Fully-ambient-processed mesoscopic semitransparent perovskite solar cells by islands-structure-MAPbI_3-xCl_x-NiO composite and Al₂O₃/NiO interface engineering

Wang, Yousheng,Mahmoudi, Tahmineh,Yang, Hwa-Young,Bhat, Kiesar Sideeq,Yoo, Jin-Young,Hahn, Yoon-Bong Elsevier 2018 Nano energy Vol.49 No.-

<P><B>Abstract</B></P> <P>Perovskite solar cells (PSCs) because of low-cost fabrication and high performance have shown superb potential for the next-generation photovoltaic application. For the potential applications of photovoltaic technologies, semitransparent PSCs are also highly attractive and of commercial interest to develop building- and tandem-integrated solar cells. Here, we present fully-ambient-processed stable and mesoscopic semitransparent PSCs by non-continuous islands-structure-CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3-x</SUB>Cl<SUB>x</SUB>-NiO nanoparticles (MAPbI<SUB>3-x</SUB>Cl<SUB>x</SUB>-NiO NPs) composite and interface engineering by inserting Al<SUB>2</SUB>O<SUB>3</SUB>/NiO between TiO<SUB>2</SUB> and MAPbI<SUB>3-x</SUB>Cl<SUB>x</SUB>-NiO composite layers in a device configuration of FTO/c-TiO<SUB>2</SUB>/mp-TiO<SUB>2</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB>/NiO/islands-structure-MAPbI<SUB>3-x</SUB>Cl<SUB>x</SUB>-NiO /spiro-OMeTAD/Au. Except for the islands-structure-MAPbI<SUB>3-x</SUB>Cl<SUB>x</SUB>-NiO capping layer, a uniform and thicker and transparent TiO<SUB>2</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB>/NiO/MAPbI<SUB>3-x</SUB>Cl<SUB>x</SUB> composite layer is formed, which can effectively reduce photocurrent density loss and interface recombination. Interestingly, the optimized semitransparent PSCs showed hysteresis-free performance. The average visible transmittance (AVT) of MAPbI<SUB>3-x</SUB>Cl<SUB>x</SUB>-NiO NPs composite film was ranged from 18% to 56% and the corresponding device <I>PCE</I> changed from 17.51% to 12.47%. The PSCs without encapsulation showed an excellent air stability over 270 days with retaining ~98% of its original <I>V</I> <SUB> <I>oc</I> </SUB>, ~96% of <I>J</I> <SUB> <I>sc</I> </SUB>, ~97% of <I>FF</I> and ~93% of <I>PCE</I> under ambient condition (25–30 ℃ and 45–50% humidity). Finally, we achieved semitransparent device of <I>PCE</I> = 10.06%, corresponding to AVT = 27%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Semitransparent PSCs based on islands-structure-MAPbI<SUB>3-x</SUB>Cl<SUB>x</SUB>-NiO composite and Al<SUB>2</SUB>O<SUB>3</SUB>/NiO interfacial engineering. </LI> <LI> Reduction of photocurrent loss and interface recombination by thick, semitransparent TiO<SUB>2</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB>/NiO/MAPbI<SUB>3-x</SUB>Cl<SUB>x</SUB>. </LI> <LI> Real semitransparent devices with <I>PCE</I>=10.06% and average visible transmittance of 27%. </LI> <LI> Excellent air-stability over 270 days with retaining more than 93% of performance parameters under ambient condition. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Conceptual illustration and performance of Mesoscopic Semitransparent Perovskite Solar Cells by Islands-structure-MAPbI<SUB>3-x</SUB>Cl<SUB>x</SUB>-NiO Composite and Al<SUB>2</SUB>O<SUB>3</SUB>/NiO Interface Engineering.</P> <P>[DISPLAY OMISSION]</P>

Air-stable, hole-conductor-free high photocurrent perovskite solar cells with CH₃NH₃PbI₃–NiO nanoparticles composite

Wang, Yousheng,Rho, Won-Yeop,Yang, Hwa-Young,Mahmoudi, Tahmineh,Seo, Seunghui,Lee, Dong-Heon,Hahn, Yoon-Bong Elsevier 2016 Nano energy Vol.27 No.-

