Advances in Engineering Advances in Engineering features breaking research judged by Advances in Engineering advisory team to be of key importance in the Engineering field. Papers are selected from over 10,000 published each week from most peer reviewed journals.
Significance
Solution-processed colloidal quantum dot light-emitting diodes (QLEDs) represent a significant advancement in the field of optoelectronics because of their high luminescence quantum yields, tunable emission spectra, and compatibility with flexible substrates. QLEDs offer promising applications in display technologies, lighting, and photonic devices. Despite the significant progress in the development of novel quantum dots (QDs) and optimization of device architectures, the widespread adoption of QLEDs still faces substantial hurdles, primarily due to the challenges associated with device fabrication and the imbalance in carrier injection. At the core of these challenges is the significant energy-level mismatch between commonly used QDs and traditional hole transport materials (HTMs), which is notably larger than the mismatch between QDs and commercial electron transport materials. This mismatch leads to an imbalance of charge carriers within the light-emitting layer (EML), adversely impacting the efficiency of QLED devices. Addressing this issue requires the design and development of novel HTMs with suitable electronic properties, a task complicated by the vast expanse of possible organic chemistry structures and the prohibitive costs associated with trial-and-error experimentation.
In a new study published in Chemistry of Materials, Dr. Hadi Abroshan, and team from Schrödinger, Inc., addressed the significant challenges facing the efficiency and widespread adoption of colloidal QLEDs. Specifically, they targeted the energy-level mismatch between the QDs used in these devices and the traditional HTMs, which leads to an imbalance of charge carriers within the EML, thereby reducing device efficiency. The researchers employed a novel strategy combining active learning (AL) and high-throughput density functional theory (DFT) calculations to efficiently navigate the vast search space of potential HTM materials. This approach was aimed at identifying promising HTM candidates with suitable electronic properties necessary for improving QLED performance, without the need for exhaustive and costly trial-and-error experimentation. The team built a comprehensive library of nearly 9,000 molecular structures, focusing on core molecular frameworks and functional groups prevalent in known HTMs. This library served as the foundation for their screening process. The AL framework was implemented to systematically sift through the materials library, prioritizing candidates based on multiple optoelectronic properties while minimizing the computational burden of DFT calculations. This iterative process allowed the team to refine their search and focus on the most promising materials. They conducted high-throughput DFT calculations to evaluate the electronic properties of selected HTM candidates. These calculations provided insights into the materials’ hole reorganization energies and highest occupied molecular orbital (HOMO) levels, crucial factors for efficient hole transport and injection in QLEDs. They identified top candidates through the AL-DFT workflow and underwent further assessment via molecular dynamics simulations and machine learning models. This subsequent analysis sought to evaluate hole-transporting rates and glass-transition temperatures, indicating the materials’ suitability for use in QLEDs.
The Schrödinger team successfully identified a subset of promising HTM candidates from the initial library of thousands of materials. These candidates exhibited optimal electronic properties, such as low hole reorganization energies and suitable HOMO levels, signaling their potential to enhance QLED efficiency by improving hole transport and injection. Moreover, the study demonstrated the power of combining computational methods like AL, DFT, and molecular dynamics simulations to accelerate the materials discovery process. This approach not only saves significant time and resources, but it also offers a more targeted pathway to identifying materials with the desired properties for specific applications.
In conclusion, the innovative approach presented by Dr. Abroshan and colleagues offers a promising pathway for overcoming the challenges associated with the development of efficient HTMs for QLEDs. Their research provided a robust framework for the rapid and efficient discovery of novel materials for optoelectronic applications. The authors’ findings pave the way for the next generation of optoelectronic devices with improved efficiency and broader applicability by addressing the critical issue of charge carrier imbalance in QLEDs.
Reference
Hadi Abroshan*, H. Shaun Kwak, Anand Chandrasekaran, Alex K. Chew, Alexandr Fonari, and Mathew D. Halls. High-Throughput Screening of Hole Transport Materials for Quantum Dot Light-Emitting Diodes. Chem. Mater. 2023, 35, 13, 5059–5070
