Enhanced photovoltaic property by forming p-i-n structures containing Si quantum dots/SiC multilayers.

Yunqing Cao,Kunji Chen,Xiaowei Zhang,Ling Xu,Jun Xu,Peng Lu

doi:10.1186/1556-276x-9-634

Abstract

Si quantum dots (Si QDs)/SiC multilayers were fabricated by annealing hydrogenated amorphous Si/SiC multilayers prepared in a plasma-enhanced chemical vapor deposition system. The thickness of amorphous Si layer was designed to be 4 nm, and the thickness of amorphous SiC layer was kept at 2 nm. Transmission electron microscopy observation revealed the formation of Si QDs after 900°C annealing. The optical properties of the Si QDs/SiC multilayers were studied, and the optical band gap deduced from the optical absorption coefficient result is 1.48 eV. Moreover, the p-i-n structure with n-a-Si/i-(Si QDs/SiC multilayers)/p-Si was fabricated, and the carrier transportation mechanism was investigated. The p-i-n structure was used in a solar cell device. The cell had the open circuit voltage of 532 mV and the power conversion efficiency (PCE) of 6.28%.PACS81.07.Ta; 78.67.Pt; 88.40.jj

Highlights

Si-based solar cells have been widely used due to its abundance, contaminant-free, and mature fabrication process
It is noted that only one broad band centered at 480 cm−1 exists in the as-deposited sample, which is attributed to the transverse optical (TO) mode of amorphous Si-Si bonds
An intense peak at 517 cm−1 associated with crystallized Si TO mode appears for 900°C annealed sample, which indicates that the amorphous Si layers have been crystallized to form nano-crystallized Si

Summary

Introduction

Si-based solar cells have been widely used due to its abundance, contaminant-free, and mature fabrication process. For a single p-n junction crystalline silicon solar cell, the maximum theoretical power conversion efficiency is only 29.8%, because of the inevitable longer and shorter wavelength loss [1]. It was reported that the broadband spectral absorption can be realized by forming the all Sibased tandem type solar cells, whose power conversion efficiency can exceed the Shockley-Queisser limit [4,5,6]. It is interesting to study the photovoltaic properties of Si QDs-based structures for their actual applications in devices. Park et al studied Si QDs/c-Si heterojunction solar cells based on

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Results

Conclusion