Solution-Processed Cu₂ZnSnS₄ Nanocrystal Solar Cells: Efficient Stripping of Surface Insulating Layers Using Alkylating Agents

Abstract

Solution-processed photovoltaic (PV) devices based on semiconductor nanocrystals (NCs) such as Cu 2 ZnSnS 4 (CZTS) and CuInS 2 (CIS) are attracting much attention for use in next-generation solar cells. However, the performance of NCbased devices is hindered by insulating surface-capping ligands that limit transfer/transport of charged carriers. Here, to remove surface-capping ligands (long-chain fatty amines) from NCs, we use the strong alkylating agent methyl iodide, which converts primary amines to quaternary amines that have low coordinating affinity to the NC surface. X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy analyses confirm the successful removal of capping ligands from the CZTS surface after treatment with methyl iodide without changing the crystal structure of CZTS. CZTS and CIS NC-based devices treated with methyl iodide exhibit a reproducible PV response under simulated sunlight. The developed route can potentially enhance the performance of NC-based devices used in a broad range of applications.

Cadmium effect on optical properties of Cu2Zn1−xCdxSnS4 quinternary alloys nanostructures

“…3. The nanostructures were copper-poor and zinc-rich at all x contents except for x = 1 (Suehiro et al, 2014;Fischereder et al, 2010;Jiang et al, 2011). This indicates a higher p-type conductivity, which can be useful for PV applications (Chen et al, 2010).…”

Influence of Processing Conditions on the Performance of Cu2ZnSnS4 Nanocrystal Solar Cells

“…Previously, we demonstrated that ligand striping with alkylating agents such as methyl iodide and the Meerwein's reagent is effective in producing CZTS NC‐based solar cells without heat treatments at higher temperatures . The use of alkylating agents allowed for the removal of capping agents at moderate conditions such as lower temperatures, which is very important for some applications where NC layers should be used without high temperature annealing.…”

Visible‐Light Sensitization and Photoenergy Storage in Quantum Dot/Polyoxometalate Systems

“…They also developed all‐semiconductor NC solar cells with CdSe (n‐type) and CdTe (p‐type) NCs 2. So far, a variety of semiconductor NCs, such as CdTe,3, 4 PbS x Se 1− x ,5, 6 Cu 2 S,7 CuInSe 2 ,8, 9 and Cu 2 ZnSnS 4 ,10, 11 have been used for such NC‐based solar cells. These cells rely on the carrier transfer between n‐ and p‐type NCs.…”