High Fidelity Polycrystalline CdTe/CdS Heterostructures via Molecular Dynamics

Abstract

Molecular dynamics simulations of polycrystalline growth of CdTe/CdS heterostructures have been performed. First, CdS was deposited on an amorphous CdS substrate, forming a polycrystalline film. Subsequently, CdTe was deposited on top of the polycrystalline CdS film. Cross-sectional images show grain formation at early stages of the CdS growth. During CdTe deposition, the CdS structure remains almost unchanged. Concurrently, CdTe grain boundary motion was detected after the first 24.4 nanoseconds of CdTe deposition. With the elapse of time, this grain boundary pins along the CdS/CdTe interface, leaving only a small region of epitaxial growth. CdTe grains are larger than CdS grains in agreement with experimental observations in the literature. Crystal phase analysis shows that zinc blende structure dominates over the wurtzite structure inside both CdS and CdTe grains. Composition analysis shows Te and S diffusion to the CdS and CdTe films, respectively. These simulated results may stimulate new ideas for studying and improving CdTe solar cell efficiency.

Molecular Dynamics Calculations of Grain Boundary Mobility in CdTe

“…A Stillinger-Weber (SW) potential [11,12] was used in our simulations. This potential is chosen because it both captures accurately the experimental atomic volumes, cohesive energies, and elastic properties of CdTe [12], and predicts the crystalline growth of II-VI compounds correctly [13]. Since the potential has been widely used to study grain structures in CdTe/CdS systems [3,13,14,15,16], knowledge of GB mobilities using the same potential has an additional advantage for comparing to previous studies.…”

A computational approach to analyze grain structures of semiconductor compound films: Case study of CdTe/CdS multilayers

“…For example, in CdTe/CdS based solar cells, the nature of the polycrystalline heterointerface has a strong influence on the energy conversion efficiency but identifying and tracking the evolution of important features during their formation is a challenging problem [1]. Molecular dynamics simulation of crystal growth yields time-resolved 3-dimensional structural data sets with atomic scale resolution that are amenable to detailed analysis [2]. Different types of postprocessing analyses such as stress and energy analysis of the computational samples are readily available.…”