Design and synthesis of polymeric semiconductors for perovskite applications
Perovskite solar cells (PSCs) have demonstrated remarkable efficiency growth in their brief history, and are considered to be of exceptional potential for commercialization due to their excellent absorption properties, varied deposition methods, and compatibility with other solar technologies. Furthermore, perovskites are demonstrating high potential for other applications, such as perovskite light emitting diodes (Pero-LEDs), lasers, and radiation detectors. Most perovskite based devices use hole transporting materials (HTMs) to assist in charge separation and current generation. The three main categories of HTM are inorganic materials, small organic molecules, and polymeric materials. Organic materials typically provide the highest efficiencies for these devices, but have several drawbacks including low economic viability, lack of flexibility for use with the various perovskite absorber layers (PALs), and difficulty of application in the multiple device architectures that exist for these devices. This dissertation primarily describes the design and synthesis of new polymeric materials to improve the processibility and interfacial interactions of HTM and PAL, leading to high efficiency, high stability, and low cost PSCs. Our current research into HTMs takes a four-pronged approach; We found that utilizing the Buchwald-Hartwig amination protocol using primary aryl amines and aryl dihalides afforded highly reproducible, high yielding family of polymers, which could be purified by a simple sequence of precipitations. Appropriate selection of pendant functional groups, such as electron donating methoxy, or electron withdrawing fluorine, allowed for highest occupied molecular orbital (HOMO) tuning, as did the utilization of electron rich carbazole versus the neutral fluorene in the polymer backbone. Control of the glass transition temperature (Tg), a characteristic vital to extended lifetime at elevated temperature, was demonstrated by manipulation of the alkyl side chains in the polymer, which allowed for a balance of solubility and improved Tg. Finally, side chain engineering of the polymers, incorporating more hydrophilic functional groups, was explored to improve the processibility of the PAL on top of the polymer HTMs. This allowed for the manufacture of devices that did not require an interfacial layer or UV/Ozone treatment to form a consistent perovskite film, removing a variable in the device, as well as reducing processing time and cost
Buchwald-Hartwig, perovskite, polymer, semiconductor, solar cell, synthesis
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Colorado School of Mines. Arthur Lakes Library