Grafting and co-grafting of dyes on Cd-doped ZnS nanocrystals and their application on dye-sensitized solar cells UZMA JABEEN 1,2 , SYED MUJTABA SHAH 2 , MUHAMMAD AAMIR 3, * and IQBAL AHMAD 4 1 Faculty of Basic Sciences, Sardar Bahadur Khan Women’s University, Quetta 87300, Pakistan 2 Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan 3 Materials Laboratory, Department of Chemistry, Mirpur University of Science and Technology (MUST), Mirpur 10250, Pakistan 4 Department of Chemistry, Allama Iqbal Open University, Islamabad 44000, Pakistan *Author for correspondence ([email protected]) MS received 18 June 2021; accepted 23 August 2021 Abstract. Herein, we report that an efficient nanohybrid material consists of Cd-doped ZnS nanocrystals (NCs), merocyanine and fullerene (C60-pyrrolidine tris acid). Cd-ZnS NCs serve as a substrate for supramolecular complexation between merocyanine 540 and fullerenes. The impact of grafting and co-grafting of dyes on the NCs surface was checked by Fourier transform infrared (FTIR), photoluminescence and ultraviolet–visible (UV–Vis) spectroscopic studies. Cd- doped ZnS NCs were synthesized by wet chemical approach and described by powdered X-ray diffraction, UV–Vis spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. The grafted and co- grafted NCs were then used as an active blend in hybrid solar cells. The hybrid solar cell of grafted material blend (Cd- ZnS-MC540) shows the maximum short circuit current density 4.60 mA cm –2 and power conversion efficiency of 0.83%. The open circuit voltage, fill factors and cell conversion efficiency of all photovoltaic devices based on co-grafted Cd- doped ZnS NCs and P3HT decreases with the increase in concentration of donor and acceptor species. We note that by co- grafting, dye/dye interaction is replaced by dye/fullerene interaction but unfortunately co-grafting may have led to the formation of big clusters. Hence, the lack of morphological homogeneity may be held responsible for the weak perfor- mance of the solar cells. Keywords. Zinc sulphide; merocyanine; grafting; co-grafting; dye-sensitized solar cell; short-circuit current density. 1. Introduction Substantial effort has been employed in past few decades to fabricate efficient renewable energy conversion devices [1]. Recently, a great attention has been paid on organic polymers and nanocrystals (NCs)-based devices like thin film transistors, lasers, light-emitting diodes and photo- voltaic devices due to their low cost, flexibility and simple processability [2–4]. Among photovoltaics, dye- sensitized solar cells (DSSCs) have gained enormous attention owing to cost effectiveness, easy processability and low toxicity [5–7]. In the field of photonics and artificial photosynthesis, the efficient electron transfers, long-lived charge separated states, and strong quantum yield by decelerating charge recombination and enhanced charge separation are the critical challenges [8,9]. In this perspective, transition metal polyperidyl complexes and organic dyes have been employed as a photosensitizer with considerable efficiency [10–12]. Organic dyes along with D-p-A structures, riveted to the semiconducting surface via carboxylic functionalities, have been estab- lished as efficient photosensitizers [13,14]. The fullerenes like C60 and its derivatives have been widely explored as an electron acceptor to fabricate efficient light harvesting devices with better charge separation [15,16]. Fullerenes are carrier acceptors owing to their photophysical and electrochemical characteristics, as they can accept up to six electrons in the three lowest unoccupied molecular orbitals and efficiently transfer electron to gen- erate a long-lived charge separated state along with strong quantum yield [17,18]. Provoked by the beyond funda- mental features of fullerenes, donor–acceptor charge transfer complex systems have shown distinctive inter and intramolecular interactions after photoexcitation [19]. MC540, an anionic cyanine dye, is a heterocyclic chro- mophore which is employed as a photosensitizer in chemotherapy, DSSCs and in photo-electrochemical devices [20]. Among various semiconducting nanostructures, zinc oxide (ZnO) nanorods have fascinated scientific community Bull. Mater. Sci. (2021) 44:291 Ó Indian Academy of Sciences https://doi.org/10.1007/s12034-021-02575-3
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Grafting and co-grafting of dyes on Cd-doped ZnS nanocrystalsand their application on dye-sensitized solar cells
UZMA JABEEN1,2, SYED MUJTABA SHAH2, MUHAMMAD AAMIR3,* and IQBAL AHMAD4
1 Faculty of Basic Sciences, Sardar Bahadur Khan Women’s University, Quetta 87300, Pakistan2 Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan3 Materials Laboratory, Department of Chemistry, Mirpur University of Science and Technology (MUST),
Mirpur 10250, Pakistan4 Department of Chemistry, Allama Iqbal Open University, Islamabad 44000, Pakistan
Abstract. Herein, we report that an efficient nanohybrid material consists of Cd-doped ZnS nanocrystals (NCs),
merocyanine and fullerene (C60-pyrrolidine tris acid). Cd-ZnS NCs serve as a substrate for supramolecular complexation
between merocyanine 540 and fullerenes. The impact of grafting and co-grafting of dyes on the NCs surface was checked
by Fourier transform infrared (FTIR), photoluminescence and ultraviolet–visible (UV–Vis) spectroscopic studies. Cd-
doped ZnS NCs were synthesized by wet chemical approach and described by powdered X-ray diffraction, UV–Vis
spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. The grafted and co-
grafted NCs were then used as an active blend in hybrid solar cells. The hybrid solar cell of grafted material blend (Cd-
ZnS-MC540) shows the maximum short circuit current density 4.60 mA cm–2 and power conversion efficiency of 0.83%.