<P><B>Abstract</B></P> <P>One of critical issues for practical applications of perovskite solar cells (PSCs) is how to enhance the photocurrent and air stability of the peovskite materials. Here, we report an air-stable, hole-conductor-free (HCF), high photocurrent PSC based on CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>–NiO nanoparticles (MAPbI<SUB>3</SUB>–NiO NPs) composite. The composite solution contains highly dispersed NiO NPs in solution of CH<SUB>3</SUB>NH<SUB>3</SUB>I(MAI) and PbI<SUB>2</SUB>in dimethylformamide. By introducing the CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>–NiO composite into the active layer, the HCF-PSCs with FTO/c-TiO<SUB>2</SUB>/mp-TiO<SUB>2</SUB>/MAPbI<SUB>3</SUB>–NiO/Au architecture have been fabricated under ambient conditions. This composite-based HCF-PSCs show a high photocurrent density (<I>J<SUB>sc</SUB> </I>) of 26.41mA/cm<SUP>2</SUP>, which is 97%of theoretical maximum (i.e., 27.2mA/cm<SUP>2</SUP>). Compared to the power conversion efficiency (PCE) of MAPbI<SUB>3</SUB>-based HCF-PSC (i.e., 5.43%), the MAPbI<SUB>3</SUB>–NiO NPs composite-based HCF-PSC showed a high PCE of 12.14%. This increase in PCE is mainly due to a remarkable increase in photocurrent density, suggesting that the MAPbI<SUB>3</SUB>–NiO composite enhances the charge carrier generation via improving photo-absorption and fast hole-conduction by NiO NPs. More interestingly, the composite-based HCF-PSCs without encapsulation showed remarkable air stability with retaining ~90% of its original PCE and ~94% of both <I>J<SUB>sc</SUB> </I> and FF for 60 days under ambient environment. XPS and IR spectra analysis revealed that Ni–O, Pb–O, C–O, Ni–N and N–NiO bonds attributed to strong chemical interaction between NiO and MAPbI<SUB>3</SUB> molecules enhance the air stability of MAPbI<SUB>3</SUB>–NiO composite based HCF-PSCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Air-stable, high photocurrent perovskite solar cells with CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>-NiO composites. </LI> <LI> Increase in photocurrent due to enhanced light harvesting and fast hole-conduction. </LI> <LI> Remarkable air stability with retaining 90–94 % of original devices performance. </LI> <LI> Strong chemical interaction between NiO and CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>, leading to air stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Conceptual illustration of air stable, hole-conductor-free high photocurrent perovskite solar cell based on CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>–NiO nanoparticles composites.</P> <P>[DISPLAY OMISSION]</P>

Ambient-air-solution-processed efficient and highly stable perovskite solar cells based on CH₃NH₃PbI_3−xCl_x-NiO composite with Al₂O₃/NiO interfacial engineering

Wang, Yousheng,Mahmoudi, Tahmineh,Rho, Won-Yeop,Yang, Hwa-Young,Seo, Seunghui,Bhat, Kiesar Sideeq,Ahmad, Rafiq,Hahn, Yoon-Bong Elsevier 2017 Nano energy Vol.40 No.-

