Hybrid 2D [Pb(CH3NH2)I-2](n) Coordination Polymer Precursor for Scalable Perovskite Deposition

A two-dimensional hybrid coordination polymer Pb(CH3NH2)I-2 featuring a well-defined layered structure is reported for scalable perovskite ink and deposition. This coordination polymer exhibits structural, spectroscopic, and physicochemical properties distinct from common PbI2 perovskite precursors. Notably, it serves as a methylamine "gas carrier" capable of liberating methylamine (CH3NH2) into the precursor solution, thus improving the solubility of perovskite in unconventional, greener processing solvents, such as acetonitrile. The purity of Pb(CH3NH2)I-2 single crystals and the ability of the precursor to reduce sources of defects such as polyiodide species in solution allow the formation of high-quality perovskite films. This eventually results in efficient and stable devices, fabricated via a single-step antisolvent-free deposition method, transferable to large-area slot die coating. Gram scale synthesis of this unique lead precursor is demonstrated, essential for the scale-up of perovskite photovoltaic technology.

From Single-Crystals to High-Throughput

Jeannette Medina Kadro

Perovskite solar cells have undergone increase in power-conversion efficiencies at an unprecedented pace. Since their emergence in academic research in 2009, thousands of scientific papers have been published on their unique properties, variations cell architectures, material composition optimization and potential applications. In the course of this work, I attempted to cover multiple topics and focussed on applied research aspects. The first chapter describes a novel, rapid process for the growth of hybrid perovskite single crystals. Using minimal equipment and growth times, the solution-based process allows the fabrication of freestanding single crystals within minutes by heating stoichiometric precursor solutions. This efficient, simple process allowed me to produce single crystals in large amounts which, in turn, enabled me to develop a vacuum deposition technique for the preparation of perovskite thin films. Using rapid thermal flash vacuum deposition, thin films could be prepared with short deposition times and minimal manual sample preparation. The use of single crystals as sublimation precursors ensured stoichiometry of the deposit without the need for the challenging, precise control of multiple thermal sources. Another project covered in this thesis aimed to develop methods for high-throughput perovskite material screening or high-throughput research. Combinatorial libraries for the screening of perovskite compositions for optoelectronic applications were prepared by the vacuum deposition process also developed in the course of my PhD. Inkjet printing was also identified as suitable process and preliminary results are included in the last chapter of the thesis. The end-of-life and recycling of perovskite solar cells are covered in two chapters. A simple, highly selective dismantling process using orthogonal solvents is developed to reverse-engineer full solar cell devices and successful re-use of important device components is demonstrated. A detailed discussion of technological, environmental and regulatory challenges for the end-of-life management of perovskite solar panels is included as chapter three.

EPFL2018

From Single-Crystals to High-Throughput

Jeannette Medina Kadro

EPFL2018