📰 Optimize solar cell performance

Controlling the microstructure of halogenated hybrid perovskite thin films used in solar cells is crucial to optimize their performance. Irig researchers are interested in the deformation state of perovskite films by diffraction (Diffraction is the behavior of waves when they hit an obstacle that isn’t theirs…) X-rays and study themorientation (In the literal sense, orientation denotes or materializes the direction of the east (sunrise…) out network (A computer network is a set of devices connected to share information…) Crystalline through in these films microscopy (Microscopy is the observation of a specimen (placed in a microscopic slide…) X-ray diffraction. The stability of the different orientations of the domains is examined by DFT and illustrates the determining role of thevicinity (The environment is everything that surrounds us. It is all natural elements and…) chemicalinterface (An interface is a real or virtual area that separates two elements. The interface…) film substrate.

In which context (The context of an event includes the circumstances and conditions surrounding it; the…) the development of photovoltaic technologies based on solar cells Halogenated hybrid perovskites (PHH) do thatobject (In general, the word object (from Latin objectum, 1361) denotes an entity defined in ….) intensive studies for ten years. These cells are now achieving energy conversion efficiencies approaching those of solar cells silicon (Silicon is a chemical element from the crystallogene family, symbol Si…), of the order of 25.5%. However, there are still many challenges to be overcome in order to reach the performance of silicon, especially in terms of the stability of performance in the time (Time is a concept developed by humans to represent the…)Stability, which requires, among other things, the championship (The master’s degree is a higher education degree or diploma equivalent to the degree or title of…) structural properties of thin layers by PHH. However, questions remain, such as the stress state of the crystal lattice that makes up these thin layers of PHH and its orientation.

It is well known that the deformation state of the perovskite layer affects its stability, just like the orientation of the crystal lattice possibly affects the optoelectronic properties of the perovskite. With regard to the control of microstructure thin layers of PHH, Irig researchers used laboratory X-ray diffraction (XRD) and diffraction X-ray microscopy synchrotron (The term synchrotron refers to a large electromagnetic instrument designed to…) to identify and understand the mechanisms that determine the strain state and crystal orientation of MAPbI thin films3 one of materials (A material is a material of natural or artificial origin that man molds into…) Reference PHH.

Initially, the Irig researchers were interested in the deformation state of perovskite films. To do this, they carried out XRD measurements on site which allowed them to challenge the commonly accepted assumption that PHH films synthesized at 100 °C exhibit strain at temperature (Temperature is a physical quantity that is measured with a thermometer and…) Surroundings due to the difference between the values ​​of coefficient of expansion (Coefficients of expansion measure the relative increase in volume of a system if…) thermal (Thermie is the science that deals with the production of energy, the use of…) (CDT) of the PHH and the substrate on which the thin films are deposited. Indeed, their measurements have revealed the possibility of obtaining thin layers of MAPbI3 Completely (Completion or fully automatic, or by Anglicism completion or…) relaxed (without deformations), demonstrating the lack of a direct correlation between the difference in CTE and the deformation of the thin films.

In a second step, the researchers examined the alignment of the crystal lattice in these thin layers using X-ray diffraction microscopy at the European synchrotron radiation (Radiation is a transfer of energy in the form of waves or particles that can be…) Facility (ESRF in Grenoble), a technique that makes it possible to visualize all the crystalline areas that have the same orientation. Their results made it possible to attribute the origin of the double texture sometimes observed in XRD measurements to the presence of Twins ferroelastic (picture) see training (In intonation, fundamental frequency changes are perceived as variations of….) during the cubic-tetragonal structure transition of MAPbI3 about 57 degrees.


A twin is a union of several identical crystals whose orientations are not arbitrary, but are connected by operations symmetry (In general, the term symmetry refers to existence in a…) Properties of the crystal structure of material (A material is a material of natural or man-made origin that man shapes…) questionable.

Finally, these experimental investigations were supplemented by calculations theory (The word theory comes from the Greek word theorein, which means “consider, observe,…”) of functional (In mathematics, the term functional refers to specific functions….) of density (The density or specific gravity of a body is the ratio of its density to…) (DFT) showing that the chemical environment at the interface to the substrate (“first layer” of the MAPbI network3 MAI or PbI type2) influences the orientation of the perovskite.

These different results represent an important advance in the understanding of the microstructure of the layers of halogenated hybrid perovskites and open the way to control their stress state and texture with the aim of improving their optoelectronic properties as well as the performances and device stability.

That Halogenated hybrid perovskites to have a together (In set theory, a set intuitively denotes a collection…) Favorable properties for photovoltaics, rarely present in other types of materials at the same time: a big one coefficient (In mathematics, a coefficient is a multiplicative factor that depends on a specific….) fromabsorption (In optics, absorption describes the process in which the energy of a photon is absorbed…)weak excitonic effects, energy (In a general sense, energy means anything that enables you to do work, gain energy, etc.) of banned bands that allow for a good collection of the photons (In particle physics, the photon is the mediating elementary particle of the interaction…)good qualities of transport (Transportation is the act of transporting something or someone from one place to another, most…), high fault tolerance. In addition, these physical properties can be modulated as a result engineering (Engineering refers to all functions ranging from design and studies to….) Chemical that allows perovskites to be optimized to adapt them to the various photovoltaic challenges such as stability or the manufacture of multi-cells.

The texture of a thin layer characterizes the orientation of the crystal lattice in the direction upright (In plane geometry, two lines are said to be perpendicular if they intersect at ….) in the layer plane.
That microstructure a crystalline thin film is defined by the stress state, the texture and the length (The length of an object is the distance between its two extreme ends…) Crystal lattice coherence.

References:
Medjahed AA, Zhou T, Alvarez Quiceno JC, Dally P, Pochet P, Schülli TU, Djurado D, Reiss P, and Pouget S
Microstructure of Methylammonium Lead Iodide Perovskite Thin Films: A Comprehensive Strain and Texture Study.
Advanced energy materials2022.

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