Study of interface chemistry between the carrier-transporting layers and their influences on the stability and performance of organic solar cells

Hilal, Muhammad,Han, Jeong In Springer-Verlag 2018 Applied nanoscience Vol.8 No.6

The effect of the functionalization of multiple carrier transporting interlayers on the performance and stability of bulk heterojunction organic solar cells

Hilal, Muhammad,Han, Jeong In Springer-Verlag 2018 Journal of materials science Materials in electron Vol.29 No.16

Improving the conductivity of PEDOT:PSS to nearly 1 million S/m with graphene on an ITO-glass substrate

Hilal, Muhammad,Han, Jeong In Elsevier 2018 Synthetic metals Vol.245 No.-

<P><B>Abstract</B></P> <P>In this study, we effectively improved the electrical conductivity of poly(ethylene-3,4-dioxythiophene):poly (styrenesulphonic acid) (PEDOT:PSS) thin film by introducing various concentrations of our highly conductive synthesized graphene. The electrical conductivity of the PEDOT:PSS was enhanced from 597418.17 to 899076.24 S/m when a 2 mg/ml concentration of graphene was added to the PEDOT:PSS. However, the addition of graphene in excess (2.5 mg/ml) decreased the conductivity to 719130.49 S/m, which might have been because of further defects being generated in the film that obstructed the fast transport of charge carriers to the current probes of the four-point probe. X-ray diffraction pattern, Raman spectroscopy and X-ray photoelectron spectroscopy analyses suggest that the graphene-PEDOT:PSS composite contained various kinds of chemical functionalizations that provided an additional pathway in the form of cross-linking bridges for the very quick transport of free charge carriers from the voltage probe to the current probe, resulting in enhanced carrier mobility.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Significantly improvement in the electrical conductivity of PEDOT:PSS via the addition of highly conductive synthesized G. </LI> <LI> The enhancement in conductivity is due to the chemical bond formation at the interface of G-PEDOT: PSS composite thin film. </LI> <LI> Those chemical bonds provide an additional pathway for the quick charge movement inside the G-PEDOT:PSS composite film. </LI> <LI> The synthesized G doped PEDOT:PSS composite (G-PEDOT:PSS) is a suitable option to use as an HTL in the field of photonics. </LI> </UL> </P>

Significant improvement in the photovoltaic stability of bulk heterojunction organic solar cells by the molecular level interaction of graphene oxide with a PEDOT: PSS composite hole transport layer

Hilal, Muhammad,Han, Jeong In Elsevier 2018 Solar energy Vol.167 No.-

<P><B>Abstract</B></P> <P>In this paper, we report on the use of molecular level interaction between a composite poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) and graphene oxide (GO) hole transport layer (HTL) to improve the long term stability and performance of poly(3-hexylthiophene): poly(3-hexylthiophene): 3′H-cyclopropa [8,25] [5,6] fullerene-C60-D5h(6)-3′-butanoic acid 3′-phenyl methyl ester (P3HT: PCBM)-based bulk heterojunction organic solar cells (OSCs). The device employing this composite HTL demonstrated a maximum power conversion efficiency (PCE) of 4.82% with good reproducibility and retained over 30% of its initial PCE without encapsulation after 15 days under atmospheric conditions. This was a significant improvement compared with devices fabricated with either single GO or PEDOT: PSS HTLs, which retained only 26% and 0% of their initial PCE values of 3.16% and 4.00%, respectively. Hence, we imagine that this air resistant HTL composite will probably contribute significantly to the widespread commercialization of low cost and easily fabricated OSCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effect of different HTLs on the stability and performance of organic solar cells. </LI> <LI> GO/PEDOT:PSS HTL shows an improvement in stability and PCE over bare GO or PEDOT:PSS. </LI> <LI> The improvement is due to the bond formation at the interface of GO/PEDOT:PSS HTL. </LI> <LI> The study is paving a way for a new technique to improve the stability of OSCs. </LI> </UL> </P>

A dual-functional flexible sensor based on defects-free Co-doped ZnO nanorods decorated with CoO clusters towards pH and glucose monitoring of fruit juices and human fluids

