This work was partially supported by JSPS KAKENHI Grant Number 25871029, the Nippon Sheet Glass Foundation for Materials Science and Engineering, and the Tochigi Industrial Promotion Center. The National Institute of Technology, Oyama College, also assisted with the publication costs of this article.

1. Preparation of Indium-tin-oxide (ITO) Glass for Solar Cell Fabrication
<ol>
	<li>Cut the ITO/glass substrate.
	<ol>
		<li>Using a glass cutter, cut the ITO/glass substrate (10 cm &#215; 10 cm) into pieces measuring approximately 2 cm &#215; 2 cm.</li>
	</ol>
	</li>
	<li>Chemically etch the ITO conductive layer.
	<ol>
		<li>Using a digital multimeter, check that the top of the ITO/glass piece has a conductive side.</li>
		<li>Place masking tape on both sides of the ITO/glass piece, leaving a central area of 2 mm &#215; 2 cm in the middle. Using masking tape, protect the rest of the ITO conductive layer from the etching.</li>
		<li>Pour a few drops of HCl (1 M) onto the ITO conductive layer to remove the ITO conductive layer from the surface of the ITO/glass piece. After approximately 3 min, wipe off the HCl using a cotton swab, and then remove the masking tape.</li>
	</ol>
	</li>
	<li>Pretreat the ITO/glass piece.
	<ol>
		<li>Place the ITO/glass pieces in a glass case and fill the case with water.</li>
		<li>Place the glass case in a water bath that is two-thirds full of water and attach an ultrasonic cleaner. Then, turn on the ultrasonic cleaner for approximately 15 min to remove the few traces of chemical etchant remaining on the ITO/glass piece. Wash these pieces in an ultrasonic bath with water, acetone, and isopropyl alcohol, respectively, for 15 min each, and then dry them in a stream of dry air. Perform ultrasonication at an oscillatory frequency of 42 kHz.</li>
		<li>Place the ITO/glass pieces inside an ultraviolet-ozone (UV-O3) cleaner and run the machine for 30 min.</li>
	</ol>
	</li>
</ol>
2. Preparation of the Precursor Solution for the Photoactive Layer
<ol>
	<li>Dissolve 0.5 mg of poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT) as an electron donor and 1.0 mg of Ti-alkoxide in 1 mL of chlorobenzene. Select the following Ti-alkoxides as electron acceptors: Ti(IV) isopropoxide, ethoxide, butoxide, and butoxide polymer. Then, dissolve 0.5 mg of PFO-DBT and 1.0 mg of [60]PCBM in 1 mL of chlorobenzene as a reference. 
	NOTE: Here, the HOMO-LUMO levels are as follows21. PFO-DBT: 5.4-3.53 eV, Ti(IV) isopropoxide: 7.49-3.86 eV, ethoxide: 7.55-3.90 eV, butoxide: 7.53-3.76 eV, and butoxide polymer: 7.57-3.83 eV.</li>
	<li>On a magnetic hot stirrer, heat the precursor solution to 70 &#176;C while stirring it with a stir bar at a rotational speed of 700 rpm. Do this for 20 min in the absence of light, until the solution is visually clear to the naked eye. Cool the solution to room temperature, again in the absence of light, for future use.</li>
</ol>
3. Fabrication of the Photoactive Layer
<ol>
	<li>Deposit the film by spin-coating.
	<ol>
		<li>Heat the precursor solution of the photoactive layer and the ITO/glass piece to 70 &#176;C. For 10 min, heat the precursor solution on a magnetic hot stirrer heated to 70 &#176;C and use a stir bar at a rotational speed of 700 rpm. Heat the ITO/glass piece on a ceramic hot plate heated to 70 &#176;C for 5 min.</li>
