits a wide and strong absorption with peak at about 445 nm. This fact also indicates the efficient deposition of P3HT in/on TiO2/CIS film. It should be noted that there are plenty of macro-pores among superstructures, nanopores inside CIS flower-shaped superstructures, and nanopores in TiO2 film due to the insufficient filling. The hierarchical combination of smaller nanopores and larger macro-pores can be considered as transport paths. It can be expected that P3HT solution can easily enter the deep layer of FTO/compact-TiO2/nanoporous-TiO2/CIS film through the transport paths, when they are coated onto its surface during the spin-coating process. This should lead to better effects of wetting and pore-filling and thus better interfacial contact among P3HT, CIS, and TiO2, probably resulting in more efficient separation of photoinduced electron/hole pairs and thus higher photocurrent.
The last step was to prepare gold electrode with the thickness of 100 nm on the resulting film for completing the construction of HSC (Figure 1 (step E)). Photocurrent density/voltage characteristics of the resulted HSC are shown in Figure 9. The cell exhibits an open circuit voltage (Voc) of 0.573 V, a short-circuit current density (Jsc) of 4.36 mA/cm2, and a fill factor (FF) of 0.561, yielding an overall energy conversion efficiency (η) of 1.40%. This conversion efficiency has been greatly improved, compared with that (typically 0.1% to 1.0%) of TiO2/P3HT hybrid HSCs in the absence of dye or PCBM[44–47]. There are chiefly three reasons for the improvement. The first reason is the good band alignment among TiO2, CIS, and P3HT (the inset of Figure 9), resulting in the fact that exciton dissociation and charge transfer at the interface are energetically favorable. The second reason should be attributed to the strong photoabsorption of CIS and P3HT, as revealed in Figure 8, since the successful sensitization of TiO2 by CIS layer has been well demonstrated by the previous studies[24, 38, 40]. The last reason results from the good interfacial contact among P3HT, CIS, and TiO2 due to hierarchical pores in CIS and TiO2 layer, as demonstrated in Figures 4 and5. In addition, it should be noted that our cell efficiency (1.4%) is relatively low compared with that (3% to 5%) of HSC with the structure of TiO2/Sb2S3/P3HT[32, 36, 48, 49], which probably results from the large size of CIS, unoptimized cell structure, etc. Therefore, further improvement of the efficiency could be expected by the optimization of the morphology and thickness of CIS layer and the device structure.
In summary, an in situ growth of CIS nanocrystals has been demonstrated by solvothermally treating nanoporous TiO2 film in ethanol solution containing InCl3 · 4H2O, CuSO4 · 5H2O, and thioacetamide with a constant concentration ratio of 1:1:2. When InCl3 concentration is 0.1 M, there is a CIS layer on the top of TiO2 film, and the pores of TiO2 film have been filled by CIS nanoparticles. An HSC with the structure of FTO/TiO2/CIS/P3HT/PEDOT:PSS/Au has been fabricated, and it yields a power conversion efficiency of 1.4%. Further improvement can be expected by optimizing CIS layer and the cell structure.
Gratzel M: Photoelectrochemical cells. Nature 2001, 414: 338–344. 10.1038/35104607
Peng KQ, Wang X, Li L, Wu XL, Lee ST: High-performance silicon nanohole solar cells. J Am Chem Soc 2010, 132: 6872–6873. 10.1021/ja910082y
Jackson P, Hariskos D, Lotter E, Paetel S, Wuerz R, Menner R, Wischmann W, Powalla M: New world record efficiency for Cu (In, Ga)Se2 thin-film solar cells beyond 20%. Prog Photovolt Res Appl 2011, 19: 894–897. 10.1002/pip.1078
Tang M, Tian Q, Hu X, Peng Y, Xue Y, Chen Z, Yang J, Xu X, Hu J: In situ preparation of CuInS2 films on a flexible copper foil and their application in thin film solar cells. Cryst Eng Comm 2012, 14: 1825–1832. 10.1039/c1ce05756a
Zhang L, Song L, Tian Q, Kuang X, Hu J, Liu J, Yang J, Chen Z: Flexible fiber-shaped CuInSe2 solar cells with single-wire-structure: design, construction and performance. Nano Energy 2012, 1: 769–776. 10.1016/j.nanoen.2012.07.022
Reddy VR, Wu J, Manasreh MO: Colloidal Cu(In x Ga1−x)Se2 nanocrystals for all-inorganic nano-heterojunction solar cells. Mater Lett 2013, 92: 296–299.