Hilal Muhammad,양우철 나노기술연구협의회 2022 Nano Convergence Vol.9 No.14

Herein, ZnO nanorods were doped with Co and decorated with CoO clusters through an in situ technique to create a CoO/Co-doped ZnO (CO/CZO) heterostructure at low temperatures (150 °C) on a flexible PET substrate. In the CO/CZO heterostructure, the Co dopant has a low energy barrier to substitute Zn atoms and adsorb over oxygen atoms and their vacancies. Therefore, it decreased the charge density (ND = 2.64 × 1019 cm−3) on non-active sites of ZnO and lowered the charge transfer resistance (317 Ω) at Co-doped-ZnO/electrolyte interface by suppressing the native defects and reducing the Schottky barrier height (− 0.35 eV), respectively. Furthermore, CoO clusters induced a p-n heterostructure with Co-doped ZnO, prevented corrosion, increased the active sites for analyte absorption, and increased the ultimate tensile strength (4.85 N m−2). These characteristics enabled the CO/CZO heterostructure to work as a highly sensitive, chemically stable, and flexible pH and glucose oxidation electrode. Therefore, CO/CZO heterostructure was explored for pH monitoring in human fluids and fruit juices, demonstrating a near-Nernst-limit pH sensitivity (52 mV/pH) and fast response time (19 s) in each human fluid and fruit juice. Also, it demonstrated high sensitivity (4656 µM mM−1 cm−2), low limit of detection (0.15 µM), a broad linear range (0.04 mM to 8.85 mM) and good anti-interference capacity towards glucose-sensing. Moreover, it demonstrated excellent flexibility performances, retained 53% and 69% sensitivity of the initial value for pH and glucose sensors, respectively, after 500 bending, stretching, and warping cycles.

Interface engineering of G-PEDOT: PSS hole transport layer via interlayer chemical functionalization for enhanced efficiency of large-area hybrid solar cells and their charge transport investigation

Hilal, Muhammad,Han, Jeong In Elsevier 2018 SOLAR ENERGY -PHOENIX ARIZONA THEN NEW YORK- Vol.174 No.-

<P><B>Abstract</B></P> <P>In this study, in order to minimize the recombination current of free charge carriers in a large-area organic-inorganic hybrid solar cell (O-IHSCs), we improved the electrical conductivity of a graphene (G) and poly(3,4-ethylenedioxy thiophene)–poly(styrenesulfonate) (G-PEDOT:PSS) hole transport layer (HTL) by introducing various concentrations of synthesized graphene (G) into poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The electrical conductivity of G-PEDOT:PSS was enhanced to 932781.17 S m<SUP>−1</SUP> via the addition of 2 mg/mL of G to PEDOT:PSS. The O-IHSCs fabricated with the highly conductive G-PEDOT:PSS composite as HTL enhanced the power conversion efficiency (PCE) to 3.90%, a 70% increase compared to O-IHSCs fabricated with pristine PEDOT:PSS HTL. However, the accumulation of G at a higher concentration (2.5 mg/mL) degrades the performance of the solar cell, which generated further defects or film aggregation, interfering with the fast transport of free charge carriers toward their respective electrodes. The G-PEDOT:PSS composite contained various types of functionalization via interfacial reaction between the G and PEDOT:PSS based on Raman and X-ray photoelectron spectroscopy studies. These chemical functionalizations provide an additional mechanism of charge transport via bridges enhancing the carrier mobility and suppression of recombination of free charge carriers, resulting in significant improvement in photovoltaic performance of the O-IHSCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Simple fabrication technique approached for hybrid solar cells (O-IHSCs). </LI> <LI> The interface of G-PEDOT:PSS composite HTL chemically functionalized. </LI> <LI> It enhances the electrical conductivity of G-PEDOT:PSS ~ 1 million (S/m). </LI> <LI> G-PEDOT:PSS composite HTL based O-IHSCs exhibit 3.90% of PCE. </LI> <LI> This Si/P3HT:PCBM/G-PEDOT:PSS interfaces may be recommended for commercial O-IHSCs. </LI> </UL> </P>

Fabrication and characterization of P3HT:PCBM based bulk heterojunction photoelectric cell