		<li>Place the ITO/glass piece at the center of the vacuum stage of the spin coater, heat it with a heat gun to around 70 &#176;C, and turn on the vacuum. 
		NOTE: The vacuum is created by using a vacuum pump with a pumping speed of 30 L/min. The ultimate pressure of the vacuum pump is 26.6 &#215; 103 Pa.</li>
		<li>Pour a few drops of the precursor solution of the photoactive layer onto the ITO/glass piece and start the spin coater at 2,000-6,000 rpm for 60 s in air. 
		NOTE: The volume of precursor solution is 0.5 mL, measured with a 1-mL spuit.</li>
		<li>Dry the surface of the photoactive layer for 10 min at room temperature in an air atmosphere in the absence of light to obtain a 50 nm-thick film as the photoactive layer.</li>
	</ol>
	</li>
	<li>Remove the extra film.
	<ol>
		<li>Wipe the extra photoactive layer from the surface of the ITO/glass piece with a cotton swab wetted with chlorobenzene.</li>
		<li>Dry the photoactive layer again for 10 min at room temperature in an air atmosphere in the absence of light. 
		NOTE: The temperature of our experiment room is maintained at 25 &#176;C.</li>
	</ol>
	</li>
</ol>
4. Fabrication of the Electrode
<ol>
	<li>Print the organic electrode.
	<ol>
		<li>Using a screen printer, print an organic electrode by placing poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) on the photoactive layer22. The metal mask is 50 &#181;m-thick, and the printing area is 5 mm &#215; 20 mm.</li>
		<li>Dry the organic electrode for 30 min at room temperature in an air atmosphere in the absence of light.</li>
	</ol>
	</li>
</ol>
5. Lamination for the Solar Cells
<ol>
	<li>Cut the glass substrate into pieces with dimensions of 1.5 cm &#215; 2.5 cm using a diamond cutter. Spread an epoxy resin onto the glass substrate using a plastic spatula. Place the glass substrate with epoxy resin on the photoactive layer to protect it.</li>
</ol>
6. Preparation for Measuring the Solar-cell Performance
<ol>
	<li>Clean the electrodes by wiping them with a cotton swab wetted with acetone. Attach a supporting electrode onto the ITO using an ultrasonic soldering system. Operate the soldering iron at a 42-kHz frequency and at 230 &#176;C.</li>
</ol>
7. Measurement of the Solar-cell Performance
<ol>
	<li>Measure the current&#8211;voltage (J-V) characteristics of the solar cells by using a direct-current voltage current source/monitor integrated system, with the solar simulator calibrated to provide a simulated AM1.5G of 100 mW/cm2 by the silicon photodiode. 
	NOTE: More detailed information about the measurement of the J-V curves can be found elsewhere23, 24.</li>
</ol>
8. Analysis of the Phase-separation structure
<ol>
	<li>Prepare individual films of photoactive layers constructed with Ti-alkoxide and PFO-DBT, using same method for solar-cell fabrication, without the organic electrode and without the lamination process.</li>
	<li>Use an optical microscope or a scanning electron microscope (SEM) to observe the morphology of the photoactive layer at a high magnification (50,000&#215;) in order to analyze the phase-separation structure. 
	NOTE: More detailed information about SEM operation can be found elsewhere25, 26.</li>
</ol>

