Full Length ArticleQuantum dot sensitized solar cells fabricated by means of a novelinorganic spinel nanoparticleElnaz Jalali-Moghadam, Zahra Shariatinia⇑Department of Chemistry, Amirkabir University of Technology (Tehran Polytechnic), P.O. Box: 15875-4413, Tehran, Irana r t i c l e i n f oArticle history:Received 3 January 2018Revised 29 January 2018Accepted 2 February 2018Available online 3 February 2018Keywords:Quantum dot sensitized solar cellsZn 0.5184 La 0.7859 Ce 0.3994 Al 1.0026 O 4nanoparticlesPhotoluminescence spectraElectrochemical impedance spectra (EIS)XPSa b s t r a c tA novel inorganic spinel compound with formula Zn 0.5184 La 0.7859 Ce 0.3994 Al 1.0026 O 4 (ZLCA) was synthesizedby the gel combustion method and its exact formula was approved by the XPS analysis. The TEM imageexhibited that the ZLCA NPs were very f i ne, spherical and slightly agglomerated particles with their par-ticle size changed in the range of ?5–20 nm. Then, several quantum dot-sensitized solar cells (QDSSCs)were fabricated using this new compound which was doped into the TiO 2 pastes of photoanodes and sub-sequently the CdS, CdS and ZnS layers were deposited on the ZLCA-doped TiO 2 layer by the SILAR and theCBD methods. Results indicated that the photovoltaic parameters of the optimized cell ( g = 3.50%, J SC =11.690 mA?cm ?2 ) were boosted compared with those of the reference cell which was free of ZLCA NPs ( g= 2.14%, J SC = 7.075 mA?cm ?2 ) indicating rather high improvements of approximately 64 and 65% in theeff i ciency and short-circuit current density, respectively. The UV–Vis absorption spectra of all nanocom-posite photoanodes revealed broad absorption bands between ?320 and 600 nm. The lowest intensity ofthe photoluminescence peak for the CdSe cell fabricated using 0.6%ZLCA suggested that it had the leastcharge recombination and the easiest electron transfer which was conf i rmed by the J-V and eff i ciencyresults. The Electrochemical impedance spectra (EIS) illustrated that the charge transfer resistances(R CT ) of cells were dropped by addition of the ZLCA into the TiO 2 compared with that of the cell madewithout using ZLCA NPs. The R CT resistance was 1900 X for pure TiO 2 but it was decreased to 81.6 Xin the optimized cell containing 0.6%wt of ZLCA. Thus, it could be decided that doping 0.6%wt ZLCAwas appropriate to attain suitable photocurrent eff i ciency for the QDSSCs because it was used in a min-imum quantity to accelerate the electron transport, decrease the recombination and increase the celleff i ciency.? 2018 Elsevier B.V. All rights reserved.1. IntroductionThe requirement to discover renewable energy sources is a nec-essary task in order to defeat the danger of global warming andemission of greenhouse gases [1–4]. The demand for clean, renew-able and low-cost energy by the human society has encouraged theresearches to f i nd ways for developing the solar cells [5–7].Inorganic semiconductors have been considered as ideal next-generation sensitizers because of their bandgap tunability by con-trolling the absorption coeff i cient and quantum-dot size. As well,quantum dots can produce more than two electrons from a singlephoton when be placed exposed to the sun radiation (multiple-carrier generation) [8].The power conversion eff i ciency of QDSSCs is lower than that ofdye sensitized solar cells (DSSCs) and this is predominantly as aresult of the narrow adsorption range of QDs, weak electron collec-tion by the TiO 2 from the QDs, charge recombination at the QD-electrolyte interface, recombination at the counter electrode-electrolyte interface and the diff i culty in deposition of a satisfac-tory large number of QDs on a mesoporous TiO 2 matrix to acquirea well-covered monolayer without aggregation/cluster formation[9]. Another possible reason is the utilization of an instable elec-trolyte in which metal chalcogenide undergoes severe degradation[10].Typically, the charge recombination takes place in the structureof solar cells at three possible interfaces including workingelectrode/electrolyte, quantum-dot-sensitizer/electrolyte, andtransparent-conducting oxide/electrolyte [11,12]. Therefore, con-trolling these interfaces is the key issue for increasing chargecollection eff i ciencies. Among different efforts to improve thephotovoltaic properties, the control of interface for reducing thecharge recombination and rising the light harvesting ability hasproven to be the most impressive investigations [13–15]. In thishttps://doi.org/10.1016/j.apsusc.2018.02.0220169-4332/? 2018 Elsevier B.V. All rights reserved.⇑ Corresponding author.E-mail address: shariati@aut.ac.ir (Z. Shariatinia).Applied Surface Science 441 (2018) 1–11Contents lists available at ScienceDirectApplied Surface Sciencejournal homepage: www.elsevier.com/locate/apsusc
