Researchers at Cornell University demonstrated a process to optimize the fabrication of perovskite solar cells, resulting in thin, reliable, efficient and low-cost solar cells. The study has been published in Nature Communications.
The research team comprising Lara Estroff, associate professor of materials science and engineering, and Uli Wiesner, the Spencer T. Olin Professor of materials science and engineering, showed how to improve the manufacturing conditions of thin film solar cells that offer potential applications in photovoltaic devices.
Generally, thin film solar cells are produced by attaching a thin layer of photovoltaic material onto silicon or a substrate.
The Cornell researchers were working with organic-inorganic metal halide perovskites, a class of photovoltaic materials with a distinctive crystal structure which has been extensively studied for solar applications for the past few years.
The research team created their near-perfect solar cells using a novel liquid source called non-halide lead acetate. Although perovskite-based solar cells have advanced significantly over the last few years, some of their basic characteristics still remain unknown.
For instance, fabrication of the solar materials begins with a solution of inorganic and organic molecules, which should be fine-tuned to obtain defect-free and smooth perovskite films. To date, this process has not been fully understood, leading to imperfections in the resulting materials.
To grow the solar cells, the researchers used several different liquid sources containing lead salts, and examined the role of certain anions on the formation of film. Then, using the Cornell High Energy Synchrotron Source, they observed how the crystal structures of perovskites differed based on which lead salt solution was utilized. This allowed them to identify the ideal starting solution.
By choosing the right precursor chemistry, and via a simple one-step solution casting process, we obtained perovskite films with a smoothness surpassing that of vapor-deposited films, resulting in record power conversion efficiencies.
Prof. Uli Wiesner
The paper, titled “Ultrasmooth Organic-Inorganic Perovskite Thin-Film Formation and Crystallization for Efficient Planar Heterojunction Solar Cells,” is a joint effort of Cambridge University, Oxford University, and Nanjing University in China, in addition to Cornell University.
This collaborative study was the outcome of a longstanding partnership between the Estroff and Wiesner laboratories at Cornell University, and their association with Henry Snaith at Oxford University, an expert in the fabrication of perovskite solar cell devices.
The work was supported by the National Science Foundation and the Kavli Institute at Cornell for Nanoscale Science.