Diseño y síntesis de semiconductores orgánicos de tipo p: hacia células solares de Perovskita eficientes

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, leída el 27-11-2020Perovskite solar cells (PSCs) have become one of the most promising technologies for searching clean alternatives to fossil fuels in order to achieve a sustainable society taking advantage of the unlimited solar energy. In a few years of research, PSCs have reached promising efficiencies up to 25% which are comparable to the commercial silicon-based cells. As a means to improve the efficiencies and the stability of PSCs, the research has been closely connected to the design of highly efficient charge selective layers such as electron (ETMs) and hole-transporting materials (HTMs). Although the charge selective layer could present either inorganic or polymeric structures, organic-based small molecules have been demonstrated as the most promising alternative for the preparation of highly efficient PSCs...Las células solares de perovskita (PSCs) se han convertido en una de las tecnologías más prometedoras en la búsqueda de alternativas limpias a los combustibles fósiles para alcanzar una sociedad sostenible aprovechando la energía solar ilimitada. En pocos años de investigación, PSCs han alcanzado eficiencias prometedoras por encima del 25% que son comparables a las células solares comerciales basadas en silicio. Con el fin de mejorar las eficiencias y la estabilidad de las PSCs, la investigación también ha estado relacionada con el diseño de capas selectivas de carga de alta eficiencia como los transportadores de electrones (ETMs) y de huecos (HTMs). Aunque las capas selectivas de carga pueden presentar una estructura inorgánica o polimérica, las moléculas orgánicas pequeñas han demostrado ser las alternativas más prometedoras para la preparación de PSCs de alta eficiencia..Fac. de Ciencias QuímicasTRUEunpu

Preparation of dipyrrins from F-BODIPYs by treatment with methanesulfonic acids

An alternative metal-free soft procedure for the preparation of dipyrrins from F-BODIPYs is reported. The new method makes possible to obtain certain dipyrrin derivatives that were unaccessible from F-BODIPYs to date. To demonstrate the ability of the new procedure, dipyrrins having highly reactive groups, such as chloro, cyano or acetoxyl, have been easily obtained from the corresponding F-BODIPY, which shows the synthetic utility of the reported methodology

High-Efficiency Perovskite Solar Cells using Molecularly-Engineered, Thiophene-Rich,Hole-Transporting Materials: Influence of Alkyl Chain Length on Power Conversion Efficiency

The synthesis and characterization of a series of novel small-molecule hole-transporting materials (HTMs) based on an anthra[1,2-b:4,3-b′:5,6-b′′:8,7-b′′′]tetrathiophene (ATT) core are reported. The new compounds follow an easy synthetic route and have no need of expensive purification steps. The novel HTMs were tested in perovskite solar cells (PSCs) and power conversion efficiencies (PCE) of up to 18.1 % under 1 sun irradiation were 2 measured. This value is comparable with the 17.8 % efficiency obtained using spiroOMeTAD as a reference compound. Similarly, a significant quenching of the Photoluminescence in the first nanosecond is observed, indicative of effective hole transfer.Additionally, the influence of introducing aliphatic alkyl chains acting as solubilizers on the device performance of the ATT molecules is investigated. Replacing the methoxy groups on the triarylamine sites by butoxy-, hexoxy- or decoxy-substituents greatly improved the solubility of the compounds without changing the energy levels, yet at the same time significantly decreasing the conductivity as well as the PCE, 17.3 % for ATT-OBu, 15.7 % for ATT-OHex and 9.7 % for ATT-ODec

Spiro-derivatives as hole transporting materials for improving the performance of perovskite solar cells

