Study of n-Type Fe2O3 and p-Type CuO Thin Films for Two Energy Gap Tandem Solar Cell Application
Date Issued
2005
Date
2005
Author(s)
Yang, Ming-Hang
DOI
zh-TW
Abstract
In this study, we have designed a silicon based multi-junction solar cell to answer to energy requirements and economical benefits. To fit in the design parameters (multi-band gap、cost、stability), n type α-Fe2O3 and p type CuO were chosen as the suitable high energy gap materials. Therefore, the preparation of n-Fe2O3/p-CuO|n-Si/p-Si device was the expected ultimate goal; and the preparation of Fe2O3 and CuO thin films with high photoelectrical efficiency was the initial major target of this research.
From the preparation of Fe2O3 thin films by applying the method of RF magnetron sputter-deposition, it was found that p type samples were made in oxygen plasma gas. After post annealing in 600℃, the samples became n type. When these n-type Fe2O3 films were doped with different amounts of Ti, the one with 0.2at％ Ti had the highest photo/dark conductivity ratio (i.e., 3.21) and the highest dark conductivity (i.e., 6.38×10-7 ohm-1．cm-1). Moreover, when the films were doped with 1at% Ti and prepared in different plasma gases (Ar, O2, or mixture of Ar and O2), the one from the plasma gas composition Ar/O2 (90/10) had the highest photo/dark conductivity ratio (i.e., 3.12).
CuO thin films were spin-coated on the substrates from the sol-gel prepared in this research. The thicker films can be from the multi-layers coating. However, it was found that CuO films were easier to convert photon energy to heat after illumination, which led low photo/dark ratio (i.e., about 1.1). Changing the composition of sol-gel solution would result in different grain sizes and crystal densities. When CuO films doped with Li, the grain size went down with increasing Li doping concentration. The dark conductivity was raised from 5.04×10-4 (of pure CuO) to 1.33×10-3 ohm-1cm-1 (of CuO doped with 2.05 at%Li). Nevertheless, the photo/dark ratios of all the CuO films prepared from this study were just around 1.1.
The energy gaps of α-Fe2O3 and CuO films prepared in this research were around 1.85eV and 1.68eV respectively, which met the high energy gap requirement expected from the design of silicon based multi-junction solar cell. However, all the photo/dark ratios were too low, which were not sufficient in application. Therefore, more efforts need to be put in the future, in order to achieve the ultimate goal of n-Fe2O3/p-CuO|n-Si/p-Si device.
Subjects
多重能隙
氧化鐵
氧化銅
光/暗電導率
太陽能電池
multi-bandgap
Fe2O3
CuO
photo/dark conductivity ratio
solar cell
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-94-R92524075-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):fd9a7800fea6df5f39a204071299d120