Shahzada Qamar Hussain

Ultrathin Oxide Passivation Layer by Rapid Thermal Oxidation for the Silicon Heterojunction Solar Cell Applications

It is difficult to deposit extremely thin a-Si:H layer in heterojunction with intrinsic thin layer (HIT) solar cell due to thermal damage and tough process control. This study aims to understand oxide passivation mechanism of silicon surface using rapid thermal oxidation (RTO) process by examining surface effective lifetime and surface recombination velocity. The presence of thin insulating a-Si:H layer is the key to get high by lowering the leakage current (I0) which improves the efficiency of HIT solar cell. The ultrathin thermal passivation silicon oxide (SiO2) layer was deposited by RTO system in the temperature range 500–950°C for 2 to 6 minutes. The thickness of the silicon oxide layer was affected by RTO annealing temperature and treatment time. The best value of surface recombination velocity was recorded for the sample treated at a temperature of 850°C for 6 minutes at O2 flow rate of 3 Lpm. A surface recombination velocity below 25 cm/s was obtained for the silicon oxide layer of 4 nm thickness. This ultrathin SiO2 layer was employed for the fabrication of HIT solar cell structure instead of a-Si:H, (i) layer and the passivation and tunneling effects of the silicon oxide layer were exploited. The photocurrent was decreased with the increase of illumination intensity and SiO2 thickness.

Improvement of Mobility in Oxide-Based Thin Film Transistors: A Brief Review

Copyright ©2015 KIEEME. All rights reserved. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited. pISSN: 1229-7607 eISSN: 2092-7592 DOI: http://dx.doi.org/10.4313/TEEM.2015.16.5.234 OAK Central: http://central.oak.go.kr

Surface Passivation Schemes for High-Efficiency c-Si Solar Cells - A Review

Copyright ©2015 KIEEME. All rights reserved. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited. pISSN: 1229-7607 eISSN: 2092-7592 DOI: http://dx.doi.org/10.4313/TEEM.2015.16.5.227 OAK Central: http://central.oak.go.kr TRANSACTIONS ON ELECTRICAL AND ELECTRONIC MATERIALS Vol. 16, No. 5, pp. 227-233, October 25, 2015

Boosting the mobility and bias stability of oxide-based thin-film transistors with ultra- thin nanocrystalline InSnO:Zr layer

Extensive attention on high-definition flat panel displays is the driving force to fabricate high-performance thin-film transistors (TFTs). A hybrid oxide TFTs fabricated using an interfacial layer of nanocrystalline Zr-doped InSnO (nc-ITO:Zr) and an amorphous InSnZnO films as an active channel is reported here. Due to the presence of nc-ITO:Zr layer, an improvement of the field-effect mobility (86.4 cm2/V·s) and threshold voltage (0.43 V) values for TFTs are observed. Positive gate bias stress study indicates the role of nc-ITO:Zr layer in fabricated TFTs through the suppression of charge trapping capability between the channel and insulating layer.

RF magnetron sputtered ITO:Zr thin films for the high efficiency a-Si:H/c-Si heterojunction solar cells

ITO and ITO:Zr films with various thicknesses were prepared on glass substrates by RF magnetron sputtering. We observed a decrease in sheet resistance with increasing film thickness that in good agreement with Fuchs-Sondheimer theory. The ITO films doped with ZrO2 (∼0.2 wt%) showed improvement in some of the electrical and optical properties of ITO films. The surface roughness of ITO:Zr films increased with increasing film thickness. ITO:Zr films with thickness of 120 nm showed highest work function of 5.13 eV, as estimated from XPS data. The ITO:Zr films were employed as front electrodes in HIT solar cells; the best device performance was found to be: Voc = 710 mV, Jsc = 34.44 mA/cm2, FF = 74.8%, η = 18.30% at a thickness of 120 nm. A maximum quantum efficiency (QE) of 89% was recorded for HIT solar cells at a wavelength of 700 nm for 120 nm thick ITO:Zr films.

Plasma Textured Glass Surface Morphologies for Amorphous Silicon Thin Film Solar Cells-A review

Copyright ©2016 KIEEME. All rights reserved. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited. pISSN: 1229-7607 eISSN: 2092-7592 DOI: http://dx.doi.org/10.4313/TEEM.2016.17.2.98 OAK Central: http://central.oak.go.kr

Effect of Oxygen and Diborane Gas Ratio on P-type Amorphous Silicon Oxide films and Its Application to Amorphous Silicon Solar Cells

We reported diborane () doped wide bandgap hydrogenated amorphous silicon oxide (p-type a-SiOx:H) films prepared by using silane () hydrogen () and nitrous oxide () in a radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) system. We improved the and conductivity of p-type a-SiOx:H films with various and ratios and applied those films in regards to the a-Si thin film solar cells. For the single layer p-type a-SiOx:H films, we achieved an optical band gap energy () of 1.91 and 1.99 eV, electrical conductivity of approximately S/cm and activation energy () of 0.57 to 0.52 eV with various and ratios. We applied those films for the a-Si thin film solar cell and the current-voltage characteristics are as given as:

HF etched glass substrates for improved thin-film solar cells

A hemisphere-array textured glass substrate was fabricated for the development of an improved thin-film (TF) silicon solar cell. The HF-H2SO4-etchant system influenced the light path owing to the formation of the strong fluorine-containing HSO3F acid. In particular, the etching system of the various HF concentration with a constant H2SO4 solution is related to make an improvement of optical transmittance and light trapping structure without a uniform pattern. According to the specular transmittance measurements, the haze ratio was maintained for the glass sample etched with 35% HF in the longer-wavelength region. The proposed substrate was implemented in a TF-Si solar cell, and an improved conversion efficiency was observed according to the short-circuit current density owing to the increase in the haze ratio. This morphology, therefore, induces more scattering at the front side of the cell and leads to an improvement of the open circuit voltage gain for the HF 25% cell. It will be helpful to understand the application of thin film solar cell based on the HF-H2SO4 etching system for the readers.

Light scattering through multi-textured periodic glass surface morphologies for a-Si thin film solar cells

Front transparent conductive oxide (TCO) films play a vital role in amorphous silicon based thin film solar cells due to their high transparency, conductivity and excellent light scattering properties. The precise surface morphology with better step coverage for the front TCO films is a hot research topic now a days. Since the low step coverage of TCO films suffered non uniformity and hence low performance of amorphous silicon thin film solar cells (a-Si TFSCs). We report novel multi-textured periodic textured glass surface morphologies with high transmittance and better step coverage of AZO films for the a-Si TFSCs. The SF6/Ar plasma etching of glass substrates was used for the high roughness and haze ratio while wet (Buffered Hydro Fluoric acid (BHF)) chemical etching was performed for the better step coverage by controlling the shape of textured glass surface morphology. The pyramid shaped textured glass surface morphologies offered the lowest sheet resistance, high transmittance and roughness for the RF magnetron sputtered AZO films. The AZO films showed the highest total transmittance and haze ratio of 90.19% and 54.29% in the visible wavelength region with lowest sheet resistance of 6.242 Ω/□ for 800 nm thickness. The AZO films deposited on the pyramid glass surface showed the better step coverage. The minor variation in sheet resistance and resistivity of the AZO films was related to the step coverage of the AZO films that is closely related with the shape and angle of the surface morphology. The AZO films with low sheet resistance, high transmittance and step coverage can be employed to improve the performance of future a-Si thin film solar cells.