The open circuit voltage, fill factors and cell conversion efficiency of all photovoltaic devices based on co-grafted Cd-
doped ZnS NCs and P3HT decreases with the increase in concentration of donor and acceptor species. We note that by co-
grafting, dye/dye interaction is replaced by dye/fullerene interaction but unfortunately co-grafting may have led to the
formation of big clusters. Hence, the lack of morphological homogeneity may be held responsible for the weak perfor-
mance of the solar cells.
Keywords. Zinc sulphide; merocyanine; grafting; co-grafting; dye-sensitized solar cell; short-circuit current density.
1. Introduction
Substantial effort has been employed in past few decades
to fabricate efficient renewable energy conversion devices
[1]. Recently, a great attention has been paid on organic
polymers and nanocrystals (NCs)-based devices like thin
film transistors, lasers, light-emitting diodes and photo-
voltaic devices due to their low cost, flexibility and
simple processability [2–4]. Among photovoltaics, dye-
sensitized solar cells (DSSCs) have gained enormous
attention owing to cost effectiveness, easy processability
and low toxicity [5–7]. In the field of photonics and
artificial photosynthesis, the efficient electron transfers,
long-lived charge separated states, and strong quantum
yield by decelerating charge recombination and enhanced
charge separation are the critical challenges [8,9]. In this
perspective, transition metal polyperidyl complexes and
organic dyes have been employed as a photosensitizer
with considerable efficiency [10–12]. Organic dyes along
with D-p-A structures, riveted to the semiconducting
surface via carboxylic functionalities, have been estab-
lished as efficient photosensitizers [13,14].
The fullerenes like C60 and its derivatives have been
widely explored as an electron acceptor to fabricate efficient
light harvesting devices with better charge separation
[15,16]. Fullerenes are carrier acceptors owing to their
photophysical and electrochemical characteristics, as they
can accept up to six electrons in the three lowest unoccupied
molecular orbitals and efficiently transfer electron to gen-
erate a long-lived charge separated state along with strong
quantum yield [17,18]. Provoked by the beyond funda-
mental features of fullerenes, donor–acceptor charge
transfer complex systems have shown distinctive inter and
intramolecular interactions after photoexcitation [19].
MC540, an anionic cyanine dye, is a heterocyclic chro-
mophore which is employed as a photosensitizer in
chemotherapy, DSSCs and in photo-electrochemical
devices [20].
Among various semiconducting nanostructures, zinc
oxide (ZnO) nanorods have fascinated scientific community
Bull. Mater. Sci. (2021) 44:291 � Indian Academy of Scienceshttps://doi.org/10.1007/s12034-021-02575-3Sadhana(0123456789().,-volV)FT3](0123456789().,-volV)
due to the surface functionalization with organic dyes,
which can be synthesized by means of appropriate length/
width characteristic fraction and correspond to best scaf-
folds to accumulate organic colour barrier on their surface.
The porphyrin molecules have been successfully grafted
onto the surface of zinc oxide [21–23]. Furthermore, zinc
oxide, as an electron acceptor can favour the charge sepa-
ration characteristics of the organic binary complex [24].
Likewise, zinc sulphide (ZnS) and cadmium sulphide (CdS)
have also been found promising semiconductors for pho-
tovoltaic applications [25].
In this study, we selected merocyanine 540 as a sensitizer
or donor species for Cd-ZnS NCs. In this context, Cd-ZnS
NCs were grafted with merocyanine 540 and fullerene
derivatives with a view to facilitate charge injection. The