Date

2023-2-24

Author

Bağ Çelik, Esra

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Perovskite solar cells (PSCs) have been widely studied for their potential to revolutionize the solar energy industry. Unfortunately, the commercialization of PSCs remains challenging due to the limitation of high-performance, low-cost, and environmentally stable organic hole-transport materials (HTMs). For this reason, the development of a new generation HTMs is strongly anticipated. Hole transport material (HTM) is one of the critical components in perovskite solar cells, which is responsible for transporting positive charges (holes) from the perovskite light- absorbing layer to the electrode. Traditional HTMs used in perovskite solar cells often contain dopants that can cause instability issues and lower the efficiency of the solar cells. The main emphasis of this hole-transport layer (HTL) research is on developing both hole-transport materials and dopants to develop HTL that can provide improved stability and excellent hole-transport properties to enhance the overall performance of perovskite solar cells. The research in this thesis aims to provide novel and cost-effective organic HTMs, p- type dopants for HTM, and ammonium salts for perovskite passivation towards the realization of high-performance PSCs. Overall, the high potential of novel organic dopant-free HTMs, p-type dopants with enhanced stability and passivating salts for significantly improving the efficiency and stability of perovskite solar cells makes them a promising avenue of research towards paving the day for commercialization of PSCs. In this thesis work, in chapter 3, a series of DPP-based polymers were investigated as HTMs in perovskite solar cells. For these polymers, the influence of aromatic groups, conjugated parts and alkyl chains on the performance of solar cells was systematically investigated. After optimization studies, the cell fabricated with HTM 4B has an efficiency of 16% and is placed well among the dopant-free polymer HTMs in the literature. In chapter 4, a TPA-based small molecule is introduced as a low-cost, dopant- free HTM for conventional n-i-p type PSCs, and the effect on the performance and cell stability is examined. PSCs with PT-TPA HTM exhibit a champion PCE of 17% and a substantively improved operational stability for unencapsulated cells tested at both controlled and ambient conditions. With the optimized HTL, PT-TPA-based cells saved its 96% of efficiency for 70 days under ambient conditions. In Chapter 5, through the utilization of a novel dopant, CFF, cells with comparable efficiencies to conventional doped HTMs, however highly stable as the cell with undoped HTMs, were developed successfully. While the maximum PCE was recorded in cells doped with CFF at 17.77%, CFF demonstrated excellent doping performance for HTMs, retaining 87% of its efficiency after 90 days of measurements. In chapter 6, three novel PMAI salts were introduced, which resulted in an increase in efficiency and enhancement of stability as a passivating layer on perovskite. A PCE value as high as 23.15% with extreme stability (97.8% retained cell efficiency retained after 1250 hours) was achieved with one of these salts, TPMAI.

Subject Keywords

Perovskite solar cell, hole transport material, polymer, dopant, passivation

URI

https://hdl.handle.net/11511/102768

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Graduate School of Natural and Applied Sciences, Thesis