Name: developing high performance gap/si heterojunction solar cells
Uploaded: 2018-11-16T15:00:00
Description: Watch this Scientific Journal Video about Developing High Performance GaP/Si Heterojunction Solar Cells at JoVE.com

The authors would like to thank L. Ding and M. Boccard for their contributions in processing and testing of the solar cells in this study. The authors acknowledge funding from the U.S. Department of Energy under contract DE-EE0006335 and the Engineering Research Center Program of the National Science Foundation and the Office of Energy Efficiency and Renewable Energy of the Department of Energy under NSF Cooperative Agreement No. EEC-1041895.&#160;Som Dahal at Solar Power Lab was supported, in part, by NSF contract ECCS-1542160.

CAUTION: Please consult all relevant material safety data sheets (MSDS) before dealing with chemicals. Please use all appropriate safety practices when performing a solar cell fabrication including the fume hood and personal protective equipment (safety glasses, gloves, lab coat, full-length pants, closed-toe shoes).
1. Si Wafer Cleaning
<ol>
	<li>Clean Si wafers in Piranha solution (H2O2/H2SO4) at 110 &#176;C.
	<ol>
		<li>To produce Piranha soluti...

<ol>
	<li>Friedman, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Progress+and+challenges+for+next-generation+high-efficiency+multijunction+solar+cells.">Progress and challenges for next-generation high-efficiency multijunction solar cells.</a> Current Opinion in Solid State &amp; Materials Science. 14, 131-138 (2010).</li><li>Vadiee, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AlGaSb-Based+Solar+Cells+Grown+on+GaAs:+Structural+investigation+and+device+performance.">AlGaSb-Based Solar Cells Grown on GaAs: Structural investigation and device performance.</a> IEEE Journal of Photovoltaics. , (2017).</li><li>Wagner, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+numerical+simulation+study+of+gallium-phosphide/silicon+heterojunction+passivated+emitter+and+rear+solar+cells.">A numerical simulation study of gallium-phosphide/silicon heterojunction passivated emitter and rear solar cells.</a> Journal of Applied Physics. 115, 044508 (2014).</li><li>Limpert, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Results+from+coupled+optical+and+electrical+sentaurus+TCAD+models+of+a+gallium+phosphide+on+silicon+electron+carrier+selective+contact+solar+cell.">Results from coupled optical and electrical sentaurus TCAD models of a gallium phosphide on silicon electron carrier selective contact solar cell.</a> 2014 IEEE 40th Photovoltaic Specialist Conference (PVSC). , 836-840 (2014).</li><li>Ding, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+source+of+silicon+minority-carrier+lifetime+degradation+during+molecular+beam+heteroepitaxial+growth+of+III-V+materials.">On the source of silicon minority-carrier lifetime degradation during molecular beam heteroepitaxial growth of III-V materials.</a> 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC). , 2048-2051 (2016).</li><li>Ding, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silicon+minority-carrier+lifetime+degradation+during+molecular+beam+heteroepitaxial+III-V+material+growth.">Silicon minority-carrier lifetime degradation during molecular beam heteroepitaxial III-V material growth.</a> Energy Procedia. 92, 617-623 (2016).</li><li>Zhang, C., Kim, Y., Faleev, N. N., Honsberg, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improvement+of+GaP+crystal+quality+and+silicon+bulk+lifetime+in+GaP/Si+heteroepitaxy.">Improvement of GaP crystal quality and silicon bulk lifetime in GaP/Si heteroepitaxy.</a> Journal of Crystal Growth. 475, 83-87 (2017).</li><li>Garc&#237;a-Tabar&#233;s, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+of+silicon+bulk+lifetime+during+III-V-on-Si+multijunction+solar+cell+epitaxial+growth.">Evolution of silicon bulk lifetime during III-V-on-Si multijunction solar cell epitaxial growth.</a> Progress in Photovoltaics: Research and Applications. 24, 634-644 (2016).</li><li>Varache, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+of+bulk+c-Si+properties+during+the+processing+of+GaP/c-Si+heterojunction+cell.">Evolution of bulk c-Si properties during the processing of GaP/c-Si heterojunction cell.</a> Energy Procedia. 77, 493-499 (2015).</li><li>Ishizaka, A., Shiraki, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low+temperature+surface+cleaning+of+silicon+and+its+application+to+silicon+MBE.">Low temperature surface cleaning of silicon and its application to silicon MBE.</a> Journal of The Electrochemical Society. 133, 666 (1986).</li><li>Zhang, C., Vadiee, E., King, R. R., Honsberg, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carrier-selective+contact+GaP/Si+solar+cells+grown+by+molecular+beam+epitaxy.">Carrier-selective contact GaP/Si solar cells grown by molecular beam epitaxy.</a> Journal of Materials Research. 33, 414-423 (2018).</li><li>Battaglia, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hole+Selective+MoOx+Contact+for+Silicon+Solar+Cells.">Hole Selective MoOx Contact for Silicon Solar Cells.</a> Nano Letters. 14, 967-971 (2014).</li></ol>