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The authors declare that they have no competing financial interests.

In order to utilize the molecule&#39;s bulkiness in this method, it is important to know the conditions for film formation by spin coating. First, the p-type and n-type semiconductors must be able to be dissolved in the solvents. When some material remains, it will become the large core of the domains in the photoactive layer. The use of an adequate commercial filter for individual solvents is recommended to remove the remaining material. Next, the precursor solution in which the molecules dissolve must be uniformly and ...

Organic photovoltaic devices are considered promising renewable energy sources due to their low manufacturing cost and light weight1-7. Because of these advantages, a large number of scientists have been immersed in this promising area. In the past decade, dye-sensitized, organic thin-film, and perovskite-sensitized solar cells have achieved significant progress in power conversion efficiency in this area8.
Specifically, organic thin-film solar cells and BHJ organic thin-film solar-cell technology are efficient and cost-effective solutions for the utilization of solar energy. Furthermore, the energy conversion efficiency has reached over 10% with the use of low-band-gap polymers as the electron donor and fullerene derivatives as the electron acceptor (Phenyl-C61-Butyric-Acid-Methyl Ester: [60]PCBM or Phenyl-C71-Butyric-Acid-Methyl Ester: [70]PCBM)9-11. Moreover, some researchers have already reported the importance of the BHJ structure in the photoactive layer, which is constructed with low-band-gap polymers and fullerene derivatives to obtain a high overall efficiency. However, fullerene derivatives are air-sensitive. Therefore, an air-stable electron-accepting material is required as an alternative. A few reports previously suggested new types of organic photovoltaic cells that used n-type semiconducting polymers or metal oxides as electron acceptors. These reports supported the development of air-stable, fullerene-free, organic thin-film solar cells12-15.
However, in contrast to fullerene systems or n-type semiconducting polymer systems, obtaining a satisfactory performance of the BHJ structure in the photoactive layer, which has charge separation and charge transfer abilities, is difficult in metal oxide systems16-17. Furthermore, fullerene derivatives and n-type semiconducting polymers have high solubility in many solvents. Therefore, it is easy to control the morphology of the photoactive layer by selecting an ink solution as the solvent, which is the precursor of the photoactive layer18-20. In contrast, in the case of metal alkoxide systems used in combination with an electron-donating polymer, both semiconductors are insoluble in almost all solvents. This is because metal alkoxides do not have a high solubility in the solvent. Therefore, the selectivity of solvents for morphology control is extremely low.
In this article, we report a method for controlling the morphology of the photoactive layer by using molecular bulkiness to fabricate printable and highly air-stable BHJ solar cells. We describe the importance of morphology control for the progress of fullerene-free BHJ solar cells.

<table><tbody><tr><td>Ti(IV) isopropoxide, 97%</td><td>Sigma Aldrich</td><td>205273</td><td></td></tr><tr><td>Ti(IV) ethoxide</td><td>Sigma Aldrich</td><td>244759</td><td>Technical grade</td></tr><tr><td>Ti(IV) butoxide, 97%</td><td>Sigma Aldrich</td><td>244112</td><td>Reagent grade</td></tr><tr><td>Ti(IV) butoxide polymer</td><td>Sigma Aldrich</td><td>510718</td><td></td></tr><tr><td>Poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT)</td><td>Sigma Aldrich</td><td>754013</td><td></td></tr><tr><td>[6,6]-phenyl-C&lt;sub&gt;61&lt;/sub&gt;-butyric acid methyl ester ([60]PCBM) 99.5%</td><td>Sigma Aldrich</td><td>684449</td><td>Research grade</td></tr><tr><td>poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS)</td><td>Heraeus</td><td>Clevios S V3</td><td></td></tr><tr><td>1 N Hydrochloric acid</td><td>Wako</td><td>083-01095</td><td></td></tr><tr><td>Chlorobenzene 99.0%</td><td>Wako</td><td>032-07986</td><td></td></tr><tr><td>Acetone 99.5%</td><td>Wako</td><td>016-00346</td><td></td></tr><tr><td>Indium-tin oxide (ITO)-coated glass substrate</td><td>Geomatec</td><td>0002</td><td>100&amp;times;100&amp;times;1.1t (mm)</td></tr><tr><td>Glass substrate</td><td>Matsunami Glass</td><td>S7213</td><td>76&amp;times;26&amp;times;1.2t (mm)</td></tr><tr><td>Cotton tail&amp;nbsp;</td><td>As one</td><td>1-8584-16</td><td></td></tr><tr><td>Epoxy resin</td><td>Nichiban</td><td>AR-R30</td><td></td></tr><tr><td>Plastic spatula</td><td>As one</td><td>2-3956-02</td><td></td></tr><tr><td>Ultrasonic cleaner</td><td>As one</td><td>AS482</td><td></td></tr><tr><td>Magnetic hot&amp;nbsp; stirrer</td><td>As one</td><td>RHS-1DN</td><td></td></tr><tr><td>Ceramic hotplate</td><td>As one</td><td>CHP-17DN</td><td></td></tr><tr><td>Spin coater</td><td>Kyowariken</td><td>K-359 S1</td><td></td></tr><tr><td>Vacuum pump</td><td>ULVAC</td><td>DA-30S</td><td></td></tr><tr><td>UV-O&lt;sub&gt;3&lt;/sub&gt; cleaner</td><td>Filgen</td><td>UV253E</td><td></td></tr><tr><td>Screen printer</td><td>Mitani Electronics</td><td>MEC-2400</td><td></td></tr><tr><td>Ultrasonic Soldering system</td><td>Kuroda Techno</td><td>SUNBONDER USM-5</td><td></td></tr><tr><td>Direct-current voltage and current source/monitor integrated system</td><td>San-Ei Electric</td><td>XES-40S1</td><td></td></tr><tr><td>Scanning electron microscope</td><td>JEOL Ltd.</td><td>JSM-7800</td><td></td></tr></tbody></table>

