Research

Current Research Projects

1. Solution-Processed Perovskites Hybrid Solar Cells: Perovskite hybrid solar cells (pero-HSCs) have attracted significant attention due to the excellent optical and electrical properties of perovskite materials and high power conversion efficiency of pero-HSCs. The objectives of this project are to develop novel organometal halide perovskite materials, fabricate both planar heterojunction (PHJ) and bulk heterojunction (BHJ) pero-HSCs. The project involves chemistry, device physics and device engineering. The project is both fundamental and applied as we try to understand how thin film morphology of organometal halide perovskite materials, device fabrication processes and interfacial engineering affect device performance of both PHJ and BHJ pero-HSCs. The goal is to approach high efficiency of pero-HSCs. Please read the references of Energy & Environ. Sci., 2015, 8(4), 1245, Adv. Energy Mater., DOI:10.1002/aenm.201402024, Organic Electronics, 2015, 21, 19-26 for more information.
2. Ultrasensitive Solution-Processed Broadband Polymer Photodetectors: Sensing from the ultraviolet (UV)-visible to the infrared is critical for a variety of industrial and scientific applications, including image sensing, communications, environmental monitoring, remote control, day- and night-time surveillance and chemical/biological sensing. Today, separate sensors are fabricated from inorganic materials for different sub-bands within the UV to near-infrared wavelength range. The objectives of this project are to fabricate uncooled ultrasensitive solution-processed broadband polymer photodetectors by novel semiconducting polymers and to investigate how interfacial layers to boost the phot-ocurrent, minimize the dark-current and suppress surface charge carrier recombination, consequently, enhance the detectivity of polymer photodetectors. For more information, please read following references: Science, 2009, 325, 1665, J. Phys. Chem. C., 2013, 117, 6537, and J. Mater. Chem. C. 2014, 2, 9592.
3. Organic Thermoelectric Devices: Thermoelectric devices directly convert heat into electricity without moving parts or working fluids, making them reliable and compact compared with conventional heat engines. Organic semiconductors offer numerous advantages over inorganic semiconductors for thermoelectric applications, such as low cost, large-area deposition, high toughness and elasticity, materials abundance and low weight. In this project, we will investigate the effect of dopants in organic semiconductors to enhance the electrical conductivity, hence, the thermoelectric power efficiency of organic thermoelectrics. In particular, we will study: (1) how to increase the electrical conductivity of organic semiconductors by doping ionic counter? (2) what is the ionization fraction over a wide range of dopant concentrations? (3) what is the correlation between the Seebeck coefficient and dopant concentration? (4) what is the correlation between power efficiency and the thin film morphology of doped polymers? Please see ACS Applied Materials & Interfaces, 2015, 7, 8984 for more information.
4. Toward High Performance Inverted Polymer Solar Cells: Polymer solar cells (PSCs) are of growing interest due to their low-cost and large-area manufacturing process. In the past years, power conversion efficiency (PCE) of the state of the art were over 10% has been observed from PSCs with a regular device structure, where, the indium tin oxide (ITO) acts as the anode and the air sensitive metals acts as cathode. PSCs with a conventional device structure are susceptible to have poor stability and incompatible to large-area roll-to-roll manufacturing. In this project, we will investigate PSCs with an inverted device structure where ITO acts as the cathode and air insensitive metal pastes acts as the anode. We will further correlate the PCEs of PSCs with the thin film morphology of bulk heterojunction composite and interfacial layers. Please read following references for more information: Energy & Environmental Science, 2012, 5, 8208, Adv. Eng. Mater., 2014, DOI: 10.1002/aenm.201400378, Nanoscale, 2014, 6, 14297-14304, ACS Applied Materials & Interfaces, 2015, 7(8), 4928.
5. Broadband Photodetectors with Perovskite Materials and Quantum Dots as the Light Sensors: The objectives of this project are to fabricate bulk heterojunction polymer PDs by novel semiconducting polymers and to investigate how interfacial layer to boost the photo-current, minimize the dark-current and suppress surface charge carrier recombination to enhance detectivity of polymer PDs. For more information, please read following references: Science, 2009, 325, 1665, J. Mater. Chem. C. 2015, 3, 6600.
6. Effect of Magnetic Nanoparticles and External Magnetic Field on Polymer Solar Cells: The price of energy to separate tightly bound electron-hole pair (or charge-transfer state) and extract freely movable charges from low-mobility materials represents fundamental losses for many low-cost photovoltaic devices. In bulk heterojunction (BHJ) polymer solar cells (PSCs), approximately 50% of the total efficiency lost among all energy loss pathways is resulted from the photogenerated charge carrier recombination within PSCs and low charge carrier mobility of disordered organic materials. In this project, PSCs incorporated with magnetic nanoparticles and external magnetic field will be investigated. The thin film morphology of BHJ composite, charge carrier recombination and collection efficiency will be studied. For more information, please read Scientific Reports, 2015, 5, 9265, ACS Appl. Mater. & Interfaces, 2014, 6, 13201, ACS Appl. Mater. & Interface, 2013, 5, 10325.
7. Self-Powered Electronics by Supercapacitors Integrated with Solar Cells: With the rapid development of the electronic technology, the portable and wearable personal devices and flexible electronics now become increasingly pervasive in our daily life. There is a growing demand for flexible, lightweight, high energy density and long lasting energy storage devices. In this project, we will fabricate a self-powered system by solar cells integrated with supercapacitors. The flexible all-solid-state graphene based supercapacitors will be firstly fabricated and characterized, and then integrated with high efficiency solar cells created in my lab. Lastly, the device performance including charge and discharge properties and stability of self-powered system will be evaluated. For more information, please read following reference: Advanced Functional Materials, 2015, 25, 2420-2427.