A nominal 25 nm-thick GaP layer was epitaxially grown on a P-rich Si surface via MBE. To grow a better quality of GaP layer on Si substrates, a relatively low V/III (P/Ga) ratio is preferable. A good crystal quality of GaP layer is necessary to achieve high conductivity and low density of recombination centers. The AFM root-mean-square (RMS) of the GaP surface is ~0.52 nm showing a smooth surface with no pits, indicative of high crystal quality with a low threading dislocation density (Figure 1a</str...

There has been a continuing effort on the integration of different materials with lattice mismatches in order to enhance overall solar cell efficiency1,2. The III-V/Si integration has the potential to further increase the current Si solar cell efficiency and replace the expensive III-V substrates (such as GaAs and Ge) with a Si substrate for multijunction solar cell applications. Among all III-V binary material systems, gallium phosphide (GaP) is a good candidate for this purpose, as it has the smallest lattice-mismatch (~0.4%) with Si and a high indirect bandgap. These features can enable high-quality integration of GaP with Si substrate. It has been theoretically shown that GaP/Si heterojunction solar cells could enhance the efficiency of conventional passivated emitter rear Si solar cells3,4 by benefiting from the unique band-offset between GaP and Si (&#8710;Ev ~1.05 eV and &#8710;Ec ~0.09 eV). This makes GaP a promising electron selective contact for silicon solar cells. However, in order to achieve high-performance GaP/Si heterojunction solar cells, a high Si bulk lifetime and high GaP/Si interface quality are required.
During the growth of III-V materials on a Si substrate by molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE), significant Si lifetime degradation has been widely observed5,6,7,8,9. It was revealed that the lifetime degradation mainly happens during the thermal treatment of the Si wafers in the reactors, which is required for surface oxide desorption and/or surface reconstruction before the epitaxial growth10. This degradation was ascribed to the extrinsic diffusion of contaminants originated from the growth reactors5,7. Several approaches have been proposed to suppress this Si lifetime degradation. In our previous work, we have demonstrated two methods in which the Si lifetime degradation can be significantly suppressed. The first method was demonstrated by the introduction of SiNx as a diffusion barrier7 and the second one by introducing the P-diffusion layer as a gettering agent11 to the Si substrate.
In this work, we have demonstrated high-performance GaP/Si solar cells based on the aforementioned approaches to mitigate the silicon bulk lifetime degradation. The techniques used to preserve the Si lifetime can have broad applications in multijunction solar cells with active Si bottom cells and electronic devices such as high-mobility CMOS. In this detailed protocol, the fabrication details of GaP/Si heterojunction solar cells, including Si wafer cleaning, P-diffusion in the furnace, GaP growth, and GaP/Si solar cells processing, are presented.

