Periodic Reporting for period 1 - HT PHOTO DB (High throughput computing for accelerated photovoltaic material discovery: From materialdatabase to the new generation of photovoltaic materials.)
Okres sprawozdawczy: 2018-04-01 do 2020-03-31
From late 1970s to the early 2000s, the efficiency of traditional photovoltaics, PV, cells based on single crystal Si, GaAs or CdTe has evolved from 8-13% to 25% approximately. Since then, the improvement of the efficiency of these classic solar cells based on p-n junctions seem to have found a ceiling. The discouraging progress during the last decade stems from the limited photovoltage of solar cells based on p-n junctions due to the band gap of the semiconductor and the Shockley-Queisser, S-L, limit. In order to make this technology more competitive, significant improvements must be made in their efficiency by the discovery of new photovoltaic mechanisms that overcome the aforementioned issues. Ferroelectric materials, which present a spontaneous electric polarization, exhibit a different behavior under photo-excitation, providing an alternative way to separate carriers. This is called the bulk photovoltaic effect, which has reinvigorated efforts for the development of new solar cells, now based on ferroelectric materials.
Hybrid perovskite thin-films such as CH3NH3PbI3, MAPbI3, have changed the solar cell field in recent years because of their low cost and high efficiency. However, their low stability and durability have hampered their implementation in the market. Chalcohalides have been recently proposed as an alternative, but they usually exhibit a lower polarization than other ferroelectric materials. Oxide perovskites stand as the most promising candidates because their strong polarization and high thermal, mechanical and chemical stabilities are combined with very low costs for their synthesis. Oxide perovskites also present issues that will need to be overcome to design efficient PV devices, their wide band gap being the main obstacle.
Different strategies have been proposed to tailor the electronic properties of these oxides, reducing the band gap from 2 eV–3 eV to 1.5 eV. The epitaxial growth of strained thin-film oxides, promoting the rhombohedral-to-tetragonal phase transition or doping of both A and B sites are effective approaches to reduce the band gap of these oxides. Theoretical works, most of them based on density functional theory, DFT, calculations, have helped to understand the electronic and structural properties of ferroelectric oxides. However, the optimization of solar cells based on ferroelectric materials requires the screening of too many variables. This challenge can be tackled combining DFT calculations with high-throughput frameworks and the use of materials database.
HT-PHOTO-DB project has developed and used high-throughput frameworks and materials databases for accelerating the discovery of new materials for more efficient solar cells based on ferroelectric oxides.
Hybrid perovskite thin-films such as CH3NH3PbI3, MAPbI3, have changed the solar cell field in recent years because of their low cost and high efficiency. However, their low stability and durability have hampered their implementation in the market. Chalcohalides have been recently proposed as an alternative, but they usually exhibit a lower polarization than other ferroelectric materials. Oxide perovskites stand as the most promising candidates because their strong polarization and high thermal, mechanical and chemical stabilities are combined with very low costs for their synthesis. Oxide perovskites also present issues that will need to be overcome to design efficient PV devices, their wide band gap being the main obstacle.
Different strategies have been proposed to tailor the electronic properties of these oxides, reducing the band gap from 2 eV–3 eV to 1.5 eV. The epitaxial growth of strained thin-film oxides, promoting the rhombohedral-to-tetragonal phase transition or doping of both A and B sites are effective approaches to reduce the band gap of these oxides. Theoretical works, most of them based on density functional theory, DFT, calculations, have helped to understand the electronic and structural properties of ferroelectric oxides. However, the optimization of solar cells based on ferroelectric materials requires the screening of too many variables. This challenge can be tackled combining DFT calculations with high-throughput frameworks and the use of materials database.
HT-PHOTO-DB project has developed and used high-throughput frameworks and materials databases for accelerating the discovery of new materials for more efficient solar cells based on ferroelectric oxides.
The work performed in this project can be divided in two main blocks:
I. Development of high-throughput frameworks and data mining. Different strategies have been designed combining DFT calculations, materials data bases and high-throughput techniques to accelerate the discovery of new systems with application in photovoltaics.
II. Ferroelectrics materials modeling. The aforementioned frameworks have been applied to the optimization of new ferroelectric materials with potential applications in solar cells.
Dissemination effort has been designed based on open science:
I. All the high-throughput frameworks are available in Zenodo and Github repositories
II. Publications are also accesible through ChemRxiv
III. Data is freely available at io-Chem BD
IV. The initiative NewMaterialsLab was created to increase the visibility of the communication and dissemination actions, including a website (www.newmaterialslab.com) and a Twitter account (NewMaterialsLab)
VI. Participations with oral presentations in conferences and workshops have also been part of the dissemination plan.
I. Development of high-throughput frameworks and data mining. Different strategies have been designed combining DFT calculations, materials data bases and high-throughput techniques to accelerate the discovery of new systems with application in photovoltaics.
II. Ferroelectrics materials modeling. The aforementioned frameworks have been applied to the optimization of new ferroelectric materials with potential applications in solar cells.
