Tunable Wide‐Bandgap Monohalide Perovskites

2020

Herein the mechanochemical synthesis of inorganic as well as hybrid organic-inorganic monohalide perovskites with tunable bandgaps is reported. It is shown that the bandgap bowing known for iodide mixed Sn-Pb perovskites is also present in the pure bromide analogous. This results in technologically very interesting materials with bandgaps in the range of 1.7-1.9 eV. Similar bandgap perovskites are typically achieved by mixing two halides that are prone to segregate over time. This limits the achievable open circuit voltage. For monohalide perovskites this problem is eliminated, making these materials especially promising wide bandgap absorbers for tandem solar cells. Perovskite Thin-film Ph…

Vacuum-Deposited Multication Tin-Lead Perovskite Solar Cells

2020

The use of a combination of tin and lead is the most promising approach to fabricate narrow bandgap metal halide perovskites. This work presents the development of reproducible tin and lead perovskites by vacuum co-deposition of the precursors, a solvent-free technique which can be easily implemented to form complex stacks. Crystallographic and optical characterization reveal the optimal film composition based on cesium and methylammonium monovalent cations. Device optimization makes use of the intrinsically additive nature of vacuum deposition, resulting in solar cells with 8.89% photovoltaic efficiency. The study of the devices by impedance spectroscopy identifies bulk recombination as on…

Electrochemical Synthesis of Hybrid Layered Thermoelectric Materials Based on PEDOT/SnS Doped with Ag

2021

Perovskite Solar Cells: Stable under Space Conditions

2020

Metal halide perovskite solar cells (PSCs) are of interest for high altitude and space applications due to their lightweight and versatile form factor. However, their resilience toward the particle spectrum encountered in space is still of concern. For space cells, the effect of these particles is condensed into an equivalent 1 MeV electron fluence. The effect of high doses of 1 MeV e-beam radiation up to an accumulated fluence to 10^16 e-cm-2 on methylammonium lead iodide perovskite thin films and solar cells is probed. By using substrate and encapsulation materials that are stable under the high energy e-beam radiation, its net effect on the perovskite film and solar cells can be studied.…

Room temperature vacuum-deposition of CsPbI2Br perovskite films from multiple-sources and mixed halide precursors

2020

Fully inorganic cesium lead halide perovskites, such as CsPbI2Br, show enhanced thermal stability compared to hybrid ones and are being widely investigated as wide bandgap absorbers for tandem applications. Despite their simple stoichiometry, the preparation of highly crystalline and stable cesium lead halide thin films is not trivial. In general, high-efficiency solar cells based on solution-processed CsPbI2Br thin films are prepared by hightemperature annealing or the use of chemical additives. In this work, we use solvent-free synthesis to investigate the formation of CsPbI2Br in bulk or in thin films via mechanochemical synthesis and multiple-source vacuum deposition, respectively. We d…

Manufacturing Te/PEDOT Films for Thermoelectric Applications

2017

In this work, flexible Te films have been synthesized by electrochemical deposition using PEDOT [poly(3,4-ethylenedioxythiophene)] nanofilms as working electrodes. The Te electrodeposition time was varied to find the best thermoelectric properties of the Te/PEDOT double layers. To show the high quality of the Te films grown on PEDOT, the samples were analyzed by Raman spectroscopy, showing the three Raman active modes of Te: E1, A1, and E2. The X-ray diffraction spectra also confirmed the presence of crystalline Te on top of the PEDOT films. The morphology of the Te/PEDOT films was studied using scanning electron microscopy, showing a homogeneous distribution of Te along the film. Also an a…

FAPb0.5Sn0.5I3: A Narrow Bandgap Perovskite Synthesized through Evaporation Methods for Solar Cell Applications

2020

The tunability of the optoelectrical properties upon compositional modification is a key characteristic of metal halide perovskites. In particular, bandgaps narrower than those in conventional lead‐based perovskites are essential to achieve the theoretical efficiency limit of single‐absorber solar cells, as well as develop multijunction tandem devices. Herein, the solvent‐free vacuum deposition of a narrow bandgap perovskite based on tin-lead metal and formamidinium cation is reported. Pinhole‐free films with 1.28 eV bandgap are obtained by thermal codeposition of precursors. The optoelectrical quality of these films is demonstrated by their use in solar cells with a power conversion effici…

Hansen theory applied to the identification of nonhazardous solvents for hybrid perovskite thin-films processing

2018

Abstract Metal-halide perovskites have become the most studied material for efficient next-generation solar cells, in part because of the possibility of depositing high quality semiconducting perovskites by simple solution-based methods. However, the majority of solvent systems implemented in literature for deposition of lead halide perovskites are hazardous to handle. Investigation of alternatives perovskite processing methods are hence key to safely upscale the perovskite photovoltaic manufacturing. In this manuscript we use the Hansen theory to find suitable nonhazardous solvents to solubilize two lead salts, PbBr2 and PbI2, used to fabricate the corresponding methylammonium (MA) lead ha…

Vacuum Processed Narrow and Wide Bandgap Perovskites for Photovoltaic Applications

2021

El objetivo principal de la presente tesis fue el desarrollo de nuevos materiales que sirvan de ayuda en la actual emergencia climática. De este modo, se prepararon perovskitas de banda prohibida estrecha y ancha con la intención de integrarlas en tándems, que pueden aprovechar todo el espectro solar para generar energía, en el futuro. Las perovskitas fueron preparadas mediante la técnica de sublimación, o deposición a vacío. Además, se emplearon otras técnicas que no requieren del uso de disolventes, como la mecanoquímica. A lo largo de la tesis se preparan dos perovskitas de banda prohibida estrecha, siendo una de ellas la primera perovskita basada en plomo y estaño sintetizada mediante s…