23 research outputs found
Design and Synthesis of Small Molecules for Organic and Grätzel Solar Cells
El creixement de la poblaciĂł i dels nous paĂŻsos emergents fa que el consum energètic es dispari. Tota la poblaciĂł depèn dâaquest consum i com a conseqßència es depèn de les reserves de combustibles fòssils disponibles.
Una de les fonts dâenergia no esgotable i que proveu a la terra dâuna gran quantitat dâenergia es el Sol. Aquesta Energia ja estĂ sent explotada amb la utilitzaciĂł de panells solars basades en silici. No obstant degut al seu alt cost de fabricaciĂł no poden competir amb les fonts dâenergia ja existents. Per tant, noves investigacions en alternatives han estat Ă mpliament estudiades.
Unes de les alternatives que han estat Ă mpliament estudiades durant aquests anys han estat les cel¡les sensitivitzades amb colorant (DSSC) i les cel¡les orgĂ niques (OPV). Les bases i el funcionament dâaquests dos tipus de dispositius es mostren en el capĂtol 1.
El principal estudi dâaquesta tesis es centra en el disseny i la sĂntesis de nous colorants per aquest tipus de dispositius. Aquests colorants tenen un paper molt important en aquests dispositius i moltes vegades la seva eficiència deriva de lâestructura dâaquests colorants degut a les reaccions que es produeixen en els dispositius.
En el CapĂtol 3 i 4 es presenta el disseny de dos tipus de colorants pel que fa a les cel¡les sensitivitzades amb colorant (DSSC). En el capĂtol 3 es tracta de noves molècules orgĂ niques amb estructura D-Ď-A Ă mpliament estudiades com a alternativa als complexes de ruteni. En el capĂtol 4 les molècules sintetitzades tambĂŠ per DSSC sĂłn una famĂlia de porfirines, les quals sĂłn les que actualment estan mostrant mĂŠs eficiència.
Per una altra banda en el capĂtol 5 sâha sintetitzat tambĂŠ una porfirina però en aquest cas per estudiar la seva aplicabilitat en les cel¡les solars orgĂ niques (OPV).El Crecimiento de la poblaciĂłn I de nuevos paĂses emergentes hace que el consume energĂŠtico se dispare. Toda la poblaciĂłn depende de este consume I como consecuencia se depende de las reservas de combustibles fĂłsiles disponibles.
Una de las Fuentes de energĂa no agotable y que suministra a la tierra de una gran cantidad de energĂa es el Sol. Esta energĂa ya estĂĄ siendo explotada con la utilizaciĂłn de paneles solares basados en Silicio. Sin embargo, debido a su elevado coste de fabricaciĂłn no pueden competir con fuentes de energĂa ya existentes. Por lo tanto, nuevas investigaciones en alternativas han estado estudiadas.
Una de las alternativas que han sido mĂĄs estudiadas son las Celdas sensitibizadas con colorante (DSSC) i las Celdas OrgĂĄnicas (OPV). Las bases y su funcionamiento se muestran en el capĂtulo 1.
El principal estudio de esta tesis se centra en el diseĂąo y la sĂntesis de nuevos colorantes para estos tipos de dispositivos. Estos colorantes tienen un papel muy importante en estos dispositivos y muchas veces su eficiencia deriva de la estructura del colorante debido a reacciones que se producen en el dispositivo.
En el CapĂtulo 3 y 4 se presenta el diseĂąo de dos tipos de colorantes para las celdas sensitibizadas con colorante. En el CapĂtulo 3 se muestran molĂŠculas orgĂĄnicas con estructura D--A que han sido ampliamente estudiadas como alternativa a los complejos de rutenio. En el capĂtulo 4 una familia de porfirinas ha sido sintetizada debido a los prometedores resultados mostrados siendo en la actualidad las molĂŠculas que dan mĂĄs eficiencia.
En el CapĂtulo 5 en cambio se ha sintetizado una porfirina, pero en este caso para estudiar su aplicabilidad en las celdas orgĂĄnicas (OPV)The population is growing and the consumption of energy is dramatically increasing. All the population depends on this energy and are using fossil fuels available.
One of this renewable source that gives to the earth a huge amount of energy is the sun. This source is exploited nowadays with photovoltaic devices based in silicon. However due to their high cost of production is not an alternative comparing with the existent sources. For this reason scientists of the entire world are working hard in the development of alternative devices in order to reduce the cost, decrease the contamination and increase the efficiencies among others.
Some of alternatives that have been widely studied during the last years have been the Dye Sensitized Solar Cells (DSSC) and Organic Solar Cells (OPV). Basic principles of these devices are showed in Chapter 1.
Principally the study of this thesis was focused in the design and synthesis of new sensitizers for these devices. These sensitizers play an important role in these devices and many times their structure depends on the efficiency of the device.
In Chapter 3 and 4 the design and synthesis of two kinds of sensitizers and their applicability in DSSC is showed. In chapter 3 the sensitizers are organic dyes with a structure of D-Ď-A widely studied as alternative to the ruthenium complexes. In chapter 4 another family of sensitizers have been synthesized and also their applicability in DSSC has been studied. In this chapter the molecules are a family of porphyrins that are the molecules that nowadays are showing the most efficiency.
On the other hand in Chapter 5 a new porphyrin has been synthesized but in this case to study their applicability in Organic solar Cells (OPV
Diarylamino-substituted Tetraarylethene (TAE) as Efficient and Robust Hole Transport Material for 11% Methyl Ammonium Lead Iodide Perovskite Solar Cells.