<P><B>Abstract</B></P> <P>The poor air-stability and reproducibility of perovskite solar cells (PSCs) have prevented the practical applications of the devices that can withstand sustained operation under ambient air conditions. Here, we report all-ambient-air-solution-processed PSCs based on CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3−x</SUB>Cl<SUB>x</SUB>-NiO composite film with inserting Al<SUB>2</SUB>O<SUB>3</SUB>/NiO at the TiO<SUB>2</SUB>/perovskite interface in a cell configuration of FTO/c-TiO<SUB>2</SUB>/mp-TiO<SUB>2</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB>/NiO/MAPbI<SUB>3−x</SUB>Cl<SUB>x</SUB>-NiO/spiroOMeTAD/Au. The interface engineering with Al<SUB>2</SUB>O<SUB>3</SUB>/NiO not only improves crystalline quality of perovskite films and enhances charge transport, but also effectively suppresses carrier recombination. This composite-based interface engineering PSCs showed a high power conversion efficiency (<I>PCE</I>) of 18.14% and excellent reproducibility with average 16–18% <I>PCE</I> for 35 devices. More importantly, the devices without encapsulation showed a significant enhancement in long-term air-stability; the device photovoltaic parameters stabilized after 20 days and sustained its stability over 210 days with retaining ~100% of its original <I>V</I> <SUB> <I>oc</I> </SUB>, ~94% of <I>J</I> <SUB> <I>sc</I> </SUB>, ~91% of <I>FF</I> and ~86% of <I>PCE</I> in an ambient environment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ambient-air-solution-processed perovskite solar cells based on CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3−x</SUB>Cl<SUB>x</SUB>–NiO with Al<SUB>2</SUB>O<SUB>3</SUB>/NiO interface engineering. </LI> <LI> High quality and excellent crystallinity of MAPbI<SUB>3−x</SUB>Cl<SUB>x</SUB>–NiO composite film achieved by Al<SUB>2</SUB>O<SUB>3</SUB>/NiO interfacial engineering. </LI> <LI> High power conversion efficiency of 18.14%, small hysteresis and excellent reproducibility. </LI> <LI> Remarkable air-stability over 210 days with retaining ~100% of original <I>V<SUB>oc</SUB> </I>, ~94% of <I>J<SUB>sc</SUB> </I>, ~91% of <I>FF</I> and ~86% of <I>PCE</I>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>SEM image and long-term air stability of ambient-air-solution-processed PSCs based on CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3−x</SUB>Cl<SUB>x</SUB>-NiO composites with Al<SUB>2</SUB>O<SUB>3</SUB>/NiO interface engineering with FTO/c-TiO<SUB>2</SUB>/mp-TiO<SUB>2</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB>/NiO/ MAPbI<SUB>3−x</SUB>Cl<SUB>x</SUB>-NiO/Spiro-OMeTAD/Au configuration.</P> <P>[DISPLAY OMISSION]</P>

Graphene and its derivatives for solar cells application

Mahmoudi, Tahmineh,Wang, Yousheng,Hahn, Yoon-Bong Elsevier 2018 Nano energy Vol.47 No.-

<P><B>Abstract</B></P> <P>Graphene has played the role of game-changer for conductive transparent devices indebted to its unique two dimensional (2D) structures and gained an exceptional opportunity to be employed in energy industry. In the past two decades graphene has been merged with the concept of photovoltaic (PV) material and exhibited a significant role as a transparent electrode, hole/electron transport material and interfacial buffer layer in solar cell devices. This review covers the different methods of graphene fabrication and broadly discusses the recent advances in graphene-based solar cells, including bulk heterojunction (BHJ) organic, dye-sensitized and perovskite solar cell deices. The power conversion efficiency surpassed 20.3% for graphene-based perovskite solar cells and hit the efficiency of 10% for BHJ organic solar cells. Except the part of charge extracting and transport to the electrodes, graphene has another unique role of device protection against environmental degradation via its packed 2D network structure and provides long-term environmental stability for PV devices. We highlighted a comparative study on the role of graphene and its derivatives in photovoltaic devices. After all, the potential issues and the perspective for future research in graphene-based materials for PV applications are presented.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Key works related to graphene-based solar cells are reviewed and critically studied. </LI> <LI> Performance of graphene-based PVs is improved by functionalization, doping and oxidation. </LI> <LI> Flexibility of cells is improved with the use of graphene as transparent conductive electrode. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Schematic illustration of graphene and its derivatives for solar cells applications</P> <P>[DISPLAY OMISSION]</P>

Vitamin D Improves Intestinal Barrier Function in Cirrhosis Rats by Upregulating Heme Oxygenase-1 Expression

Peng-fei Wang,Dan-hua Yao,Yue-yu Hu,Yousheng Li 한국응용약물학회 2019 Biomolecules & Therapeutics(구 응용약물학회지) Vol.27 No.2

