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820 results on '"Hao, Xiaojing"'

1. Influence of Organic Spacer Cation on Dark Excitons in 2D Perovskites

Author

Bailey, Christopher G., Gillan, Lara V., Lee, Minwoo, Sloane, Nicholas, Liu, Xu, Soufiani, Arman Mahboubi, Hao, Xiaojing, and McCamey, Dane R.

Subjects
Condensed Matter - Materials Science, Physics - Applied Physics
Abstract

The organic spacer cation plays a crucial role in determining the exciton fine structure in two-dimensional (2D) perovskites. Here, we use low-temperature magneto-optical spectroscopy to gain insight into the influence of the organic spacer on dark excitons in Ruddlesden-Popper (RP) perovskites. We show that by using modest magnetic field strengths (<1.5 T), the spin-forbidden dark exciton state can be identified and its emission properties significantly modulated through the application of in-plane magnetic fields, up to temperatures of 15 K. At low temperatures, an increase in collected photoluminescence efficiency of >30% is demonstrated, signifying the critical role of the dark exciton state for light-emitting applications of 2D perovskites. The exciton fine structure and the degree of magnetic-field-induced mixing are impacted by the choice of organic spacer cation, with 4-methoxyphenethylammonium (MeO-PEA) showing the largest effect due to larger bright-dark exciton splitting. Our results suggest that dark excitons preferentially form biexcitons depending on the choice of spacer. We distinguish between interior (bulk) and surface dark-exciton emission, showing that bright-dark exciton splitting differs between the interior and surface. Our results emphasize the significance of the organic spacer cation in controlling the exciton fine structure in 2D perovskites and have important implications for the development of optoelectronic technology based on 2D perovskites.

Published
2023
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32. Methylammonium‐Free Ink for Low‐Temperature Crystallization of α‐FAPbI3 Perovskite.

Author

Hou, Tian, Zhang, Meng, Sun, Xiaoran, Wang, Yihao, Chen, Kaipeng, Fu, Zhipeng, He, Mingrui, Liu, Xu, Liu, Ziheng, Huang, Yuelong, Green, Martin A., and Hao, Xiaojing

Subjects
HUMIDITY control, SOLAR cells, PEROVSKITE, PHOTOVOLTAIC power generation, CRYSTALLIZATION
Abstract

Formamidinium lead triiodide (FAPbI3) perovskite without methylammonium and/or Cs cations is considered the most promising candidate for perovskite photovoltaics. However, the crystallization of photoactive α‐FAPbI3 requires high‐temperature annealing (≥150 °C) and a controlled humidity environment when methylammonium‐containing additives are absent. A methylammonium‐free ink is reported that enables low‐temperature (≤80 °C) crystallization of photoactive α‐FAPbI3 films, while also demonstrating compatibility with blade‐coating large‐area films in ambient air. The synergistical effects of methylphenyl sulfoxide and PbCl2 facilitate the formation of an intermediate phase of nanoscale‐disordered δ‐FAPbI3, which dramatically reduces the crystallization temperature of α‐FAPbI3 down to 80 °C and even below. The 80 °C crystalized α‐FAPbI3 exhibits reduced strain and improved uniformity compared to high‐temperature annealed counterparts. The synthesized ink and the corresponding intermediate precursor film are also found remarkably stable, allowing open‐air processing without the need for humidity control. Highly efficient n–i–p structured α‐FAPbI3 minimodules can be fabricated under an ambient environment RH 50% with the ink at 80 °C, achieving a power conversion efficiency of up to 22.4%. The discovery of the low‐temperature FAPbI3 ink paves a new avenue for printing perovskite solar cells and associated optoelectronic applications, accelerating the commercialization progress of perovskite materials. [ABSTRACT FROM AUTHOR]

Published
2024
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42. Cd-Free Pure Sulfide Kesterite Cu2ZnSnS4 Solar Cell with Over 800 mV Open-Circuit Voltage Enabled by Phase Evolution Intervention

Author

Wang, Ao, Huang, Jialiang, Cong, Jialin, Yuan, Xiaojie, He, Mingrui, Li, Jianjun, Yan, Chang, Cui, Xin, Song, Ning, Zhou, Shujie, Green, Martin A., Sun, Kaiwen, Hao, Xiaojing, Wang, Ao, Huang, Jialiang, Cong, Jialin, Yuan, Xiaojie, He, Mingrui, Li, Jianjun, Yan, Chang, Cui, Xin, Song, Ning, Zhou, Shujie, Green, Martin A., Sun, Kaiwen, and Hao, Xiaojing

