Organic-inorganic hybrid halide perovskites have rapidly become a focal point of the photovoltaic (PV) community as a promising next-generation PV technology. Various perovskite absorbers and device architectures have been examined. The certified efficiency of a single-junction perovskite solar cell (PSC) has reached over 22% after only several years of active research. Despite this remarkable progress associated with perovskites, there are still many fundamental questions to be addressed at both material and device levels. In this presentation, I will discuss our recent studies toward a better understanding and control of perovskite nucleation, grain growth, and microstructure evolution using solution processing. We find that a simple post-growth CH3NH3Br treatment to the perovskite CH3NH3PbI3 thin films can induce substantial grain coarsening via Ostwald ripening, leading to much improved film properties regardless of the initial film quality (e.g., pinholes and grain size). Thus, this new chemical approach enhances processing tolerance to the initial perovskite film quality and improves the reproducibility of device fabrication. Next, I will discuss our recent effort on scalable deposition of perovskite thin films toward future perovskite PV module fabrication. The rapid PSC efficiency improvements over the past several years have been achieved using the lab-scale spin coating technique. There is still a wide gap between spin coating and scalable deposition methods (e.g, blade coating, slot die, spray, inkjet printing, electrochemical deposition), making it challenging to reach its potential in mass production. The discrepancy between these techniques mainly lies in the different final perovskite film morphologies caused by vast distinctive casting/drying/crystallization/conversion mechanisms. The precursor ink chemistry of perovskite for scalable deposition is critical, but has been underexplored. We present a rational design of perovskite precursor film formation to achieve highly specular film using scalable deposition methods, leading to efficient perovskite PV modules with monolithically interconnected subcells. This finding makes a significant advance toward commercialization of the perovskite PV technology.

Perovskite photovoltaics: Materials, cells and modules

254th National Meeting (2017)

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