Lee K, Kim JY, Coates NE, Moses D, Nguyen TQ, Dante M, Heeger AJ: Efficient tandem polymer solar cells fabricated by all-solution processing. Science 2007, 317: 222–225. 10.1126/science.1141711
Oregan B, Gratzel M: A low-cost, high-efficiency solar-cell based on dye-sensitized colloidal TiO2 films. Nature 1991, 353: 737–740. 10.1038/353737a0
Gratzel M: Conversion of sunlight to electric power by nanocrystalline dye-sensitized solar cells. J Photoch Photobio A 2004, 164: 3–14. 10.1016/j.jphotochem.2004.02.023
Chen ZG, Li FY, Huang CH: Organic d-pi-a dyes for dye-sensitized solar cell. Curr Org Chem 2007, 11: 1241–1258. 10.2174/138527207781696008
Chen ZG, Li FY, Yang H, Yi T, Huang CH: A thermostable and long-term-stable ionic-liquid-based gel electrolyte for efficient dye-sensitized solar cells. Chem Phys Chem 2007, 8: 1293–1297. 10.1002/cphc.200700116
Hagfeldt A, Boschloo G, Sun L, Kloo L, Pettersson H: Dye-sensitized solar cells. Chem Rev 2010, 110: 6595–6663. 10.1021/cr900356p
Chen C-Y, Wang M, Li J-Y, Pootrakulchote N, Alibabaei L, C-h N-l, Decoppet J-D, Tsai J-H, Graetzel C, Wu C-G, Zakeeruddin SM, Grätzel M: Highly efficient light-harvesting ruthenium sensitizer for thin-film dye-sensitized solar cells. ACS Nano 2009, 3: 3103–3109. 10.1021/nn900756s
Yella A, Lee H-W, Tsao HN, Yi C, Chandiran AK, Nazeeruddin MK, Diau EW-G, Yeh C-Y, Zakeeruddin SM, Graetzel M: Porphyrin-sensitized solar cells with cobalt (II/III)-based redox electrolyte exceed 12 percent efficiency. Science 2011, 334: 629–634. 10.1126/science.1209688
Robel I, Subramanian V, Kuno M, Kamat PV: Quantum dot solar cells. Harvesting light energy with CdSe nanocrystals molecularly linked to mesoscopic TiO2 films. J Am Chem Soc 2006, 128: 2385–2393. 10.1021/ja056494n
Yun JH, Ng YH, Huang SJ, Conibeer G, Amal R: Wrapping the walls of n-TiO2 nanotubes with p-CuInS2 nanoparticles using pulsed-electrodeposition for improved heterojunction photoelectrodes. Chem Commun 2011, 47: 11288–11290. 10.1039/c1cc13738g
Choi H, Santra PK, Kamat PV: Synchronized energy and electron transfer processes in covalently linked CdSe-squaraine dye-TiO light harvesting assembly. ACS Nano 2012, 6: 5718–5726. 10.1021/nn301982e
Santra PK, Kamat PV: Tandem-layered quantum dot solar cells: tuning the photovoltaic response with luminescent ternary cadmium chalcogenides. J Am Chem Soc 2013, 135: 877–885. 10.1021/ja310737m
Alivisatos AP: Semiconductor clusters, nanocrystals, and quantum dots. Science 1996, 271: 933–937. 10.1126/science.271.5251.933
Nozik AJ: Exciton multiplication and relaxation dynamics in quantum dots: applications to ultrahigh-efficiency solar photon conversion. Inorg Chem 2005, 44: 6893–6899. 10.1021/ic0508425
Yan KY, Chen W, Yang SH: Significantly enhanced open circuit voltage and fill factor of quantum dot sensitized solar cells by linker seeding chemical bath deposition. J Phys Chem C 2013, 117: 92–99. 10.1021/jp3094319
Lee H, Wang MK, Chen P, Gamelin DR, Zakeeruddin SM, Gratzel M, Nazeeruddin MK: Efficient CdSe quantum dot-sensitized solar cells prepared by an improved successive ionic layer adsorption and reaction process. Nano Lett 2009, 9: 4221–4227. 10.1021/nl902438d
Mora-Sero I, Gimenez S, Fabregat-Santiago F, Gomez R, Shen Q, Toyoda T, Bisquert J: Recombination in quantum dot sensitized solar cells. Accounts Chem Res 2009, 42: 1848–1857. 10.1021/ar900134d
Li TL, Teng HS: Solution synthesis of high-quality CuInS2 quantum dots as sensitizers for TiO2 photoelectrodes. J Mater Chem 2010, 20: 3656–3664. 10.1039/b927279h