morphology control for fully printable organic&#8211;inorganic 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 material. However, fullerene derivatives are air-sensitive; therefore, air-stable material is needed as an alternative. In the present study, we propose and describe the properties of Ti-alkoxide as an alternative electron-accepting material to fullerene derivatives to create highly air-stable BHJ solar cells. It is well-known that controlling the morphology in the photoactive layer, which is constructed with fullerene derivatives as the electron acceptor, is important for obtaining a high overall efficiency through the solvent method. The conventional solvent method is useful for high-solubility materials, such as fullerene derivatives. However, for Ti-alkoxides, the conventional solvent method is insufficient, because they only dissolve in specific solvents. Here, we demonstrate a new approach to morphology control that uses the molecular bulkiness of Ti-alkoxides without the conventional solvent method. That is, this method is one approach to obtain highly efficient, air-stable, organic-inorganic bulk-heterojunction solar cells.

We have presented a protocol for fabricating fully printable organic-inorganic BHJ solar cells, as well as a method for controlling the phase-separation structure. The solar-cell performance has been extensively investigated27-31 when Ti(IV) isopropoxide and ethoxide were used as electron-accepting materials (Figure 1). These solar cells exhibited a short-circuit current density (Jsc) that is approximately eight times higher than that of devices using the &#34;...

Watch this Scientific Journal Video about Morphology Control for Fully Printable Organicâ€“Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer at JoVE.com

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

A method for fully printable, fullerene-free, highly air-stable, bulk-heterojunction solar cells based on Ti alkoxides as the electron acceptor and the electron-donating polymer fabrication is described here. Moreover, a method for controlling the morphology of the photoactive layer through the molecular bulkiness of the Ti-alkoxide units is reported.

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

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Research

JoVE Journal

Engineering

9.0K Views.  National Institute of Technology, Oyama College.  Een methode voor het volledig gedrukt te worden, fullereen-vrij, zeer lucht-stabiele, bulk-heterojunctie zonnecellen op basis van Ti alkoxiden als het elektron acceptor en het elektronen donerende polymeer fabricage wordt hier beschreven. Bovendien wordt een werkwijze voor het regelen van de morfologie van de fotoactieve laag door de moleculaire grote omvang van de Ti-alkoxide eenheden gerapporteerd. 

Video: Morphology Control for Fully Printable Organic–Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

Ambient Method for the Production of an Ionically Gated Carbon Nanotube Common Cathode in Tandem Organic Solar Cells

A method of fabricating organic photovoltaic (OPV) tandems that requires no vacuum processing is presented. These devices are comprised of two solution-processed polymeric cells connected in parallel by a transparent carbon nanotubes (CNT) interlayer. This structure includes improvements in fabrication techniques for tandem OPV devices. First the need for ambient-processed cathodes is considered. The CNT anode in the tandem device is tuned via ionic gating to become a common cathode. Ionic gating employs electric double layer charging to lower the work function of the CNT electrode. Secondly, the difficulty of sequentially stacking tandem layers by solution-processing is addressed. The devices are fabricated via solution and dry-lamination in ambient conditions with parallel processing steps. The method of fabricating the individual polymeric cells, the steps needed to laminate them together with a common CNT cathode, and then provide some representative results are described. These results demonstrate ionic gating of the CNT electrode to create a common cathode and addition of current and efficiency as a result of the lamination procedure.