Dissemination effort has been designed based on open science:
I. All the high-throughput frameworks are available in Zenodo and Github repositories
II. Publications are also accesible through ChemRxiv
III. Data is freely available at io-Chem BD
IV. The initiative NewMaterialsLab was created to increase the visibility of the communication and dissemination actions, including a website (www.newmaterialslab.com) and a Twitter account (NewMaterialsLab)
VI. Participations with oral presentations in conferences and workshops have also been part of the dissemination plan.
"The progress of this project is focused in three different topics, all of them related to development of ferroelectric materials for solar cells applications:
Band gap engineering using interfaces. The main goal of this part of the project work has been providing a new approach to accelerate the design of new solar cells based on thin-film ferroelectric oxides. Computational materials databases have been combined with a high-throughput mismatch calculator to identify potential substrates for the epitaxial growth of KNbO3 thin-films. These substrates were used to build interface models which have been studied by means of density functional theory. The influence of lattice mismatch and band alignment were analyzed to reduce KNbO3 band gap and optimize the electron injection between both surfaces. Once the large multidimensional search space has been reduced using databases and screening DFT calculations, the potential candidates are explored in detail with more computationally demanding models. Please see: https://pubs.rsc.org/en/content/articlelanding/2019/ta/c9ta11820a/unauth#!divAbstract. This study is a good example of how computational materials databases combined with first principles calculations are, together, excellent tools in spurring the development of new solar cell devices, reducing the variables that need to be explored experimentally.
Doped perovskites oxides as photovoltaic materials. Solids solutions are relevant systems for a wide variety of technologies. However, they are complex materials whose properties depend on many variables such as dopant concentration, synthesis method or temperature. This complexity is even greater when more than one property has to be monitored. This is the case of doped ferroelectric materials, where band gap and polarization need to be optimized. In this project, we have developed a framework to study doped ferroelectric materials combining Boltzmann statistics and DFT calculations. This approach presents two main advantages: i) the automatic and systematic exploration of the configurational space and ii) the connection between the changes in the microstructure of the material and its photovoltaic performance. We believe that this framework could be used as an efficient tool to strengthen the connection between theoretical and experimental results, thus accelerating the discovery, design, and optimization of new doped photosensitized ferroelectric materials.
Photoinduced ferroelectricity. SrTiO3, STO, is probably the one of the most studied oxide perovskites. Its structure and optoelectronic properties have been experimentally and theoretically analyzed in many works. As a consequence, how to modify their band structure to tailor its band gap is well known. Unfortunately, SrTiO3 is paraelectric and centrosymmetric even at very low temperatures. Here, the challenge is not to reduce the band gap but to induce a ferroelectric behavior to the oxide. We have explained how it is possible to observe a photocurrent in STO photoinducing ferrolectricity."
Band gap engineering using interfaces. The main goal of this part of the project work has been providing a new approach to accelerate the design of new solar cells based on thin-film ferroelectric oxides. Computational materials databases have been combined with a high-throughput mismatch calculator to identify potential substrates for the epitaxial growth of KNbO3 thin-films. These substrates were used to build interface models which have been studied by means of density functional theory. The influence of lattice mismatch and band alignment were analyzed to reduce KNbO3 band gap and optimize the electron injection between both surfaces. Once the large multidimensional search space has been reduced using databases and screening DFT calculations, the potential candidates are explored in detail with more computationally demanding models. Please see: https://pubs.rsc.org/en/content/articlelanding/2019/ta/c9ta11820a/unauth#!divAbstract. This study is a good example of how computational materials databases combined with first principles calculations are, together, excellent tools in spurring the development of new solar cell devices, reducing the variables that need to be explored experimentally.
Doped perovskites oxides as photovoltaic materials. Solids solutions are relevant systems for a wide variety of technologies. However, they are complex materials whose properties depend on many variables such as dopant concentration, synthesis method or temperature. This complexity is even greater when more than one property has to be monitored. This is the case of doped ferroelectric materials, where band gap and polarization need to be optimized. In this project, we have developed a framework to study doped ferroelectric materials combining Boltzmann statistics and DFT calculations. This approach presents two main advantages: i) the automatic and systematic exploration of the configurational space and ii) the connection between the changes in the microstructure of the material and its photovoltaic performance. We believe that this framework could be used as an efficient tool to strengthen the connection between theoretical and experimental results, thus accelerating the discovery, design, and optimization of new doped photosensitized ferroelectric materials.
Photoinduced ferroelectricity. SrTiO3, STO, is probably the one of the most studied oxide perovskites. Its structure and optoelectronic properties have been experimentally and theoretically analyzed in many works. As a consequence, how to modify their band structure to tailor its band gap is well known. Unfortunately, SrTiO3 is paraelectric and centrosymmetric even at very low temperatures. Here, the challenge is not to reduce the band gap but to induce a ferroelectric behavior to the oxide. We have explained how it is possible to observe a photocurrent in STO photoinducing ferrolectricity."