Interface engineering of nanocarbon-based hole-transporter-free perovskite solar cells

Organic/inorganic perovskite (CH3NH3PbI3, CH3NH3PbIxCl3-x) solar cells have emerged as a highly promising alternative renewable energy source because of their high efficiency and low-cost solution processable manufacturing processes. However, current perovskite solar cells typically require an expensive and air sensitive hole transporter material (HTM, e.g., spiro-MeOTAD) and a noble metal electrode (Au or Ag) deposited by complicated vacuum technology. These drawbacks, if not adequately addressed, will hinder the industrial development and market potential of perovskite solar cells. Therefore, it is highly desirable to study and develop alternative materials and processes that show high performance but are inexpensive, earth-abundant, stable, environmentally friendly, easily processable and energy non-intensive. My thesis is focused on the understanding and the development of nanocarbon-based HTM-free perovskite solar cells. The thesis is divided into 7 chapters. Chapter 1 surveys the current literature and outlines the motivation and objectives of my thesis. Chapter 2 introduces experimental techniques used in my experiments. Major findings of the study are presented and discussed from Chapters 3 to 6, with conclusions and outlooks summarized in Chapter 7. In chapter 3, I report a new modality of perovskite solar cells that do away with the use of conventional HTMs by directly clamping a selective hole extraction electrode made of candle soot and a deliberately engineered perovskite photoanode. Three generations of clamping solar cells were evolved from direct clamping to rolling-transfer clamping and to chemically promote clamping accelerated by the mechanistic understanding of inner workings. Up to this stage, the third generation clamping solar cells have already achieved a remarkable efficiency of 11.02% and good long term stability. The key soot/perovskite interface, which