<table>
	<tbody>
		<tr>
			<td>Hydrogen peroxide, 30%</td>
			<td>Honeywell</td>
			<td>10181019</td>
			<td></td>
		</tr>
		<tr>
			<td>Sulfuric acid, 96%</td>
			<td>KMG electronic chemicals, Inc.</td>
			<td>64103</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric acid, 37%</td>
			<td>KMG electronic chemicals, Inc.</td>
			<td>64009</td>
			<td></td>
		</tr>
		<tr>
			<td>Buffered Oxide Etch 10:1</td>
			<td>KMG electronic chemicals, Inc.</td>
			<td>62060</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrofluoric acid, 49%</td>
			<td>Honeywell</td>
			<td>10181736</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic acid</td>
			<td>Honeywell</td>
			<td>10180830</td>
			<td></td>
		</tr>
		<tr>
			<td>Nitride acid, 69.5%</td>
			<td>KMG electronic chemicals, Inc.</td>
			<td>200288</td>
			<td></td>
		</tr>
	</tbody>
</table>

developing high performance gap/si heterojunction solar cells

To improve the efficiency of Si-based solar cells beyond their Shockley-Queisser limit, the optimal path is to integrate them with III-V-based solar cells. In this work, we present high performance GaP/Si heterojunction solar cells with a high Si minority-carrier lifetime and high crystal quality of epitaxial GaP layers. It is shown that by applying phosphorus (P)-diffusion layers into the Si substrate and a SiNx layer, the Si minority-carrier lifetime can be well-maintained during the GaP growth in the molecular beam epitaxy (MBE). By controlling the growth conditions, the high crystal quality of GaP was grown on the P-rich Si surface. The film quality is characterized by atomic force microscopy and high-resolution x-ray diffraction. In addition, MoOx was implemented as a hole-selective contact that led to a significant increase in the short-circuit current density. The achieved high device performance of the GaP/Si heterojunction solar cells establishes a path for further enhancement of the performance of Si-based photovoltaic devices.

Atomic force microscopy (AFM) images and high-resolution x-ray diffraction (XRD) scans, including the rocking curve in the vicinity of the (004) reflection and the reciprocal space map (RSM) in the vicinity of (224) reflection, were collected for the GaP/Si structure (Figure 1). The AFM was used to characterize the surface morphology of the MBE-grown GaP and XRD was used to examine the crystal quality of GaP layer. The effective minority-carrier lifetime of t...

Watch this Scientific Journal Video about Developing High Performance GaP/Si Heterojunction Solar Cells at JoVE.com

Developing High Performance GaP/Si Heterojunction Solar Cells

Here, we present a protocol to develop high-performance GaP/Si heterojunction solar cells with a high Si minority-carrier lifetime.

To improve the efficiency of Si-based solar cells beyond their Shockley-Queisser limit, the optimal path is to integrate them with III-V-based solar ...

Research

JoVE Journal

Engineering

Research and Development of High-performance Explosives

Developmental testing of high explosives for military applications involves small-scale formulation, safety testing, and finally detonation performance ...

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices ...

Digital Printing of Titanium Dioxide for Dye Sensitized Solar Cells

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less ...

Probing C84-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics

Probing C84-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics

This paper reports an array-designed C84-embedded Si substrate fabricated using a controlled self-assembly method in an ultra-high vacuum chamber. The ...

A High Performance Impedance-based Platform for Evaporation Rate Detection

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was ...

Morphology Control for Fully Printable Organic&#8211;Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

Morphology Control for Fully Printable OrganicÃƒÆ’Ã‚Â¢ÃƒÂ¢Ã¢â‚¬Å¡Ã‚Â¬ÃƒÂ¢Ã¢â€šÂ¬Ã…â€œInorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

The photoactive layer of a typical organic thin-film bulk-heterojunction (BHJ) solar cell commonly uses fullerene derivatives as the electron-accepting ...

Monovalent Cation Doping of CH3NH3PbI3 for Efficient Perovskite Solar Cells

Monovalent Cation Doping of CH3NH3PbI3 for Efficient Perovskite Solar Cells

Here, we demonstrate the incorporation of monovalent cation additives into CH3NH3PbI3 perovskite in order to adjust the optical, excitonic, and electrical ...

Electrospinning of Photocatalytic Electrodes for Dye-sensitized Solar Cells

This work demonstrates a protocol to fabricate a fiber-based photoanode for dye-sensitized solar cells, consisting of a light-scattering layer made of ...

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for Cu(In,Ga)Se2 Solar Cells

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for CuIn,GaSe2 Solar Cells

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction ...

Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a ...