Template Synthesis of CuInS₂ Nanocrystals from In₂S₃ Nanoplates and Their Application as Counter Electrodes in Dye-Sensitized Solar Cells

Abstract

We report the room temperature template synthesis of CuInS 2 nanocrystals through incorporation of Cu + cations into In 2 S 3 nanoplates whose chemical composition has been controlled by varying the amount of copper ions in the reaction mixture. As a result, bandgaps of the resultant CuInS 2 nanoplates can be tuned from 1.45 to 1.19 eV with [Cu]/[In] molar ratios increasing from 0.7 to 2.9, which was demonstrated by the cyclic voltammetry. We explored the use of CuInS 2 nanocrystals as potential counter electrode in dye-sensitized solar cells and a power conversion efficiency of 6.83 % was achieved without selenization and ligand exchange. The value is comparable with the performance of control device using a Pt as counter electrode (power conversion efficiency: 7.08 %) under the same device architecture. IntroductionTernary and quaternary semiconductor nanocrystals (NCs) (e.g., CuInS 2 , CuInSe 2 , CuInGaS 2 , CuZnSnS 4 ) with advantages of tunable bandgaps and more environmentally friendly constituents have been receiving great attentions for solar-harvesting and light-emitting applications, in particular for solution-processed devices. 1-17 For example, CuInS 2 NCs are regarded as promising candidates as light absorber or counter electrode (CE) in dye-sensitized solar cells (DSSCs), due to the advantage of low cost and simple fabrication process. 18-23 Because the electronic structure of these materials strongly correlate with the [Cu]/[In] ratios, there is a great need to precisely control their size, shape, surface and compositions. 3,19,24,25 Although great success has been made in synthesis of ternary and quaternary NCs, providing several routes including thermal decomposition of single precursors, 26-30 solvothermal synthesis approach, 31-33 hot-injection 4,5,34-36 and non-injection methods, 7, 37-41 the different reactivity of metallic cation precursors often leads to a poor stoichiometric control and the formation of intermediate products such as biphasic nanomaterials and heterostructures. [42][43][44][45] To overcome such drawbacks of the composition control,

Folded Nanosheets: A New Mechanism for Nanodisk Formation

“…TEM indicated that large, wrinkled nanosheets had formed (Fig 4a, Fig S11). It has been shown previously that Cu + intercalation can occur at room temperature yielding CIS nanocrystals from In 2 S 3 nanocrystals, 26 However, the observed pattern was in good agreement with results from Rogach et al, who assigned their CIS product to the chalcopyrite phase. 26 When CuCl, InCl 3 and thiourea were heated together in a single step, small (~2 nm), spherical particles were observed (Fig S13, S14).…”

“…30 Rogach et al incorporated Cu + into In 2 S 3 nanoplates, resulting in CIS with tunable band gap that was used as an efficient counter electrode in dye-sensitized solar cells. 26 Bottom-up approaches, in which growth is limited in one or more dimensions, are typically used to prepare nanostructures such as nanowires and nanoparticles. [31][32][33] In contrast, 2D nanostructures can famously be formed via top-down approaches, such as the separation of 4 graphene and MoS 2 sheets through mechanical or chemical stress.…”

Synthesis of Ag/CuInS₂ Core-Shell Nanoparticles

“…Due to the af nity of thiol to Cu, CuInS 2 NPs with Cu-rich surfaces are considered energetically favored 12) . Chen et al 21) reported that Cu 3 InS 3 nanocrystals, which contain 3 times as many Cu atoms as In atoms, could take a chalcopyrite structure.…”

An Interconnected Ternary MIn2S4 (M=Fe, Co, Ni) Thiospinel Nanosheet Array: A Type of Efficient Platinum‐Free Counter Electrode for Dye‐Sensitized Solar Cells

“…[6] Among of them, the binary transitional-metal sulfides are an attractive family owing to their excellent catalytic activity for I 3 À reduction, the selectivity of transition metals,a nd versatile crystalline morphologies,s uch as WS 2 and MoS 2 . [15] Theextraordinary performance can be traced back to the fascinating morphologies,r ich redox reactions,t unable band-gap structures,a nd diverse photoelectric properties,w hich can be realized by adjusting the component elements and alternating the stoichiometric ratio. [9][10][11] Besides,t he ternary transition-metal sulfides have also been used as the promising CEs and achieved excellent device performances,s uch as NiCo 2 S 4 , [12] MMoS 4 (M = Co,N i), [13] Cu 3 SnS 4 , [14] CuInS 2 .…”

“…[7,8] Apart from the above-mentioned examples,b inary iron-group transition-metal sulfides,s uch as FeS 2 ,C oS,a nd NiS 2 ,a lso exhibit high catalytic activity for I 3 À reduction. [12][13][14][15][16] As one type of important ternary transition-metal sulfides,t he thiospinels (A II B III 2 X VI 4 ,s uch as CoIn 2 S 4 and NiIn 2 S 4 )have exhibited the viability of photocatalysis and the potential applications in optoelectronics,l ight modulators, and photodetectors. [15] Theextraordinary performance can be traced back to the fascinating morphologies,r ich redox reactions,t unable band-gap structures,a nd diverse photoelectric properties,w hich can be realized by adjusting the component elements and alternating the stoichiometric ratio.…”