Browsing by Author "Akrema"

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Citation - WoS: 1
Citation - Scopus: 1
Light-Controlled Electrostatic Self-Assembly of Quantum Dots
(Amer Chemical Soc, 2025) Akrema; Phul, Ruby; Yazici, Ahmet Faruk; Senel, Zeynep; Erdem, Talha
Electrostatic self-assembly is one of the important self-assembly mechanisms that found use in optoelectronics. Although this method enables realizing unconventional architectures, producing complicated architectures in large areas requires local control over the self-assembly process. One of the ways to achieve this control is to provide enough kinetic energy to the self-assembling nanoparticles so that they can escape electrostatic attraction. We hypothesize that this energy can be delivered to the nanoparticles by treating them with light that can be absorbed by the particles. Here, we test this idea to tailor the electrostatic self-assembly of semiconductor quantum dots (QDs) using a laser. Employing fluorescence and atomic force microscopy, we demonstrate that the QDs are not attached to the substrate in regions where they are exposed to light while they are coated in the absence of optical excitation. We further conduct theoretical analysis to show that elevated temperatures indeed allow the QDs to escape the electrostatic attraction of the charged polymers on the surface. We also demonstrate that increasing the temperature during the coating process without irradiating the sample gives similar results as the case when the sample was irradiated. Finally, we fabricate an uncoated region on the self-assembled QD film with dimensions of similar to 200 mu m x 0.5 cm to demonstrate the feasibility of our approach to control the bottom-up self-assembly. We believe that our results may pave the way for a cost-effective and sustainable approach for the fabrication of nanoelectronic and optoelectronic devices.
Synchrotron-Based Techniques for Analysis of Perovskite Solar Cells
(Wiley-Blackwell, 2021) Farooq, Umar; Phul, Ruby; Shabbir, Mohd; Arif, Rizwan; Akrema
Perovskite solar cells (PSCs) have been proven as promising material, owing to their remarkable performance attained in the field of photovoltaic (PV) and optoelectronics. These materials possess direct band gaps, high absorption coefficient, low exciton binding energy, and long carrier diffusion lengths. However, the primary electronic structure, size and spatial distribution, and other significant properties of perovskite materials are not fully understood due to a lack of precise and high-spatiotemporal resolution characterization techniques. A synchrotron provides high-brilliance X-ray beams that can easily penetrate deeper into the matter to explore the material's properties at the atomic or molecular level within a short time. Herein, we discuss synchrotron techniques for determining the structure and properties of perovskite materials within the bulk, at the surfaces and the interfaces. This chapter is dedicated to providing the latest findings on developing synchrotron-based techniques tailored for PSC. The method of characterization is also discussed with sample preparation. Finally, we focused on the state-of-the-art strategies for gaining in-depth knowledge of mechanism enhancing the photovoltaic performance and providing decisive answers to the outstanding science problems in the perovskite field, pushing forward technological development. © 2022 Elsevier B.V., All rights reserved.