The Sun is the most powerful source of energy in the Earth's solar system, which, in part, can be exploited by all the inhabitants of the Earth. The optimal exploitation of the fraction that arrives on earth is, undoubtedly, among the most important challenges nowadays of science. To convert sun light into chemical energy, the first silicon-based device Photovoltaic (PV) solar cells, prepared by Chapin in 1954 exhibiting an efficiency around 6% [1,2] used different semiconducting materials (inorganic, organic, molecular, polymeric, hybrids, quantum dots, etc.). Today the most promising technology to replace/complement crystalline silicon PV [3] are the Perovskites solar cells (PSCs) that emerged since 2009, achieving efficiencies of ~26 %. These results were obtained using commercially available spiro-OMeTAD as hole-transporting material (HTM) that are expensive materials due to its difficult purification and multi-step synthetic protocols (in harsh conditions) which limits its future use in large-scale applications. Considering the negative aspects related to the industrial production of the spiro-OMeTAD, we synthesized some intermediates necessary for the subsequent synthesis of four spiro-derivatives. Excellent results were obtained with some derivatives based on electron-rich spiranic scaffolds [4], synthesized by the Buchwald-Hartwig reaction, carried out in toluene. In this way it was possible to obtain the spiro-PTZ functionalized, by making structural modifications to the previously obtained derivatives, the yield of this synthesis was around 21%. The compounds obtained were incorporated into perovskite solar cells providing efficiencies higher than the standard used (spiroOMeTAD). The devices have been tested under illumination and have shown good stability over time

A Trapezoidal Octacyanoquinoid Acceptor Forms Solution and Surface Products by Antiparallel Shape Fitting with Conformational Dipole Momentum Switch

A new compound (1) formed by two antiparallelly disposed tetracyano thienoquinoidal units has been synthesized and studied by electrochemistry, UV/Vis-NIR, IR, EPR, and transient spectroscopy. Self-assembly of 1 on a Au(111) surface has been investigated by scanning tunneling microscopy. Experiments have been rationalized by quantum chemical calculations. 1 exhibits a unique charge distribution in its anionic form, with a gradient of charge yielding a neat molecular in-plane electric dipole momentum, which transforms out-of-plane after surface deposition due to twisted! folded conformational change and to partial charge transfer from Au(111). Intermolecular van der Waals interactions and antiparallel trapezoidal shape fitting lead to the formation of an optimal dense on Au(111) two-dimensional assembly of 1. The realization of novel properties emerging upon electronic covalent coupling between chromophores (i.e., bichromophoric systems) is a critical issue for the development of photo- and electrically active systems.[1–3] In this regard, the relative topology and orientation of the p-subchromophores, such as in A + B type p-systems in Figure 1, with 1D linear conjugation, 2D parallel conjugation,[4] 3D orthogonal spiroconjugation[5] or 3D conjugation[6] are key factors. On the other hand, studies of the distribution of the excess of charge in p-conjugated moieties in post-electron transfer events are central issues in photophysics and photochemistry, in energy storage[7] and in organic electronics.[8] In addition to this electronic provision, its embedment in different molecular forms is of relevance as these can define unique ways of shape fitting in supramolecular and surface assemblies. Joint electronic and molecular shape designs thus allow to build molecular-based synthons in a tailored manner towards new bulk and nano organized materials. (...)Funding for open access charge: Universidad de Málaga / CBUA. The authors thank the Spanish Ministry of Science, Innovation and Universities MCIU (projects CTQ2017-83531-R, RED2018-102815-T, MAT2017-85089-C2-1-R), Centro de Excelencia Severo Ochoa grants (SEV-2016-0686, SEV2015-0496 and FUNFUTURE CEX2019-000917-S) and the CAM (QUIMTRONIC-CM project Y2018/NMT-4783). We thank MINECO/FEDER of the Spanish Government (projects PGC2018-098533-B-100 and PID2019-109555GB-I00), the Eusko Jaurlaritza (Basque Government, project PIBA19-0004) and the Junta de Andalucía, Spain (UMA18FEDERJA057). We also thank the Research Central Services (SCAI) of the University of Málaga and the Donostia International Physics Center (DIPC) Computer Center. We thank Dr. Juwon Oh and Prof. Donhgo Kim from the Spectroscopy Laboratory for Functional p-electronic Systems and Department of Chemistry, Yonsei University in Korea for the generous gift of the TRIR and UV/Vis transient absorption spectroscopy data

A Trapezoidal Octacyanoquinoid Acceptor Forms Solution and Surface Products by Antiparallel Shape Fitting with Conformational Dipole Momentum Switch

