Yip Group @ CityU HK
Hybrid and Organic Materials for Energy Applications
Main research topics
Organic Solar Cells
Owing to the advancement in new material design over the past few years, the power conversion efficiencies (PCE) of organic/polymer solar cells (OSCs) have now reached over 18%. However, in order the meet the commercialization requirement, further improvement in device stability and the exploration of niche applications of organic solar cells are urgently needed. In my group, we utilize an integrated strategy combining material design, interface engineering and optical management to tackle the efficiency and stability challenges of OSCs. We are particularly interested in using optical management as a powerful means to enhance the performance of OSCs by maximizing the light harvesting property of the devices. The capability to use optical model to precisely predict the light propagation property and charge generation rate within the devices allows us to design optimal device architectures with improved performance. A high throughput optical model developed in our group allows us to rapidly screen more than millions device structures in order to identify the very best device design for extremely high performance tandem and semitransparent OSCs (ST-OSCs). In addition, we also explore niche application of OSCs, highlighting how to engineer the optical property of ST-OSCs for smart greenhouse applications, as well as the design of multiple-function ST-OSC with both heat insulation and power generation properties.
For more information, you can watch the seminar entitled "Structure-Property Relationships in Organic Photovoltaics: From Molecular Design to Niche Applications" using this link.
Perovskite Solar Cells
Over the past few years, organic-inorganic hybrid perovskites have emerged as a new class of solution processable semiconductor for many optoelectronic applications, such as solar cells and light emitting devices (LEDs). Their electronic, electrical and optical properties can be controlled by tuning their compositions and crystal structures. Our research focuses on how to control the dimensions and nanostructures of perovskites by introducing small molecules and polymers with tailored functional groups that can strongly interact with the perovskite crystals. Using such strategy, we aim to develop very stable all-inorganic, MA-free and Sn-based low bandgap perovskite solar cells with much improved stability and efficiency. We also lean on the experience in interface engineering for organic solar cells and design desired new electron and hole transport conjugated materials with proper interfacial properties to improve the charge collection efficiency of p-i-n or n-i-p heterojunction perovskite solar cells.
Perovskite Light Emitting Devices
Light-emitting diodes (LEDs) are new-generation lighting devices that have been substituting the traditional filament lamps and fluorescent lamps. In recent years, perovskite materials show a bright prospect in the LED application based on their excellent optoelectronic properties and processing compatibilities. Combining the unique advantages of organic LEDs and inorganic LEDs, perovskite LEDs (PeLEDs) are color-tunable, color-pure, low-cost, flexible and compatible with large-scale and printing processes, showing a great potential to be the next-generation LEDs.
In the PeLED field, three main research directions in our group are 1) promoting device efficiency, 2) improving device stability and 3) understanding fundamental physics within PeLEDs. In the device-efficiency part, we mainly focus on white and blue PeLEDs based on perovskite and device designs. In the device-stability part, we mainly focus on studying the device degradation mechanism and develop new strategy to improve device stability. For fundamental physics study, we mainly focus on the optical management, carrier dynamics and photophysics in PeLEDs, to provide fundamental guidance for PeLED development. In addition, we welcome any possible collaboration to further promote the development of PeLEDs in interdisciplinary fields.
Our research group also focuses on designing and fabricating advanced multilayer and tandem optoelectronic devices based on solution-processed semiconductors like organic and perovskite materials. These materials provide benefits such as low-cost processing, mechanical flexibility, and large-area fabrication potential. Tandem devices, used in applications like solar cells and LEDs, can outperform single-junction devices by utilizing a broader spectrum and combining complementary material properties. This leads to increased efficiency and enhanced performance. To achieve this, we concentrate on several key research areas:
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Material Development: We synthesize novel organic and perovskite materials with improved optoelectronic properties to design multilayer structures with optimized energy bandgaps and tailored optical properties for efficient photon absorption and emission.
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Interface Engineering: We investigate interfacial strategies, including novel buffer layers, surface passivation techniques, and interface modifications, to minimize energy losses and enhance charge extraction in multilayer and tandem devices.
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Device Architecture Optimization: We explore advanced device architectures for applications like perovskite/organic tandem solar cells and multilayer solution-processed LEDs. Employing multi-physics simulations, encompassing optical, electrical, and thermal aspects, we optimize device configurations for improved performance.
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Scalable Fabrication Techniques: We develop scalable solution-processing techniques for large-area, uniform, and defect-free multilayer and tandem devices, integrating advanced printing and coating methods.
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Stability and Lifetime: We address long-term stability and operational lifetime by investigating degradation mechanisms, encapsulation strategies, and material stability under various environmental conditions.
By integrating material development, interface engineering, device optimization, scalable fabrication techniques, and stability studies, our research group aims to advance solution-processed optoelectronic devices, driving transformative innovations in the field.
Multilayer and Tandem Optoelectronic Devices
