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5 results on '"Sudhi Mahadevan"'

1. Assessing intra- and inter-molecular charge transfer excitations in non-fullerene acceptors using electroabsorption spectroscopy

Author

Sudhi Mahadevan, Taili Liu, Saied Md Pratik, Yuhao Li, Hang Yuen Ho, Shanchao Ouyang, Xinhui Lu, Hin-Lap Yip, Philip C. Y. Chow, Jean-Luc Brédas, Veaceslav Coropceanu, Shu Kong So, and Sai-Wing Tsang

Subjects
Science
Abstract

Abstract Organic photovoltaic cells using Y6 non-fullerene acceptors have recently achieved high efficiency, and it was suggested to be attributed to the charge-transfer (CT) nature of the excitations in Y6 aggregates. Here, by combining electroabsorption spectroscopy measurements and electronic-structure calculations, we find that the charge-transfer character already exists in isolated Y6 molecules but is strongly increased when there is molecular aggregation. Surprisingly, it is found that the large enhanced charge transfer in clustered Y6 molecules is not due to an increase in excited-state dipole moment, Δμ, as observed in other organic systems, but due to a reduced polarizability change, Δp. It is proposed that such a strong charge-transfer character is promoted by the stabilization of the charge-transfer energy upon aggregation, as deduced from density functional theory and four-state model calculations. This work provides insight into the correlation between molecular electronic properties and charge-transfer characteristics in organic electronic materials.

Published
2024
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2. Architecturally simple organic photodiodes with highly competitive figures of merit via a facile self-assembly strategy

Author

Hrisheekesh Thachoth Chandran, Hua Tang, Taili Liu, Sudhi Mahadevan, Kuan Liu, Zhen Lu, Jiaming Huang, Zhiwei Ren, Fuyou Liao, Yang Chai, Patrick WK Fong, Sai-Wing Tsang, Shirong Lu, and Gang Li

Subjects
Mechanics of Materials, Process Chemistry and Technology, General Materials Science, Electrical and Electronic Engineering
Abstract

By employing a self-assembled hole-blocking-layer (HBL), an elegant and broadly applicable architectural design framework is demonstrated to minimize the “performance-stability-cost” gap of the organic photodiodes.

Published
2023

4. Architecturally simple organic photodiodes with highly competitive figures of merit

Author

Hrisheekesh, Thachoth Chandran, Hua, Tang, Taili, Liu, Sudhi, Mahadevan, Kuan, Liu, Zhen, Lu, Jiaming, Huang, Zhiwei, Ren, Fuyou, Liao, Yang, Chai, Patrick Wk, Fong, Sai-Wing, Tsang, Shirong, Lu, and Gang, Li

Abstract

Photodetectors (PDs) based on organic materials exhibit potential advantages such as low-temperature processing, and superior mechanical properties and form factors. They have seen rapid strides toward achieving performance metrics comparable to inorganic counterparts. Here, a simplified device architecture is employed to realize stable and high-performance organic PDs (OPDs) while further easing the device fabrication process. In contrast to the sequential deposition of the hole blocking layer (HBL) and active layer (conventional 'two-step' processing), the proposed strategy forms a self-assembled HBL and active layer in a 'single-step' process. A high-performance UV-Vis-NIR OPD based on the PM6:BTP-eC9 system is demonstrated using this cost-effective processing strategy. The green solvent processed proof-of-concept device exhibits remarkable responsivity of ∼0.5 A W

Published
2022

5. Direct Observation of the Charge Transfer States from a Non-Fullerene Organic Solar Cell with a Small Driving Force

Author

Xiaojuan Sun, Qi Liu, Sudhi Mahadevan, Mingxuan Guo, Maojie Zhang, Peng Wan, Xingtong Chen, Sai-Wing Tsang, Jinjing Qiu, Song Chen, and Yongfang Li

Subjects
Dipole, Materials science, Fullerene, Organic solar cell, Chemical physics, General Materials Science, Charge (physics), Physical and Theoretical Chemistry, Absorption (electromagnetic radiation), Signal, Recombination, Polymer solar cell
Abstract

For organic solar cells (OSCs), the charge generation mechanism and the recombination loss are heavily linked with charge transfer states (CTS). Measuring the energy of CTS (ECT) by the most widely used technique, however, has become challenging for the non-fullerene-based OSCs with a small driving force, resulting in difficulty in the understanding of OSC physics. Herein, we present a study of the PM6:Y6 bulk heterojunction. It is demonstrated that electro-absorption can not only reveal the dipolar nature of Y6 but also resolve the morphology-dependent absorption signal of CTS in the sub-bandgap region. The device with the optimum blending weight ratio shows an ECT of 1.27 eV, which is confirmed by independent measurements. Because of the charge transfer characteristics of Y6, the charge generation at PM6:Y6 interfaces occurs efficiently under a small but non-negligible driving force of 0.14 eV, and the total recombination loss is as low as 0.43 eV.

Published
2021

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