Yu Y, Kamat PV, Kuno M: A CdSe nanowire/quantum dot hybrid architecture for improving solar cell performance. Adv Funct Mater 2010, 20: 1464–1472. 10.1002/adfm.200902372
Chen C, Ali G, Yoo SH, Kum JM, Cho SO: Improved conversion efficiency of CdS quantum dot-sensitized TiO2 nanotube-arrays using CuInS2 as a co-sensitizer and an energy barrier layer. J Mater Chem 2011, 21: 16430–16435. 10.1039/c1jm13616j
Etgar L, Park J, Barolo C, Nazeeruddin MK, Viscardi G, Graetzel M: Design and development of novel linker for PbS quantum dots/TiO2 mesoscopic solar cell. ACS Appl Mater Inter 2011, 3: 3264–3267. 10.1021/am200811c
Benehkohal NP, Gonzalez-Pedro V, Boix PP, Chavhan S, Tena-Zaera R, Demopoulos GP, Mora-Sero I: Colloidal PbS and PbSeS quantum dot sensitized solar cells prepared by electrophoretic deposition. J Phys Chem C 2012, 116: 16391–16397. 10.1021/jp3056009
Etgar L, Moehl T, Gabriel S, Hickey SG, Eychmueller A, Graetzel M: Light energy conversion by mesoscopic PbS quantum dots/TiO2 heterojunction solar cells. ACS Nano 2012, 6: 3092–3099. 10.1021/nn2048153
Chen ZG, Yang H, Li XH, Li FY, Yi T, Huang CH: Thermostable succinonitrile-based gel electrolyte for efficient, long-life dye-sensitized solar cells. J Mater Chem 2007, 17: 1602–1607. 10.1039/b615915j
Bach U, Lupo D, Comte P, Moser JE, Weissortel F, Salbeck J, Spreitzer H, Gratzel M: Solid-state dye-sensitized mesoporous TiO2 solar cells with high photon-to-electron conversion efficiencies. Nature 1998, 395: 583–585. 10.1038/26936
Chang JA, Rhee JH, Im SH, Lee YH, Kim H-J, Seok SI, Nazeeruddin MK, Gratzel M: High-performance nanostructured inorganic–organic heterojunction solar cells. Nano Lett 2010, 10: 2609–2612. 10.1021/nl101322h
Balis N, Dracopoulos V, Stathatos E, Boukos N, Lianos P: A solid-state hybrid solar cell made of nc-TiO2, CdS quantum dots, and P3HT with 2-amino-1-methylbenzimidazole as an interface modifier. J Phys Chem C 2011, 115: 10911–10916.
Qian J, Liu Q-S, Li G, Jiang K-J, Yang L-M, Song Y: P3HT as hole transport material and assistant light absorber in CdS quantum dots-sensitized solid-state solar cells. Chem Commun 2011, 47: 6461–6463. 10.1039/c1cc11595b
Liu CP, Wang HE, Ng TW, Chen ZH, Zhang WF, Yan C, Tang YB, Bello I, Martinu L, Zhang WJ, Jha SK: Hybrid photovoltaic cells based on ZnO/Sb2S3/P3HT heterojunctions. Phys Status Solidi B 2012, 249: 627–633. 10.1002/pssb.201147393
Heo JH, Im SH, Kim H-J, Boix PP, Lee SJ, Seok SI, Mora-Sero I, Bisquert J: Sb2S3-sensitized photoelectrochemical cells: open circuit voltage enhancement through the introduction of poly-3-hexylthiophene interlayer. J Phys Chem C 2012, 116: 20717–20721. 10.1021/jp305150s
Li TL, Lee YL, Teng H: High-performance quantum dot-sensitized solar cells based on sensitization with CuInS2 quantum dots/CdS heterostructure. Energ Environ Sci 2012, 5: 5315–5324. 10.1039/c1ee02253a
Santra PK, Nair PV, Thomas KG, Kamat PV: CuInS2-sensitized quantum dot solar cell. Electrophoretic deposition, excited-state dynamics, and photovoltaic performance. J Phys Chem Lett 2013, 4: 722–729. 10.1021/jz400181m
Zhou ZJ, Fan JQ, Wang X, Sun WZ, Zhou WH, Du ZL, Wu SX: Solution fabrication and photoelectrical properties of CuInS2 nanocrystals on TiO2 nanorod array. ACS Appl Mater Inter 2011, 3: 2189–2194. 10.1021/am200500k
Zhou ZJ, Yuan SJ, Fan JQ, Hou ZL, Zhou WH, Du ZL, Wu SX: CuInS2 quantum dot-sensitized TiO2 nanorod array photoelectrodes: synthesis and performance optimization. Nanoscale Res Lett 2012, 7: 652. 10.1186/1556-276X-7-652
Chen ZG, Tang YW, Yang H, Xia YY, Li FY, Yi T, Huang CH: Nanocrystalline TiO2 film with textural channels: exhibiting enhanced performance in quasi-solid/solid-state dye-sensitized solar cells. J Power Sources 2007, 171: 990–998. 10.1016/j.jpowsour.2007.07.007
