# Iodide Salt Surface Etching Reduces Energy Loss in CdTe Nanocrystal Solar Cells

## TL;DR

A new iodide salt treatment improves CdTe nanocrystal solar cells by reducing energy loss and boosting efficiency.

## Contribution

A novel 2-iodothiophene wet etching method is introduced to enhance CdTe NC solar cell performance.

## Key findings

- Surface treatment with 2-iodothiophene reduces interface defects and improves carrier mobility.
- CdTe NC solar cells achieved 4.31% power conversion efficiency, higher than NH4I-treated cells at 3.08%.
- Iodide salt treatment increases voltage and reduces carrier recombination in the back contact.

## Abstract

CdTe nanocrystals (NCs) have emerged as a promising active layer for efficient thin-film solar cells due to their outstanding optical properties and simple processing techniques. However, the low hole concentration and high resistance in the CdTe NC active layer lead to high carrier recombination in the back contact. Herein, we developed a novel 2-iodothiophene as a wet etching solution to treat the surface of CdTe NC. We found that surface treatment using 2-iodothiophene leads to reduced interface defects and improves carrier mobility simultaneously. The surface properties of CdTe NC thin films after iodide salt treatment are revealed through surface element analysis, space charge limited current (SCLC) studies, and energy level investigations. The CdTe NC solar cells with 2-iodothiophene treatment achieved power conversion efficiency (PCE) of 4.31% coupled with a higher voltage than in controlled devices (with NH4I-treated ones, 3.08% PCE).