Asmat Ullah
Asmat Ullah
PhD
Photovoltaics, Perovskite solar cell, Tandem solar cell
About
22
Publications
16,074
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Introduction
Asmat Ullah currently works at the Division of photovoltaics, Korea Institute of Energy Research. Their current project is 'Perovskite Solar Cells for Tandem Applications'.
Publications
Publications (22)
Here, MgxCe1−xO2 (where x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05) nanostructures have been successfully synthesized by using a simple, easy, and cost-effective soft chemical method. X-ray diffraction (XRD) patterns substantiate the single-phase formation of a CeO2 cubic fluorite structure for all samples. Infrared spectroscopy results depict the p...
Perovskite solar cells (PSCs) have witnessed a meteoric rise in device performance. However, maintaining photostability, particularly under thermal stress, remains a challenge due to defect formation in the perovskite layer. This study introduces europium (III) trifluoromethanesulfonate [Eu(OTF)3] as a multifunctional additive in two‐step processed...
To demonstrate flexible and tandem device applications, a low‐temperature Cu2ZnSnSe4 (CZTSe) deposition process, combined with efficient alkali doping, was developed. First, high‐quality CZTSe films were grown at 480 °C by a single co‐evaporation, which is applicable to polyimide (PI) substrate. Because of the alkali‐free substrate, Na and K alkali...
Inverted type perovskite solar cells (PSCs) have recently emerged as a major focus in academic and industrial photovoltaic research. Their multiple advantages over conventional PSCs include easy processing, hysteresis‐free behavior, high stability, and compatibility for tandem applications. However, the maximum power conversion efficiency (PCE) of...
Dual-band electrochromic smart windows can dynamically and independently control near infrared (NIR) and visible (Vis) light, and are considered a promising technology for improving building energy efficiency. However, most existing dual band electrochromic materials consist of complex nanocomposites, and it is difficult to balance the delicate com...
Perovskite Solar Cells
In article number 2103175, Young S. Park, Sungjun Hong and co-workers design a halogenated phenothiazine based self-assembled monolayer as a new type of hole transporting layer in inverted perovskite solar cells, displaying an energetically well aligned interface with the light absorbing perovskite top layer. The advantage of...
A breakthrough in the N,N-dimethylformamide (DMF) molecular ink route for fabricating highly efficient, low bandgap CuIn(S,Se) 2 (CISSe) solar cells is presented, demonstrating a newly certified record efficiency of 14.4% from air-processed devices. This finding changes the previous recognition of the requirement of a controlled environment, i.e.,...
Perovskite solar cells (PSC) has shown a rapid rise in the device performance in recent years but it is still far from commercialization due to challenges like long-term stability. The role of charge selective contacts (CSC) and the interfaces between perovskite and CSC plays a crucial role in device stability. Therefore, we designed a hole selecti...
Recent advances in perovskite solar cells (PSCs) performance have been closely related to improved interfacial engineering and charge selective contacts. Here, a novel and cost‐competitive phenothiazine based, self‐assembled monolayer (SAM) as a hole‐selective contact for p‐i‐n PSCs is introduced. The molecularly tailored SAM enables an energetical...
The role of ferromagnetic cobalt tetraoxide (Co3O4) nanoparticles’ addition in (Cu0.5Tl0.5) Ba2Ca2Cu3O10-δ (CuTl-1223) superconductor was investigated via infield transport properties measurements. The solgel method was used for synthesis of Co3O4 nanoparticles and CuTl-1223 superconducting phase was prepared by solid-state reaction method. These C...
A scalable photoelectrochromic (PEC) glass which can be darkened on exposure to sunlight and return to its original clear state in the absence of sunlight without any expensive materials like ruthenium dye or transparent conductive oxide was fabricated. The PEC glass is composed of light absorbing layer of ligand attached titanium oxide, color chan...
A gel electrolyte based on a metal-organic framework (MOF), comprised of Al³⁺ and trimesic acid, was used in dye-sensitized solar cells. The electrolyte was gelated inside the solar cell to ensure the best interfacial connection between the TiO2 photoanode and electrolyte ingredients. The photovoltaic performance of the solar cells showed that the...
The defects present in the solution-processed perovskite light absorbing materials are responsible for deteriorating the performance and stability of perovskite solar cells. Therefore, suppressing of the defect formation and passivating the pre-existing defects in perovskite materials is of paramount importance in pushing the efficiency of perovski...
We examined the structural, magnetic, and dielectric properties of Co1-xMgxCr2O4 nanoparticles with composition x = 0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1 in detail. X-ray diffraction (XRD) revealed normal spinel structure for all the samples. Rietveld refinement fitting results of the XRD showed no impurity phases which signifies the formation of single...
Effect of silica (SiO 2) coating concentration on structural and magnetic properties of multiferroic cobalt chromite (CoCr 2 O 4) nanoparticles have been studied. The nanoparticles with average crystallite size in the range 19 to 28 nm were synthesised by sol-gel method. X-ray diffraction (XRD) analysis has verified the composition of single-phase...
We studied the temperature dependent magnetic properties of multiferroic cobalt chromite (CoCr2O4) nanoparticles. The X-ray diffraction revealed the cubic spinel structure of the nanoparticles. Raman and Fourier transform infrared spectroscopy confirmed the formation of single phase normal spinel for CoCr2O4. Transmission electron microscopy images...