Abstract

The Cd-free Cu2ZnSnS4 (CZTS) solar cell is an ideal candidate for producing low-cost clean energy through green materials owing to its inherent environmental friendliness and earth abundance. Nevertheless, sulfide CZTS has long suffered from severe open-circuit voltage (V-OC) deficits, limiting the full exploitation of performance potential and further progress. Here, an effective strategy is proposed to alleviate the nonradiative V-OC loss by manipulating the phase evolution during the critical kesterite phase formation stage. With a Ge cap layer on the precursor, premature CZTS grain formation is suppressed at low temperatures, leading to fewer nucleation centers at the initial crystallization stage. Consequently, the CZTS grain formation and crystallization are deferred to high temperatures, resulting in enhanced grain interior quality and less unfavorable grain boundaries in the final film. As a result, a champion efficiency of 10.7% for Cd-free CZTS solar cells with remarkably high V-OC beyond 800 mV (63.2% Schockley-Queisser limit) is realized, indicating that nonradiative recombination is effectively inhibited. This strategy may advance other compound semiconductors seeking high-quality crystallization.

Published
2024

45. Solar cell efficiency tables (Version 64).

Author

Green, Martin A., Dunlop, Ewan D., Yoshita, Masahiro, Kopidakis, Nikos, Bothe, Karsten, Siefer, Gerald, Hinken, David, Rauer, Michael, Hohl‐Ebinger, Jochen, and Hao, Xiaojing

Subjects
SOLAR cell efficiency, ENERGY consumption
Abstract

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since January 2024 are reviewed. [ABSTRACT FROM AUTHOR]

Published
2024
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46. Refining Photothermal Deflection Spectroscopy: Incorporating Reflectance for Enhanced Accuracy in Light‐Absorption Measurements.

Author

Asami, Meita, Kampwerth, Henner, Pollard, Michael, Hao, Xiaojing, Komaba, Shintaro, Ikari, Tetsuo, Fukuyama, Atsuhiko, Watanabe, Kentaroh, Nakano, Yoshiaki, and Sugiyama, Masakazu

Subjects
PHOTOTHERMAL spectroscopy, REFLECTANCE spectroscopy, LIGHT absorption, OPTOELECTRONIC devices, ABSOLUTE value, PROBLEM solving
Abstract

A method for measuring light absorption using photothermal deflection spectroscopy (PDS) is investigated. Typical reflectance and transmittance (R & T) absorption measurements have low spectral resolution (SR) with standard setups. It is believed that absorption measurements using PDS solve this problem because of its high sensitivity, even at a high SR. However, accurate absorption measurements have not been obtained using conventional PDS. The reflectance of the sample must be considered in the absorptance calculations. Various absorption measurement methods are compared and a novel calculation method for accurate PDS absorption measurements is proposed. A sample with quantum structures is fabricated and PDS measurements are performed. Exciton absorption peaks are also observed. The high SR of PDS is demonstrated and the measured exciton absorption peaks are confirmed using piezoelectric photothermal measurements. Furthermore, it is confirmed that the absolute values of absorptance derived from the R & T and PDS measurements agree well. The new PDS absorption measurement technique enables to obtain accurate absorption characteristics, which are indispensable for designing and optimizing optoelectronic devices. [ABSTRACT FROM AUTHOR]

Published
2024
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47. A collaborative framework for unifying typical multidimensional solar cell simulations – Part I. Ten common simulation steps and representing variables.

Author

Ma, Fa‐Jun, Wang, Shaozhou, Yi, Chuqi, Zhou, Lang, Hameiri, Ziv, Bremner, Stephen, Hao, Xiaojing, and Hoex, Bram

Subjects
SOLAR cells, TEXT files, ARTIFICIAL intelligence, COMPUTER programming, COMPUTER simulation, PHOTOVOLTAIC power systems
Abstract

Multidimensional simulations for diverse solar cells often encounter distinctive configurations, even when employing the same simulation software. The complexity and inefficiency of this process are further exacerbated when employing different simulators. From our extensive decade‐long experience in numerical simulations of diverse solar cells, we have identified ten common simulation steps intrinsic to typical electrical and optical simulations. Subsequently, we propose ten sets of variables that encompass all the relevant details required for these steps. To address the challenge of varying information requirements for each variable across different simulations, we assign a list, a versatile data type, to each variable. This approach, by design, enables concise, coherent, and flexible input, accommodating the unique demands of each simulation. However, to ensure unambiguous simulations, precise specifications for these variables are essential. Computer code has been successfully implemented to ensure adherence to specifications and expedite variable synchronization with Sentaurus, the de facto standard for device simulation. Within this framework, users are only tasked with editing variables in a plain text file, obviating the need for in‐depth knowledge of Sentaurus. This streamlines the prerequisites for engaging in numerical simulation significantly. Through thoughtful design considerations, we preserve the simulation capacity while simultaneously enhancing productivity considerably. This open‐source framework welcomes global collaboration within the photovoltaic community and has the potential to generate an extensive dataset for cost‐effective artificial intelligence training. [ABSTRACT FROM AUTHOR]

Published
2024
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