A method of fabricating, in ambient conditions, organic photovoltaic tandem devices in a parallel configuration is presented. These devices feature an air-processed, semi-transparent, carbon nanotube common cathode.

A method of fabricating organic photovoltaic (OPV) tandems that requires no vacuum processing is presented. These devices are comprised of two ...

Integration of Light Trapping Silver Nanostructures in Hydrogenated Microcrystalline Silicon Solar Cells by Transfer Printing

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly known as plasmonic effects, play an important role. Research in this field has, however, been impeded owing to the difficulty of fabricating devices containing the desired functional metal nanostructures. In order to provide a viable strategy to this issue, we herein show a transfer printing-based approach that allows the quick and low-cost integration of designed metal nanostructures with a variety of device architectures, including solar cells. Nanopillar poly(dimethylsiloxane) (PDMS) stamps were fabricated from a commercially available nanohole plastic film as a master mold. On this nanopatterned PDMS stamps, Ag films were deposited, which were then transfer-printed onto block copolymer (binding layer)-coated hydrogenated microcrystalline Si (&#181;c-Si:H) surface to afford ordered Ag nanodisk structures. It was confirmed that the resulting Ag nanodisk-incorporated &#181;c-Si:H solar cells show higher performances compared to a cell without the transfer-printed Ag nanodisks, thanks to plasmonic light trapping effect derived from the Ag nanodisks. Because of the simplicity and versatility, further device application would also be feasible thorough this approach.

A viable transfer printing-based methodology to introduce plasmonic metal nanostructures in solar cells is described. Using nanopillar poly(dimethylsiloxane) stamps, an Ag-based ordered nanodisk array was integrated with standard hydrogenated microcrystalline Si solar cells, which led to improved device performances due to plasmonic light trapping.

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly ...

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 have used devices prepared by spin coating, a process that is not amenable to large-scale fabrication. This mismatch in device fabrication makes it difficult to translate quantitative results obtained in the laboratory to the commercial level, making optimization difficult. Using a mini-slot die coater, this mismatch can be resolved by translating the commercial process to the laboratory and characterizing the structure formation in the active layer of the device in real time and in situ as films are coated onto a substrate. The evolution of the morphology was characterized under different conditions, allowing us to propose a mechanism by which the structures form and grow. This mini-slot die coater offers a simple, convenient, material efficient route by which the morphology in the active layer can be optimized under industrially relevant conditions. The goal of this protocol is to show experimental details of how a solar cell device is fabricated using a mini-slot die coater and technical details of running in situ structure characterization using the mini-slot die coater.

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

Here, we present a protocol to fabricate organic thin film solar cells using a mini-slot die coater and related in-line structure characterizations using synchrotron scattering techniques.

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 environmentally damaging with lower processing temperatures presenting a viable and low cost alternative to conventional production. This paper further enhances these environmental credentials by evaluating the digital printing and therefore additive production route for these cells. This is achieved here by investigating the formation and performance of a metal oxide photoelectrode using nanoparticle sized titanium dioxide. An ink-jettable material was formulated, characterized and printed with a piezoelectric inkjet head to produce a 2.6 &#181;m thick layer. The resultant printed layer was fabricated into a functioning cell with an active area of 0.25 cm2 and a power conversion efficiency of 3.5%. The binder-free formulation resulted in a reduced processing temperature of 250 &#176;C, compatible with flexible polyamide substrates which are stable up to temperatures of 350 &#730;C. The authors are continuing to develop this process route by investigating inkjet printing of other layers within dye sensitized solar cells.