Effects of non-magnetic Mg concentration on structure, dielectric and magnetic properties
of Co1-xMgxCr2O4 nanoparticles with composition (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) was
analyzed thoroughly. The nanoparticles of all compositions were synthesized by using solgel method. X-ray diffraction revealed normal spinel structure for all samples. The...
We reported systematic study on structural and magnetic properties of nickel/nickel oxide (Ni/NiO) nanoparticles annealed under air atmosphere at different temperatures in the range 400–800 °C. The XRD spectra revealed two phases such as Ni and NiO. The average crystallite size increases with increasing annealing temperature. A phase diagram was de...
Cerium dioxide (CeO2) is an important oxide with a broad range of applications which
include catalysis sorption, polishing agents, photonic and electronic devices, gas sensing and
solid oxide fuel cells (SOFC). Undoped and Mg-doped ceria nanostructures have been
successfully synthesized using simple, easy, environmental friendly and cost effective...
Questions
Questions (15)
I seek help for perovskite UPS analysis for the Valence band and work function calculation. The sample preparation and if there are any critical things?
I have characterized my perovskite layer several times in different architectures; (Glass/Perovskite), (ITO/perovskite), (ITO/PTAA/Perovskite).
My SECO is in the range of 16.87eV but the valence band cut off is always higher (~1.6eV). The perovskite Eg~1.56eV. With these values, the Fermi level is above conduction band. I would appreciate your help in this regard. Thank you.
- My device architecture is (ITO/NiOx/CsFAMA/PCBM/Ag). I have attached the dark and under illumination JV curves.
- I have prepared the devices several times. the average Jsc <6, Voc~0.9, FF~0.2.
- JV curves are S-shaped.
- Looking forward to getting some insight especially for the low Jsc and FF problem. Thank you!
I am using PEDOT:PSS as Hole transport material in perovskite solar cell, is there any method (any easy software or some theoretical means) by which I can find the expected change in the band gap with doping, before doing experiment. So, to design my experiment more efficiently? Thank you.
what is the motivation of inverted PIN structure over planner NIP structure in terms of efficiency, stability, low temperature and cost etc? Which is more suitable to make tandem with Silicon solar cell? or both, the NIP and PIN structures can make tandem with Silicon solar cells? Thank you.
can anyone please provide any reading material about the working principle of d33 meter and impedance analyzer? Thank You !
The figure and the details are in attachment. Thank you.
Best regards,
Asmat
It is well known that materials show better piezoelectric properties at MPB. But why mostly piezoelectric single crystals are away from MPB composition?
Why sometimes its not easy to make piezoelectric single crystals with MPB composition?
Thank you!
In textured ceramics, instead of Mol.% or Weight% mostly people used 10 or 20 Volume % template. Anybody can explain how to calculate volume%. Please!!
Thank You.
I am working on texturing of PZT, but there is not much literature available for it. And why the PZT composition with Zr rich hinders the texturing? Thank you.
Which material system has the possibility to have this phenomenon? (Do we have this phenomenon in BaTiO3?) What is the possible explanation?
intensities of peaks (111) (400) (422) (511) significantly increases with increasing the Mg doping concentration, why is so? any refrence to study please?
We have undoped, 1,2 ,3,4 and 5% Mg doped Ceria nanostructures. in its dielectric results (using LCR meter), the AC conductivity is nearly constant at low frequencies and then increases above a certain characteristic point with increase in frequency.
The AC measurements were carried out using LCR meter at room temperature in the frequency range of 0 kHz to 5MHz. The dielectric constant (ε’) was calculated from the equation.
ε' = (t×Cp) / (A×εo)
Where t is thickness of the pellets, Cp is the equivalent parallel capacitance obtained experimentally, A is the area of the pellets and εo is permittivity of vacuum. The dielectric loss (ε”) was calculated from the multiplication of ε_ with the dissipation factor D obtained experimentally. Finally, the AC conductivity was calculated from the equation
σac = 2πfεoε_tanδ, where tanδ = ε”/ ε’
How does AC conductivity of CeO2 nanostructures increase with increasing Mg doping concentration levels. Can anybody please answer with references?
we have prepared Mg doped ceria nanostructures, and characterized by LCR meter for electrical conductivity, at low frequencies the electric conductivity is almost same for all Mg dopant levels but electrical conductivity increases at higher frequencies with higher doping level of Mg.
and with increase in electrical conductivity in high Mg dopant level, Reactive oxygen species (ROS) is also increased, can anybody explain what could be the possible reason for it?
We have undoped, 1,2 ,3,4 and 5% Mg doped Ceria nanostructures. in its dielectric results (using LCR meter), the AC conductivity is nearly constant at low frequencies and then increases above a certain characteristic point with increase in frequency.
The AC measurements were carried out using LCR meter at room temperature in the frequency range of 0 kHz to 5MHz. The dielectric constant (ε’) was calculated from the equation.
ε' = (t×Cp) / (A×εo)
Where t is thickness of the pellets, Cp is the equivalent parallel capacitance obtained experimentally, A is the area of the pellets and εo is permittivity of vacuum. The dielectric loss (ε”) was calculated from the multiplication of ε_ with the dissipation factor D obtained experimentally. Finally, the AC conductivity was calculated from the equation
σac = 2πfεoε_tanδ, where tanδ = ε”/ ε’
How does AC conductivity of CeO2 nanostructures increase with increasing Mg doping concentration levels. Can anybody please answer with references?
