Abstract Title: Charge transport in hybrid organic-inorganic halide perovskites
Hybrid organic-inorganic trihalide perovskites have emerged as one of the most promising contenders for large scale photovoltaic energy generation. These materials exhibit a remarkable set of properties, coupled with low production cost, which led to an avalanche of research on this topic and a commendable growth. Unlike most mature technologies, however, the innovation witnessed in the field outstripped our understanding of basic these materials properties. In addition, the hybrid perovskites contain lead, which represent an environmental hazard, precluding their incorporation in future applications. This project is a collaborative effort between a research group at Wake Forest University with expertise in device fabrication and electrical characterization and a group at University of Utah with knowledge on materials growth, optical and magnetic field effect measurements. The research will focus on the investigation of the electronic processes that limit the operation and stability of hybrid perovskite-based devices; designing and implementing device structures that promote improved performance; and developing lead-free hybrid perovskites. Driven by the anticipated high impact of hybrid perovskite electronics on the US economy and society, this interdisciplinary research program will integrate education by implementing a strong teaching and mentoring component that complements all stages of the research efforts.
The research will focus on novel hybrid organic-inorganic perovskites (HTP) single crystals and thin-film growth, structural, optical and electrical characterization, device design, fabrication, and characterization with the following objectives: (i) develop Pb-free hybrid perovskites; (ii) understand the mechanism of charge transport in hybrid perovskite materials; (iii) elucidate the coexistence between the electronic and ionic transport and their contribution to HTP device hysteresis, performance, reliability and stability. The project is structured into three phases. The first phase focuses on the study of charge transport in HTPs using time of flight, space-charge-limited current and FET measurements at various temperatures. In the second phase we will focus on the analysis of bulk and surface defect states by performing Poole-Frenkel and density of states analysis. In the third phase the PIs will disentangle the ionic and electronic contributions to the conductivity in HTP devices using Seebeck effect in the dark and under illumination, and impedance spectroscopy. The PIs and their research groups will continue and expand their efforts dedicated to enhancing the growth of the new field of perovskite electronics by organizing conferences, participating in activities at local science museums, and offering research opportunities to students from local community colleges and high schools.