Intestinal barrier dysfunction always accompanies cirrhosis in patients with advanced liver disease and is an important contributor facilitating bacterial translocation (BT), which has been involved in the pathogenesis of cirrhosis and its complications. Several studies have demonstrated the protective effect of Vitamin D on intestinal barrier function. However, severe cholestasis leads to vitamin D depletion. This study was designed to test whether vitamin D therapy improves intestinal dysfunction in cirrhosis. Rats were subcutaneously injected with 50% sterile CCl4 (a mixture of pure CCl4 and olive oil, 0.3 mL/100 g) twice a week for 6 weeks. Next, 1,25(OH)2D3 (0.5 μg/100 g) and the vehicle were administered simultaneously with CCl4 to compare the extent of intestinal histologic damage, tight junction protein expression, intestinal barrier function, BT, intestinal proliferation, apoptosis, and enterocyte turnover. Intestinal heme oxygenase-1 (HO-1) expression and oxidative stress were also assessed. We found that vitamin D could maintain intestinal epithelial proliferation and turnover, inhibit intestinal epithelial apoptosis, alleviate structural damage, and prevent BT and intestinal barrier dysfunction. These were achieved partly through restoration of HO-1 and inhibition of oxidative stress. Taken together, our results suggest that vitamin D ameliorated intestinal epithelial turnover and improved the integrity and function of intestinal barrier in CCl4-induced liver cirrhotic rats. HO-1 signaling activation was involved in these above beneficial effects.

Coordinated Hospital-Home Fecal Microbiota Transplantation via Percutaneous Endoscopic Cecostomy for Recurrent Steroid-Dependent Ulcerative Colitis

( Xiaodong Ni ),( Shengxian Fan ),( Yongliang Zhang ),( Zhiming Wang ),( Lan Ding ),( Yousheng Li ),( Jieshou Li ) 대한소화기학회 2016 Gut and Liver Vol.10 No.6

Since its introduction as an alternative intestinal microbiota alteration approach, fecal microbiota transplantation (FMT) has been increasingly used as a treatment of choice for patients with ulcerative colitis (UC), but no reports exist regarding FMT via percutaneous endoscopic cecostomy (PEC). This report describes the case of a 24-year-old man with a 7-year history of recurrent, steroid-dependent UC. He received FMT via PEC once per day for 1 month in the hospital. After the remission of gastrointestinal symptoms, he was discharged from the hospital and continued FMT via PEC twice per week for 3 months at home. The frequency of stools decreased, and the characteristics of stools improved soon thereafter. Enteral nutrition was regained after 1 week, and an oral diet was begun 1 month later. Two months after the FMT end point, the patient resumed a normal diet, with formed soft stools once per day. The follow-up colonoscopy showed normal mucus membranes; then, the PEC set was removed. On the subsequent 12 months follow-up, the patient resumed orthobiosis without any gastrointestinal discomfort and returned to work. This case emphasizes that FMT via PEC can not only induce remission but also shorten the duration of hospitalization and reduce the medical costs; therefore, this approach should be considered an alternative option for patients with UC. (Gut Liver 2016;10:975-980)

Efficient bulk heterojunction hybrid solar cells with graphene-silver nanoparticles composite synthesized by microwave-assisted reduction

Mahmoudi, Tahmineh,Seo, Seunghui,Yang, Hwa-Young,Rho, Won-Yeop,Wang, Yousheng,Hahn, Yoon-Bong Elsevier 2016 Nano energy Vol.28 No.-