엄태훈,( Muhammad Hilal ),( Mehboob Alam ),한정인 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.0

Morpho-Anatomical Responses of Trigonella foenum graecum Linn. to Induced Cadmium and Lead Stress

( Syed Hilal Ahmad ),( Zafar Reshi ),( Javed Ahmad ),( Muhammad Iqbal ) 한국식물학회 2005 Journal of Plant Biology Vol.48 No.1

Effect of different concentrations of cadmium (0, 5, 15, 30, 50 ㎍/g of soil) and lead (0, 25, 50, 100, 200 ㎍/g of soil) on morphological and anatomical features of Trigonella foenum graecum Linn. was studied at pre-flowering, flowering and post flowering stages. Morphological attributes, like number of leaves per plant, total leaf area of the plant and single leaf area, dry mass of stem, root and leaf, length of shoot, root and plant, size of stomata and stomatal pore, and the density of stomata on both epidermises were significantly reduced under metal stress at all the developmental stages. Trichome length on both epidermises increased while their density decreased under metal stress. Under cadmium stress, proportion of pith and vasculature decreased but cortex increased in the stem. Under lead stress, proportion of pith and vasculature increased but cortex decreased in the stem. In the root, proportion of vasculature and pith increased and cortex decreased in response to both cadmium and lead stresses. Dimensions of vessel element and xylem fibre in the wood of stem and root decreased under the cadmium and lead stresses. Decrease in density of vessel element in the stem and root with advancement of age was more pronounced in plants grown under cadmium and lead stresses.

Identification of prokaryotic promoters and their strength by integrating heterogeneous features

Tayara, Hilal,Tahir, Muhammad,Chong, Kil To Elsevier 2020 Genomics Vol.112 No.2

<P><B>Abstract</B></P> <P>The promoter is a regulatory DNA region and important for gene transcriptional regulation. It is located near the transcription start site (TSS) upstream of the corresponding gene. In the post-genomics era, the availability of data makes it possible to build computational models for robustly detecting the promoters as these models are expected to be helpful for academia and drug discovery. Until recently, developed models focused only on discriminating the sequences into promoter and non-promoter. However, promoter predictors can be further improved by considering weak and strong promoter classification. In this work, we introduce a hybrid model, named iPSW(PseDNC-DL), for identification of prokaryotic promoters and their strength. It combines a convolutional neural network with a pseudo-di-nucleotide composition (PseDNC). The proposed model iPSW(PseDNC-DL) has been evaluated on the benchmark datasets and outperformed the current state-of-the-art models in both tasks namely promoter identification and promoter strength identification. The developed tool iPSW(PseDNC-DL) has been constructed in a web server and made freely available at https://home.jbnu.ac.kr/NSCL/PseDNC-DL.htm </P> <P><B>Highlights</B></P> <P> <UL> <LI> Computational predictor is developed for prediction of prokaryotic promoters and their strength. </LI> <LI> Deep learning approach is used. </LI> <LI> Integrating deep learning features with pseudo-di-nucleotide composition (PseDNC). </LI> <LI> Achieved promising outcomes than existing methods. </LI> </UL> </P>

Study of Graphene Oxide as the Multifunctional Interlayers for Conventional Polymer Solar Cells

엄태훈,( Muhammad Hilal ),한정인 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

In this study, we report the effects of graphene oxide as the multifunctional interfacial carrier transporting layers (CTLs) between the poly(3-hexylthiophene): poly(3-hexylthiophene): 3'H-cyclopropa [8,25] [5,6] fullerene-C60-D5h(6)-3'-butanoic acid 3'-phenyl methyl ester (P3HT:PCBM) layer and metal electrodes of organic solar cells. The composite of graphene oxide (GO) with zinc oxide (ZnO) (GO/ZnO) and with poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) (GO/PEDOT:PSS was produced by grafting the ZnO and PEDOT:PSS onto GO sheets using a molecular level interconnections approach. The cross-linking and longitudinal binding of GO with ZnO and with PEDOT:PSS demonstrated a significant improvement in PCE (4.88%), reproducibility and environmental stability (40% after 432 hr).