This paper investigates the suitability of inkjet printing for the manufacturing of dye-sensitized solar cells. A binder-free TiO2 nanoparticle ink was formulated and printed onto a FTO glass substrate. The printed layer was fabricated into a cell with an active area of 0.25 cm2 and an efficiency of 3.5%.

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

Fabrication of Fully Solution Processed Inorganic Nanocrystal Photovoltaic Devices

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal inks. For the photoactive absorber layer, colloidal CdTe and CdSe nanocrystals (3-5 nm) are synthesized using an inert hot injection technique and cleaned with precipitations to remove excess starting reagents. Similarly, gold nanocrystals (3-5 nm) are synthesized under ambient conditions and dissolved in organic solvents. In addition, precursor solutions for transparent conductive indium tin oxide (ITO) films are prepared from solutions of indium and tin salts paired with a reactive oxidizer. Layer-by-layer, these solutions are deposited onto a glass substrate following annealing (200-400 &#176;C) to build the nanocrystal solar cell (glass/ITO/CdSe/CdTe/Au). Pre-annealing ligand exchange is required for CdSe and CdTe nanocrystals where films are dipped in NH4Cl:methanol to replace long-chain native ligands with small inorganic Cl- anions. NH4Cl(s) was found to act as a catalyst for the sintering reaction (as a non-toxic alternative to the conventional CdCl2(s) treatment) leading to grain growth (136&#177;39 nm) during heating. The thickness and roughness of the prepared films are characterized with SEM and optical profilometry. FTIR is used to determine the degree of ligand exchange prior to sintering, and XRD is used to verify the crystallinity and phase of each material. UV/Vis spectra show high visible light transmission through the ITO layer and a red shift in the absorbance of the cadmium chalcogenide nanocrystals after thermal annealing. Current-voltage curves of completed devices are measured under simulated one sun illumination. Small differences in deposition techniques and reagents employed during ligand exchange have been shown to have a profound influence on the device properties. Here, we examine the effects of chemical (sintering and ligand exchange agents) and physical treatments (solution concentration, spray-pressure, annealing time and annealing temperature) on photovoltaic device performance.

This protocol describes the synthesis and solution deposition of inorganic nanocrystals layer by layer to produce thin film electronics on non-conductive surfaces. Solvent-stabilized inks can produce complete photovoltaic devices on glass substrates via spin and spray coating following post-deposition ligand exchange and sintering.

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal ...

Influence of Hybrid Perovskite Fabrication Methods on Film Formation, Electronic Structure, and Solar Cell Performance

Hybrid organic/inorganic halide perovskites have lately been a topic of great interest in the field of solar cell applications, with the potential to achieve device efficiencies exceeding other thin film device technologies. Yet, large variations in device efficiency and basic physical properties are reported. This is due to unintentional variations during film processing, which have not been sufficiently investigated so far. We therefore conducted an extensive study of the morphology and electronic structure of a large number of CH3NH3PbI3 perovskite where we show how the preparation method as well as the mixing ratio of educts methylammonium iodide and lead(II) iodide impact properties like film formation, crystal structure, density of states, energy levels, and ultimately the solar cell performance.

We present an extensive study on the effects of different fabrication methods for organic/inorganic perovskite thin films by comparing crystal structures, density of states, energy levels, and ultimately the solar cell performance.

Hybrid organic/inorganic halide perovskites have lately been a topic of great interest in the field of solar cell applications, with the potential to ...

Chemistry

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 properties. The possibility of doping was investigated by adding monovalent cation halides with similar ionic radii to Pb2+, including Cu+, Na+, and Ag+. A shift in the Fermi level and a remarkable decrease of sub-bandgap optical absorption, along with a lower energetic disorder in the perovskite, was achieved. An order-of-magnitude enhancement in the bulk hole mobility and a significant reduction of transport activation energy within an additive-based perovskite device was attained. The confluence of the aforementioned improved properties in the presence of these cations led to an enhancement in the photovoltaic parameters of the perovskite solar cell. An increase of 70 mV in open circuit voltage for AgI and a 2 mA/cm2 improvement in photocurrent density for NaI- and CuBr-based solar cells were achieved compared to the pristine device. Our work paves the way for further improvements in the optoelectronic quality of CH3NH3PbI3 perovskite and subsequent devices. It highlights a new avenue for investigations on the role of dopant impurities in crystallization and controls the electronic defect density in perovskite structures.

