Comprehensive approach to enhance perovskite solar cells efficiency and stability through charge transport and interlayer modifications
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Perovskite solar cells (PSCs) having numerous advantages for photovoltaic applications, such as high absorption coefficient, tunable bandgap, high crystallinity and long carrier diffusion length, attracted significant interest in the academic field in the recent decade. However, due to significant constraints in its fabrication, the perovskite solar cells field is still in its research and development stage. Generally, the commercial prospects of photovoltaic technology depend on cost, efficiency and stability. Perovskite solar cells are projected to be low-cost because they require small amounts of cheap materials and low production costs. However, even though power conversion efficiency has soared in the past decade, the stability of these cells still needs to improve to provide long-term viability. In this work, I employed passivation and compositional modification methods to improve charge transport and interfacial layers in the perovskite solar cells to enhance the efficiency and operation stability of perovskite solar cells. This work is divided into four chapters. In the first chapter, I discuss the fundamentals and recent challenges of the perovskite solar cell field; in the second and third chapters I introduce my research work, and in the last fourth chapter, I provide a summary and future work. In the second chapter, my research work is focused on the incorporation of a small organic molecule called EGTA (ethylene glycol-bis (β-aminoethyl ether)-N, N, N, N -tetraacetic acid) into the SnO2 colloidal solution. The formation of a complex with SnO2 allowed the EGTA-SnO2-based electron transport layer (ETL) devices to achieve an efficiency of 21.14% while maintaining good reproducibility under low-temperature manufacturing conditions. In addition, the EGTA-treated SnO2 solution demonstrates better surface coverage and improved electron mobility compared to the untreated SnO2-based ETL. At the same time, the number of defects at the interface between the ETL and perovskite layers was reduced, which resulted in the devices exhibiting negligible hysteresis. Unencapsulated EGTA-SnO2-based devices displayed improved stability under ambient settings, keeping more than 80% of their original efficiency over 500 h. In the third chapter, we used three distinct isomers of dicyanobenzene (DCB): ortho, meta, and para, as a passivation compound between the perovskite and the Spiro-OMeTAD hole transport layer. The meta-dicyano isomer significantly reduced the amount of unreacted lead iodide. PSCs that were passivated with 1,3-DCB increased PCE from 18.25% to 21.07%, reduced hysteresis and retains over 80% efficiency over 1000 h under ambient conditions. The performance improvement is related to the effective passivation of both shallow and deep charge traps. This work sheds some light on the impact of isomerism in the passivation of perovskite films and suggests a feasible approach to improving the performance of PSCs by using small organic compounds with two –CN functional groups. The final chapter summarizes the main findings of this work and suggests some future directions.
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Merlan Nurzhanov (2022). Comprehensive approach to enhance perovskite solar cells efficiency and stability through charge transport and interlayer modifications. UWSpace. http://hdl.handle.net/10012/18829