Muhammad Awais

Topic

Stable and Efficient Perovskite Solar Cells Fabricated in Ambient Air

Department of Electrical and Computer Engineering

Date & location

• Thursday, August 14, 2025

• 9:00 A.M.

• Elliott Building

• Room 305

Reviewers

Supervisory Committee

• Dr. Makhsud Saidaminov, Department of Electrical and Computer Engineering, University of Victoria (Supervisor)

• Dr. Tom Tiedje, Department of Electrical and Computer Engineering, UVic (Member)

• Dr. Alexandre Brolo, Department of Chemistry, UVic (Outside Member) 

External Examiner

• Dr. Ahmad Kirmani, Department of Chemistry and Materials Science, Rochester Institute of Technology 

Chair of Oral Examination

• Dr. Roberta Hamme, School of Earth and Ocean Sciences, UVic

   

Abstract

Search for efficient energy materials has been at the forefront of mitigating climate change and meeting ever-growing energy demand. Solar cells have proven to facilitate both challenges, and significant efforts were dedicated in improving the current state-of-art technology, i.e., silicon solar cells, but also to look for more efficient and inexpensive materials. Among them, perovskite solar cells (PSCs) have shown promising results within a decade and are now at the edge of commercialization.  

This thesis focuses on addressing the key challenges in fabricating stable and efficient PSCs under ambient conditions, a crucial step toward their scalable production and industrial manufacturing viability. While PSCs exhibit outstanding optoelectronic properties, their performance and stability are compromised by both extrinsic environmental factors (moisture, heat, oxygen) and intrinsic material/interface instabilities. This thesis adopts a comprehensive approach by developing robust ambient-air fabrication protocols to overcome environmental sensitivity, and surface passivation of electron transport layer and perovskite towards scalable fabrication of efficient perovskite solar cells. By systematically addressing these extrinsic and intrinsic stability challenges through material engineering, interface optimization, and reliable encapsulation methods, this bridges the gap between laboratory-scale fabrication and industrially relevant manufacturing requirements for PSCs.  

Chapter 1 provides an overview of the global energy landscape, highlighting the environmental impacts of non-renewable resources and the pivotal role of solar energy in addressing these challenges. Focusing on photovoltaic technologies, it introduces PSCs as a promising solution, detailing their crystal structure and optoelectronic properties. The chapter systematically reviews PSC fabrication, covering perovskite composition selection, role of charge transport layers, and metal electrode. It concludes with performance characterization metrics and device improvement strategies, providing a foundation for advancing PSC technology in subsequent research. 

In Chapter 2, the thesis addresses the challenge of extrinsic factors by developing optimized methods and protocols for ambient-air fabrication. A key component of this work involves a comparative study of two widely reported perovskite compositions: CsMAFA and MAFA (Cs: cesium; MA: methylammonium, CH3NH3 +; FA: formamidinium, HC(NH2)2 +). This chapter reveals that the CsMAFA perovskite exhibits instability in ambient air, attributed to the hygroscopic nature of cesium. To evaluate long-term operational stability, an accelerated aging protocol to test encapsulated devices under extreme conditions is also developed. This chapter achieves a milestone of 20% efficiency for PSCs made in ambient conditions. 

Chapter 3 focuses on the grain boundary degradation in perovskite films, which is one of the major sources of degradation. A selective passivation strategy using biphenyl containing molecules that specifically interact with PbI2-rich interfaces at grain bounderies while remaining inert toward the perovskite is developed. This targeted approach results in significant improvements in optoelectronic properties, extending the radiative recombination lifetime from 1 µs to 2.7 µs. When implemented in ambient-air fabricated devices, this technique demonstrates excellent reproducibility, with champion device achieving an efficiency of 21% and consistently high open-circuit voltages of ~1.1 V. 

Chapter 4 introduces chemical bath deposition method for fabricating SnO2 electron transport layers in fully scalable, ambient-air-processed perovskite solar cells. The optimized deposition approach enables uniform, high-quality SnO2 films that enhance charge extraction and minimize interfacial recombination. PSCs fabricated entirely using scalable methods under ambient conditions achieve an efficiency of 24.5%. The devices demonstrated excellent photovoltaic parameters, including an open-circuit voltage of ~1.14, validating the effectiveness of this scalable SnO2 deposition technique for high-performance all-scalable PSC fabrication.

Finally, this thesis concludes with the conclusion and outlook in Chapter 5.