Growth and characterization of textured well-faceted ZnO on planar Si(100), planar Si(111), and textured Si(100) substrates for solar cell applications.

Jyong-Di Lai,Fann-Wei Yang,Shih-Wei Feng,Li-Wei Tu,Chin-Yi Tsai,Chien-Jung Huang,Hsiang-Chen Wang,Chien-Hsun Chen

doi:10.3762/bjnano.8.194

Abstract

In this work, textured, well-faceted ZnO materials grown on planar Si(100), planar Si(111), and textured Si(100) substrates by low-pressure chemical vapor deposition (LPCVD) were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and cathode luminescence (CL) measurements. The results show that ZnO grown on planar Si(100), planar Si(111), and textured Si(100) substrates favor the growth of ZnO(110) ridge-like, ZnO(002) pyramid-like, and ZnO(101) pyramidal-tip structures, respectively. This could be attributed to the constraints of the lattice mismatch between the ZnO and Si unit cells. The average grain size of ZnO on the planar Si(100) substrate is slightly larger than that on the planar Si(111) substrate, while both of them are much larger than that on the textured Si(100) substrate. The average grain sizes (about 10–50 nm) of the ZnO grown on the different silicon substrates decreases with the increase of their strains. These results are shown to strongly correlate with the results from the SEM, AFM, and CL as well. The reflectance spectra of these three samples show that the antireflection function provided by theses samples mostly results from the nanometer-scaled texture of the ZnO films, while the micrometer-scaled texture of the Si substrate has a limited contribution. The results of this work provide important information for optimized growth of textured and well-faceted ZnO grown on wafer-based silicon solar cells and can be utilized for efficiency enhancement and optimization of device materials and structures, such as heterojunction with intrinsic thin layer (HIT) solar cells.

Highlights

Transparent conductive oxides (TCOs), with both high electrical conductivity and optical transparency, could be used as a replacement for the metal contact in semiconductor devices
It was reported that three types of textured ZnO thin film, the columnar/ polygonal, pyramid-like, and crater-like/pyramidal-tip textured structures, were grown as a front electrode in wafer-based silicon solar cells and had different influence on the performance of solar cells [11]
In this work, textured and well-faceted ZnO samples are grown on planar Si(100), planar Si(111), and textured Si(100) substrates by the lowpressure chemical vapor deposition (LPCVD) method

Summary

Introduction

Transparent conductive oxides (TCOs), with both high electrical conductivity and optical transparency, could be used as a replacement for the metal contact in semiconductor devices. ZnO grown on bulk silicon substrates and their application to wafer-based silicon solar cells is an interesting issue and an important subject [3] In such a case, these materials potentially act as metal contacts to eliminate the blocking of the incident sunlight from the metals, but they can serve the function of antireflection coating (ARC) films, given proper design of the film thickness. In the most optimal case, a single ZnO film can simultaneously act as a contact, ARC, and emitter for a wafer-based silicon solar cell Such a device would dramatically reduce the manufacture process and associated cost of solar cell production. This example illustrates the importance and great potential regarding the subject of granular ZnO thin films grown on crystalline silicon substrates

Results

Discussion

Conclusion