Nazeeruddin MK, Kay A, Rodicio I, Humphrybaker R, Muller E, Liska P, Vlachopoulos N, Gratzel M: Conversion of light to electricity by cis-x2bis(2,2′-bipyridyl-4,4′-dicarboxylate)ruthenium(ii) charge-transfer sensitizers (x = cl-, br-, i-, cn-, and scn-) on nanocrystalline TiO2 electrodes. J Am Chem Soc 1993, 115: 6382–6390. 10.1021/ja00067a063
Peng Y, Song G, Hu X, He G, Chen Z, Xu X, Hu J: In situ synthesis of P3HT-capped CdSe superstructures and their application in solar cells. Nanoscale Res Lett 2013, 8: 106. 10.1186/1556-276X-8-106
Chuang C-H, Lin Y-Y, Tseng Y-H, Chu T-H, Lin C-C, Su W-F, Chen C-W: Nanoscale morphology control of polymer/TiO2 nanocrystal hybrids: photophysics, charge generation, charge transport, and photovoltaic properties. J Phys Chem C 2010, 114: 18717–18724. 10.1021/jp1075516
Gerein NJ, Fleischauer MD, Brett MJ: Effect of TiO2 film porosity and thermal processing on TiO2-P3HT hybrid materials and photovoltaic device performance. Sol Energ Mat Sol Cells 2010, 94: 2343–2350. 10.1016/j.solmat.2010.08.010
Zeng T-W, Ho C-C, Tu Y-C, Tu G-Y, Wang L-Y, Su W-F: Correlating interface heterostructure, charge recombination, and device efficiency of poly(3-hexyl thiophene)/TiO2 nanorod solar cell. Langmuir 2011, 27: 15255–15260. 10.1021/la203533u
Tu Y-C, Lin J-F, Lin W-C, Liu C-P, Shyue J-J, Su W-F: Improving the electron mobility of TiO2 nanorods for enhanced efficiency of a polymer-nanoparticle solar cell. Cryst Eng Comm 2012, 14: 4772–4776. 10.1039/c2ce25489a
Im SH, Kim HJ, Rhee JH, Lim CS, Sang SI: Performance improvement of Sb2S3-sensitized solar cell by introducing hole buffer layer in cobalt complex electrolyte. Energ Environ Sci 2011, 4: 2799–2802. 10.1039/c0ee00741b
Cardoso JC, Grimes CA, Feng XJ, Zhang XY, Komarneni S, Zanoni MVB, Bao NZ: Fabrication of coaxial TiO2/Sb2S3 nanowire hybrids for efficient nanostructured organic-inorganic thin film photovoltaics. Chem Commun 2012, 48: 2818–2820. 10.1039/c2cc17573h
This work was financially supported by the National Natural Science Foundation of China (grant nos. 21107013, 21171035, and 51272299), Specialized Research Fund for the Doctoral Program of Higher Education (grant no. 20110075120012), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, projects of the Shanghai Committee of Science and Technology (grant nos. 10JC1400100, 13JC1400300), Innovation Program of Shanghai Municipal Education Commission (grant no. 13ZZ053), the Fundamental Research Funds for the Central Universities, the Shanghai Leading Academic Discipline Project (grant no. B603), and the Program of Introducing Talents of Discipline to Universities (grant no. 111-2-04).
The authors declare that they have no competing interests.
ZC designed the experiment and wrote the article. ZC, MT, and LS carried out the laboratory experiments. GT, BZ, LZ, JY, and JH assisted the technical support for measurements (SEM, EDS, XRD, UV–vis/NIR absorption, and I-V) as well as the data analysis. All authors read and approved the final manuscript.
Authors’ original submitted files for images
Below are the links to the authors’ original submitted files for images.
About this article
Cite this article
Chen, Z., Tang, M., Song, L. et al. In situ growth of CuInS2 nanocrystals on nanoporous TiO2 film for constructing inorganic/organic heterojunction solar cells. Nanoscale Res Lett 8, 354 (2013). https://doi.org/10.1186/1556-276X-8-354
- CuInS2 film
- In situ growth
- Heterojunction solar cells