Monovalent Cation Doping of CH3NH3PbI3 for Efficient Perovskite Solar Cells

Here, we present a protocol to adjust the properties of solution-processed CH3NH3PbI3 through the incorporation of monovalent cation additives in order to achieve highly 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 ...

Well-aligned Vertically Oriented ZnO Nanorod Arrays and their Application in Inverted Small Molecule Solar Cells

This manuscript describes how to design and fabricate efficient inverted solar cells, which are based on a two-dimensional conjugated small molecule (SMPV1) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), by utilizing ZnO nanorods (NRs) grown on a high quality Al-doped ZnO (AZO) seed layer. The inverted SMPV1:PC71BM solar cells with ZnO NRs that grew on both a sputtered and sol-gel processed AZO seed layer are fabricated. Compared with the AZO thin film prepared by the sol-gel method, the sputtered AZO thin film exhibits better crystallization and lower surface roughness, according to X-ray diffraction (XRD) and atomic force microscope (AFM) measurements. The orientation of the ZnO NRs grown on a sputtered AZO seed layer shows better vertical alignment, which is beneficial for the deposition of the subsequent active layer, forming better surface morphologies. Generally, the surface morphology of the active layer mainly dominates the fill factor (FF) of the devices. Consequently, the well-aligned ZnO NRs can be used to improve the carrier collection of the active layer and to increase the FF of the solar cells. Moreover, as an anti-reflection structure, it can also be utilized to enhance the light harvesting of the absorption layer, with the power conversion efficiency (PCE) of solar cells reaching 6.01%, higher than the sol-gel based solar cells with an efficiency of 4.74%.

This manuscript describes how to design and fabricate efficient inverted SMPV1:PC71BM solar cells with ZnO nanorods (NRs) grown on a high quality Al-doped ZnO (AZO) seed layer. The well-aligned vertically oriented ZnO NRs exhibit high crystalline properties. The power conversion efficiency of solar cells can reach 6.01%.

This manuscript describes how to design and fabricate efficient inverted solar cells, which are based on a two-dimensional conjugated small molecule ...

Flash Infrared Annealing for Perovskite Solar Cell Processing

Organic&#8211;inorganic perovskites have an impressive potential for the design of next generation solar cells and are currently considered for upscaling and commercialization. Currently, perovskite solar cells rely on spin-coating which is neither practical for large areas nor environmentally friendly. Indeed, one of the conventional and most effective lab-scale methods to induce perovskite crystallization, the antisolvent method, requires an amount of toxic solvent that is difficult to apply on larger surfaces. To solve this problem, an antisolvent-free and rapid thermal annealing process called flash infrared annealing (FIRA) can be used to produce highly crystalline perovskite films. The FIRA oven is composed of an array of near-infrared halogen lamps with an illumination power of 3,000 kW/m2. A hollow aluminum body enables an effective water-cooling system. The FIRA method allows the synthesis of perovskite films in less than 2 s, achieving efficiencies &#62;20%. FIRA has a unique potential for the industry because it can be adapted to continuous processing, is antisolvent-free, and does not require lengthy, hour-long annealing steps.

We describe a flash infrared annealing method used for the synthesis of perovskite and mesoscopic-TiO2 films. Annealing parameters are varied and optimized for processing on fluorine-doped tin oxide (FTO) glass and indium tin oxide-coated polyethylene terephthalate (ITO PET), subsequently giving devices power conversion efficiencies &#62;20%.

Organic&#8211;inorganic perovskites have an impressive potential for the design of next generation solar cells and are currently considered for upscaling ...

Environment

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.

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 ...

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

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