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Increasing energy demand urge the development of advanced technologies to harvest clean energy, especially solar energy, to sustainably power the society. During my doctoral and postdoctoral studies, I developed hybrid heterojunction systems for efficient solar energy conversion and chemical fuel generation. In the future, I would contribute a research program of advanced materials for energy and optoelectronic devices.

Research Experience

Advisor: Jennifer Cha (University of Colorado Boulder)

My doctoral training mainly focused on complex nanomaterial assembly with biomolecules for renewable energy conversion. Artificial Z-scheme photosynthesis coordinates two types of material structures to spatially separate the photo-generated electrons and holes, and the key factor of this hybrid system is charge transfer process between the two photocatalytic materials. I developed an innovative DNA-nanotechnology strategy to accomplish precisely-controlled spatial organization of heterogeneous semiconducting nanocrystals, which allowed comprehensive investigation of the inter-particle charge transfer. Efficient full water splitting and CO2 reduction reactions were resulted from these ordered systems. This effort provided a platform which enables insights into the charge transfer kinetics in heterogeneous photosynthetic system. Additionally, I investigated the metallization of DNA bridges and other synthetic polymers to further improve inter-particle charge transfer.

Advisor: Letian Dou and Jianguo Mei (Purdue University)

While as a Lillian Gilbreth Postdoctoral Fellow in Purdue University, I led the project of functionalized interfaces between perovskite and hole transporting layer for efficient charge transfer in solid state solar cells. The high trap density at the surface of perovskite thin films leads to interfacial non-radiative recombination, which requires effective passivation to achieve efficient and stable solar cells. I investigated the employment of conjugated ligands as passivation layer to stabilize device interfaces while at the same time facilitating charge transfer. The success of this project immediately transferred the fundamental knowledge we obtained, about organic semiconductor-incorporated 2D perovskites, to applications in devices. These efforts resulted in an DOE Solar Energy Technologies Office (SETO) award offered to the group. Currently, I’m leading the SETO project team, making steady progress toward efficient and stable perovskite solar cells. Meanwhile, I’m continuing advancing the understanding of interfacial charge transfer in perovskite solar cells through manipulating the organic hole transporting material and new interface layer design. Through tuning the configurations of the conjugated ligands, the energy landscape of perovskite surface can be flattened to lower the charge transport energy barrier. Furthermore, the growth of surface 2D perovskite can be further tailored by rational design of ligands, allows improved interfacing at 2D and 3D perovskite heterojunction. Beside the ligand design, I’m also investigating the degradation mechanism of perovskite solar cells with various electric and chemical characterization methods.

Research Interests

My future research will focus on programming the surface of colloidal nanocrystals and assembling them into efficient devices to address challenges in energy utilization. I believe a comprehensive understanding of nanocrystal surface chemistry will reconstitute the current scope of nanocrystal properties and connect the isolated nanocrystals into a network for efficient devices. I will pursue this goal by developing methods to manipulate surface electronic and chemical structures through effectively interfacing organic and inorganic semiconducting materials. The initial material system of interests will be halide perovskite due to its unique hybrid compositions and properties. These research interests will enable complex superlattice assembly and allow investigation of exciting new optical and electronic properties. The understanding of nanocrystal surface properties can be further adopted to the investigation of bulk material and interfacing bulk and nano material. Thus, in parallel, my lab will also employ the surface chemistry, assembly strategies, and device engineering to fabricate efficient and stable devices, and develop method for large scale fabrication. The ultimate motivation of my lab will be efficiently utilizing energy in optoelectronic devices by manipulating semiconducting materials.

Teaching Interests

I developed interests in teaching and educating the young generations. I believe that a good teacher can stimulate the students’ interests and curiosities, and teach them the method of logical thinking to seek answers. I was able to acquire experience in interacting with students and practice my teaching concepts through a number of teaching opportunities (Polymer Engineering, Nanomaterials, and Principles of Molecular Engineering). I also put this spirit into practice while mentoring several mentees, including both undergraduate and graduate students. My research background in chemical engineering, material science, and electronic materials and devices has given me experience in most chemical engineering courses.

Selected Awards and Publications

Lillian Gilbreth Postdoctoral Fellowship (2019-2021): Annual stipend of $60,000.00 and benefits

Liang, A.*; Ma, K.*; Gao, Y.; Dou, L. Tailoring Anchoring Groups in Low-Dimensional Organic Semiconductor-Incorporated Perovskites. Small Structure. 2022, 3, 2100173.

Ma, K.; Gao, Y.; Zhao, Q.; Finkenauer, B.P.; Atapattu, H.R.; Wang, K.; Coffey, A.H.; Zhu, C.; Graham, K.R.; Huang, L.; Mei, J.; Dou, L. Multi-Functional Conjugated Ligand Engineering for Stable and Efficient Perovskite Solar cells, Adv. Mater. 2021, 2100791.

Ma, K.; Hsu, S.-N.; Gao, Y.; Wei, Z.; Jin, L.; Finkenauer, B.P.; Huang, L.; Boudouris, B.W.; Mei, J.; Dou, L. Lead-Free Perovskite Quantum Well Solar Cells with High Stability, Small Science 2021, 200024.

Ma, K.; Yehezkeli, O.; He, L.; Cha, J. N. DNA for Assembly and Charge Transport for Photocatalytic Reduction of CO2. Adv. Sustainable Syst. 2018,1700156.

Ma, K.; Harris, A. W.; Cha, J.N. DNA-assembled photoactive systems. Curr. Opin. Colloid Interface Sci. 2018, 38, 18-29.

Ma, K.; Yehezkeli, O.; Park, E.; Cha, J. N. Enzyme Coupled Photoelectrochemical Cells for Increased Methanol Production from CO2. ACS Catalysis. 2016, 6, 6982-6986.

Ma, K.; Yehezkeli, O.; Domaille, D. W.; Funke, H. H.; Cha, J. N. Enhanced Hydrogen Production from DNA-Assembled Z-Scheme TiO2-CdS Photocatalyst Systems. Angew. Chemie - Int. Ed. 2015, 54, 11490-11494.

Ma, K.*; Sun, J.*; Varadharrajan, D.; Lee, Y.H.; Atapattu, H.R.; Aidan, A.H.; Graham, K.R.; Dou, L. Molecular Engineering Tailored Interface for Efficient and Stable Perovskite Solar Cells with Conducting Polymer. In preparation