Sequential deposition as a route for efficient counter electrodes in quantum dot sensitized solar cells

Abstract

9In this paper, we introduce the sequential deposition method for enhancing the 10 performance of nanocomposite counter electrodes (CEs) in quantum dot sensitized solar 11 cells (QDSCs). Here, various CEs are made by the deposition of CuS, PbS, and 12 CuS/PbS nanocomposite layers on an FTO (fluorine doped tin oxide) coated glass 13 substrate by simple successive ionic layer adsorption and reaction (SILAR) method. The 14 result indicates that efficiency of the cells with CuS/PbS CEs enhances by 2.65 % 15 compare with the bare CuS (0.99 %) or PbS (1.47 %) CEs. Also, no considerable 16 improvement is observed for PbS/CuS CEs (1.09 %), which indicates that the order of 17 PbS and CuS deposition is critical for efficiency enhancement. Here, efficiency of the 18 cells with CuS/Pbs CEs was demonstrated to be systematically enhanced by one by one 19 deposition of CuS and PbS layers (sequential deposition). Also, for the CdS/CdSe QD 20 sensitized cells and sequentially deposited CuS/PbS CEs, the cell performance of 3.58 % 21is obtained which is enhanced by more than three and two times compared with the 22 efficiency of the cells with CuS (0.99%) and PbS (1.47%) CEs, respectively. The fill 23 factor is obtained as 0.53 which is the maximum value for CuS/PbS CEs, to our 24 knowledge. Impedance spectroscopy (IS) is performed on the QDSCs in order to 25 2 understand the origin of the performance increment. Results indicate that the electron 26 transfer resistance is reduced in the case of sequentially deposited CEs, while the series 27 resistance is almost the same. This general study represents that sequential deposition 28 method could offer new opportunities for the simple fabrication of solution-processed 29CEs in order to make efficient QDSCs. 30

Graphene/CuS/PbS nanocomposite as an effective counter electrode for quantum dot sensitized solar cells

“…The second category of the cells was made by deposition of CuS/PbS/../CuS/PbS CEs [10]. Here CuS/PbS/.../CuS/PbS CEs were made by to 12 cycles of SILAR deposition in order to optimize the CE structure.…”

“…Currently solution processed semiconductor nanocrystals are promising for making low cost, large scale and efficient quantum dot solar cells [1][2][3][4][5][6][7][8][9][10].…”

“…Also most importantly is easy for sealing the cells without electrolyte leakage. Regarding the simple procedure of SILAR method, recently various nanocomposite cathode electrodes like CoS/CuS, CuS/PbS are developed and enhanced the catalytic performance of the bare CuS, PbS and CoS CEs [10,31,45]. In spite of the interesting properties of SILAR deposited CEs on FTO coated glass substrates, these cathode electrodes have a compact structure in comparison to the CEs which are made on metallic substrates.…”

“…In spite of the interesting properties of SILAR deposited CEs on FTO coated glass substrates, these cathode electrodes have a compact structure in comparison to the CEs which are made on metallic substrates. The compact structure of the CE limits the CE/electrolyte interface which consequently restricts the charge transfer at CE/electrolyte interface [10]. Restricted charge transfer at the CE/Electrolyte interface, accumulates space charges and therefore diminish the fill factor considerably [41,[46][47].…”

Efficient CdS/CdSe/ZnS quantum dot sensitized solar cells prepared by ZnS treatment from methanol solvent

“…In the past few years, various promising approaches have been introduced for efficiency enhancement in QDSCs. These approaches include making nanocomposite structures of the photoanode [13,14] or doping the photoanode [15,16]; new routes for sensitizing the photoanode by QDs like cosensitizing or sensitizing by core/shell structures [17][18]; introducing new counter electrodes [19,20]; optimizing the electrolyte composition and modifying the photoanode by post treatments like TiCl 4 [21], O 2 plasma [22], mercaptopropionic acid [23] and fluorine treatment [24], annealing the photoanode in air/Ar atmosphere [25], and deposition ZnS on QD sensitizers [26][27][28]. Among these modification methods, ZnS treatment is the most popular one which has been generally used in all QDSCs after pioneering report of Yang et al [26] and its modification by Toyoda et al in 2008 [27].…”