A new compound (1) formed by two antiparallelly disposed tetracyano thienoquinoidal units has been synthesized and studied by electrochemistry, UV/Vis-NIR, IR, EPR, and transient spectroscopy. Self-assembly of 1 on a Au(111) surface has been investigated by scanning tunneling microscopy. Experiments have been rationalized by quantum chemical calculations. 1 exhibits a unique charge distribution in its anionic form, with a gradient of charge yielding a neat molecular in-plane electric dipole momentum, which transforms out-of-plane after surface deposition due to twisted→folded conformational change and to partial charge transfer from Au(111). Intermolecular van der Waals interactions and antiparallel trapezoidal shape fitting lead to the formation of an optimal dense on Au(111) two-dimensional assembly of 1.The authors thank the Spanish Ministry of Science, Innovation and Universities MCIU (projects CTQ2017-83531-R, RED2018-102815-T, MAT2017-85089-C2-1-R), Centro de Excelencia Severo Ochoa grants (SEV-2016-0686, SEV-2015-0496 and FUNFUTURE CEX2019-000917-S) and the CAM (QUIMTRONIC-CM project Y2018/NMT-4783). We thank MINECO/FEDER of the Spanish Government (projects PGC2018-098533-B-100 and PID2019-109555GB-I00), the Eusko Jaurlaritza (Basque Government, project PIBA19-0004) and the Junta de Andalucía, Spain (UMA18FEDERJA057). We also thank the Research Central Services (SCAI) of the University of Málaga and the Donostia International Physics Center (DIPC) Computer Center. We thank Dr. Juwon Oh and Prof. Donhgo Kim from the Spectroscopy Laboratory for Functional π-electronic Systems and Department of Chemistry, Yonsei University in Korea for the generous gift of the TRIR and UV/Vis transient absorption spectroscopy data.Peer reviewe

Design and synthesis of organic p-type semiconductors: toward efficient Perovskite Solar Cells

Perovskite solar cells (PSCs) have become one of the most promising technologies for searching clean alternatives to fossil fuels in order to achieve a sustainable society taking advantage of the unlimited solar energy. In a few years of research, PSCs have reached promising efficiencies up to 25% which are comparable to the commercial silicon-based cells. As a means to improve the efficiencies and the stability of PSCs, the research has been closely connected to the design of highly efficient charge selective layers such as electron (ETMs) and hole-transporting materials (HTMs). Although the charge selective layer could present either inorganic or polymeric structures, organic-based small molecules have been demonstrated as the most promising alternative for the preparation of highly efficient PSCs..

Speeding up heterogeneous catalysis with an improved highly reusable catalyst for the preparation of enantioenriched secondary alcohols

A new catalytic heterogeneous system, very efficient and highly reusable, for the preparation of enantioenriched secondary alcohols through the addition of diethylzinc to benzaldehyde has been developed. This system is based on a chiral bis(hydroxyamide) ligand supported on crosslinked polystyrene. The catalyst has been shown to be very efficient, leading to the corresponding secondary alcohol with an enantiomeric excess of 93% in a time as short as 2 h and using just 4% of the heterogeneous catalyst and just 1.5 equivalents of the organozinc reagent. We have demonstrated that the new catalyst is very stable and can be efficiently recycled with no decrease in yield or enantioselectivity. The presented system has an unquestionable interest for the potential transfer of the reaction to the industry by using catalytic fluidized-bed reactors

Saddle-like, π-conjugated, cyclooctatetrathiophene-based, hole-transporting material for perovskite solar cells

A flexible, saddle-like, π-conjugated skeleton composed of four fused thiophene rings forming a cyclooctatetrathiophene (CoTh) with four triphenylamines (CoTh-TTPA) is presented as a hole-transporting material (HTM) for perovskite solar cells. The new HTM shows a bright red color stemming from a direct conjugation between the TPA groups and the central CoTh scaffold. This results in a charge transfer band due to the combination of the weak acceptor moiety, the CoTh unit, and the electron-donating p-methoxytriphenylamine groups. CoTh-TTPA exhibits a suitable highest-occupied molecular orbital (HOMO) level in relation to the valence band edge of the perovskite, which ensures efficient hole extraction at the perovskite/HTM interface. It has been applied as the HTM in combination with a mixed perovskite ([FAPbI3]0.85[MAPbBr3]0.15) and a state-of-the-art triple cation perovskite ([(FAPbI3)0.87(MAPbBr3)0.13]0.92[CsPbI3]0.08) reaching noticeable light-to-energy conversion efficiencies of 16.3 and 15.9%, respectively. These values are slightly lower than those measured for the benchmark spiro-OMeTAD HTM. The HTM properties have been analyzed by means of photoluminescence and conductivity experiments, which demonstrated a better hole extraction and conductivity for spiro-OMeTAD