# Phase-Controlled Synthesis of Alloyed (CdS)x(CuInS2)1−x Nanocrystals with Tunable Band Gap

## TL;DR

Scientists developed a method to create nanocrystals with adjustable properties for use in solar cells and catalysts.

## Contribution

A precursor-mediated colloidal method enables phase-controlled synthesis of alloyed nanocrystals with tunable band gaps.

## Key findings

- Wurtzite-structured nanocrystals have tunable band gaps from 1.56 to 2.45 eV by adjusting Cd precursor molar ratio.
- Zinc-blende structured nanocrystals show band gaps from 1.50 to 1.84 eV with precise Cd precursor control.
- Characterization methods like XRD, TEM, and XPS confirmed the structural and optical properties of the nanocrystals.

## Abstract

Phase and band gap engineering of (CdS)x(CuInS2)1−x nanomaterials is critical for their potential applications in photovoltaics and photocatalysis, yet it remains a challenge. Here, we report a precursor-mediated colloidal method for phase-control synthesis of alloyed (CdS)x(CuInS2)1−x nanocrystals with tunable band gap. When CuCl, InCl3, and Cd(AC)2·2H2O are used as the respective cation sources, wurtzite-structured alloyed (CdS)x(CuInS2)1−x nanocrystals can be synthesized with a tunable optical band gap ranging from 1.56 to 2.45 eV by directly controlling the molar ratio of the Cd precursor. Moreover, using Cu(S2CNEt2)2, In(S2CNEt2)3, and Cd(S2CNEt2)2 as cation sources results in alloyed (CdS)x(CuInS2)1−x nanocrystals with a zinc-blende structure, demonstrating that the optical band gap of these nanocrystals can be compositionally tuned from 1.50 to 1.84 eV through precisely adjusting the molar ratio of Cd precursor. The results were validated through a comprehensive characterization approach employing XRD, TEM, HRTEM, STEM-EDS, XPS, UV-vis-NIR absorption spectroscopy, and Mott–Schottky analysis.