<P><B>Abstract</B></P> <P>Herein, we present a simple, eco-friendly one-step microwave-assisted reduction (MWAR) that can produce silver nanoparticles (Ag NPs) and reduced graphene oxide (rGO) in the form of Ag-rGO composites for application in heterojunction hybrid solar cells. The field-effect transistor fabricated with the MWAR Ag-rGO composite showed p-type behavior with a high mobility of 3.3×10<SUP>5</SUP> cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP> and conductivity of 9×10<SUP>6</SUP> S/m which is one-order of magnitude greater than pristine graphene (i.e., 1.59×10<SUP>5</SUP> S/m). As-synthesized Ag-rGO composite was introduced into the active layer of bulk heterojunction solar cell based on P3HT:PCBM. Compared to the P3HT:PCBM only device (i.e., control device), the Ag-rGO implemented device showed a power conversion efficiency (PCE) of 4.23%, which is about 42% increase over the control device (i.e. PCE=2.98%). This dramatic increase in PCE was found to be mainly due to an increase in short-circuit current (<I>J</I> <SUB>sc</SUB>) from 9.55 to 12.76mA/cm<SUP>2</SUP> (about 33% increase), suggesting that the incorporation of p-type Ag-rGO into the active layer enhances the charge carrier generation and fast extraction of holes to the electrode. Furthermore, the Ag-rGO composite based solar cells without encapsulation showed remarkable air stability with retaining ~90% of its original PCE and ~93% of <I>J</I> <SUB>sc</SUB> for 30 days under ambient environment, attributed to gas barrier feature of the randomly distributed graphene sheets.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Eco-friendly microwave-assisted reduction for graphene-silver (Ag-rGO) composite. </LI> <LI> Enhanced charge carrier generation and fast extraction of holes with Ag-rGO composite. </LI> <LI> Substantial enhancement of solar cells performance with P3HT:PCBM:Ag-rGO. </LI> <LI> Higher photocurrent and power conversion efficiency with the inclusion of Ag-rGO. </LI> <LI> Remarkable air stability without encapsulation of the Ag-rGO based hybrid solar cells. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Schematic illustration of a bulk heterojunction hybrid solar cell based on reduced graphene oxide (rGO)-silver nanoparticles (Ag-rGO) composite in the active layer. The Ag-rGO composite implemented device showed substantial enhancement of device performance, suggesting that the incorporation of Ag-rGO into the active layer enhances the charge carrier generation and fast extraction to the electrode. Furthermore, the Ag-rGO based solar cells without encapsulation showed remarkable air stability under ambient environment.</P> <P>[DISPLAY OMISSION]</P>

A Family of Magnetic Coupling DC–DC Converters With Zero-Voltage-Switching Over Wide Input Voltage Range and Load Variation

Guipeng Chen,Jie Dong,Yan Deng,Yong Tao,Xiangning He,Yousheng Wang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

This paper presents a family of soft-switching DC–DC converters with a simple auxiliary circuit consisting of a coupled winding and a pair of auxiliary switch and diode. The auxiliary circuit is activated in a short interval and thus the circulating conduction losses are small. With the auxiliary circuit, zero-voltage-switching (ZVS) and zero-current-switching are achieved for the main and auxiliary switches respectively, over wide input voltage range and load variation. In addition, the reverse-recovery problem of diodes is significantly alleviated because of the leakage inductor. Furthermore, the coupled inductor simultaneously serves as the main and auxiliary inductors, contributing to reduced magnetic component in comparison with the conventional zero-voltage-transition (ZVT) converters. Experimental results based on a 500 W prototype buck circuit validate the advantages and effectiveness of the proposed magnetic coupling ZVS converter.

A Family of Magnetic Coupling DC-DC Converters With Zero-Voltage-Switching Over Wide Input Voltage Range and Load Variation

Chen, Guipeng,Dong, Jie,Deng, Yan,Tao, Yong,He, Xiangning,Wang, Yousheng The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

This paper presents a family of soft-switching DC-DC converters with a simple auxiliary circuit consisting of a coupled winding and a pair of auxiliary switch and diode. The auxiliary circuit is activated in a short interval and thus the circulating conduction losses are small. With the auxiliary circuit, zero-voltage-switching (ZVS) and zero-current-switching are achieved for the main and auxiliary switches respectively, over wide input voltage range and load variation. In addition, the reverse-recovery problem of diodes is significantly alleviated because of the leakage inductor. Furthermore, the coupled inductor simultaneously serves as the main and auxiliary inductors, contributing to reduced magnetic component in comparison with the conventional zero-voltage-transition (ZVT) converters. Experimental results based on a 500 W prototype buck circuit validate the advantages and effectiveness of the proposed magnetic coupling ZVS converter.