We report the synthesis and characterisation of tetra{4-[N,N-(4,4â˛-dimethoxydiphenylamino)]phenyl}ethene (TAE-1) as an efficient and robust hole transport material for its application in methyl ammonium lead iodide (MAPI) perovskite solar cells. The solar cells show light-to-energy conversion efficiencies as high as 11.0% under standard measurement conditions without the need of additional dopants
Synthesis, optical and electrochemical properties of the AâĎ-DâĎ-A porphyrin and its application as an electron donor in efficient solution processed
A conjugated acceptor–donor–acceptor (A–π-D–π-A) with the Zn-porphyrin core and the di-cyanovinyl substituted thiophene (A) connected at meso positions denoted as VC62 was designed and synthesized. The optical and electrochemical properties of VC62 were investigated. This new porphyrin exhibits a broad and intense absorption in the visible and near infrared regions. Bulk-heterojunction (BHJ) solution processed organic solar cells based on this porphyrin, as electron donor material, and PC71BM ([6,6]- phenyl C71 butyric acid methyl ester), as electron acceptor material, were fabricated using THF and a pyridine– THF solvent exhibiting a power conversion efficiency of 3.65% and 5.24%, respectively. The difference in efficiencies is due to the enhancement of the short circuit current Jsc and FF of the solar cell, which is ascribed to a stronger and broader incident photon to current efficiency (IPCE) response and a better balanced charge transport in the device processed with the pyridine–THF solvent</div
A single atom change âswitches-onâ the solar-to-energy conversion efficiency of Zn-porphyrin based dye sensitized solar cells to 10.5%
In this work we report how crucial is the correct design of the porphyrin sensitizers in Dye Sensitized Solar Cells (DSSCs). Only a single atom change switches-on the efficiency from 2–3% to over 10% under standard measurement conditions. We used the 2,1,3-benzothiadazole (BDT) group, as a p-conjugated linker, for the porphyrin LCVC01, a thiophene moiety for the porphyrin LCVC02 and also the furan group for the LCVC03 porphyrin, as molecular spacers between the BDT fragment and the molecule anchoring group, respectively. These three porphyrins were investigated for their application in DSSC devices. All the devices were characterized and found to achieve a record cell efficiency of 10.5% for LCVC02 but only 3.84% and 2.55% for LCVC01 and LCVC03 respectively. On one hand, the introduction of a thiophene, instead of a furan group, illustrates the importance of introducing a chemical group as a spacer, such as thiophene, between the BDT and the anchoring group. On the other hand, the selection of this group has to be correct because the change of a single atom increases the charge recombination rate and decreases the device performance. These changes can be rationalized by analyzing the dye dipoles and their interactions.</div
A single atom change âswitches-onâ the solar-to- energy conversion efficiency of Zn-porphyrin based dye sensitized solar cells to 10.5%
In this work we report how crucial is the correct design of the porphyrin sensitizers in Dye Sensitized Solar Cells (DSSCs). Only a single atom change switches-on the efficiency from 2â3% to over 10% under standard measurement conditions. We used the 2,1,3-benzothiadazole (BDT) group, as a p-conjugated linker, for the porphyrin LCVC01, a thiophene moiety for the porphyrin LCVC02 and also the furan group for the LCVC03 porphyrin, as molecular spacers between the BDT fragment and the molecule anchoring group, respectively. These three porphyrins were investigated for their application in DSSC devices. All the devices were characterized and found to achieve a record cell efficiency of 10.5% for LCVC02 but only 3.84% and 2.55% for LCVC01 and LCVC03 respectively. On one hand, the introduction of a thiophene, instead of a furan group, illustrates the importance of introducing a chemical group as a spacer, such as thiophene, between the BDT and the anchoring group. On the other hand, the selection of this group has to be correct because the change of a single atom increases the charge recombination rate and decreases the device performance. These changes can be rationalized by analyzing the dye dipoles and their interactions
Efficient bulk heterojunction solar cells based on solution processed small molecules based on the same benzo[1,2-b:4, 5-bâ]thiophene unit as core don
We report the synthesis, characterization, and optical and electrochemical of properties of two novel molecules DRT3-BDT (1) and DTT3-BDT (2), comprising the same BDT central core (donor) and different end capped acceptor units, i.e. rhodanine with ethyl hexyl and thiazolidione with ethylhexyl, respectively, linked via an alkyl-substituted terthiophene (3 T) π-conjugation bridge. The electrochemical properties of these small molecules indicate that their energy levels are compatible with energy levels of PC71BM for efficient exciton dissociation. These molecules have been used as electron donors along with PC71BM as an electron acceptor, for the fabrication of solution processed “small molecule” bulk heterojunction (BHJ) solar cells (smOPV). The device prepared from optimized 1:PC71BM(1:1) processed cast from DIO (3%v)/CF solvent exhibited a power conversion efficiency of 6.76% with Jsc = 11.92 mA cm−2, Voc = 0.90 and FF = 0.63. The device with 2:PC71BM under the same conditions showed a lower PCE of 5.25% with Jsc = 10.52 mA cm−2, Voc = 0.86 and FF = 0.56. The AFM, TEM and PL quenching measurements revealed that the high Jsc is a result of the appropriate morphology and exciton dissociation. The performances were compared for the devices based on two small molecules. The higher Jsc for device 1 was attributed to its better nanoscale phase separation, smooth surface and higher carrier mobility in the 1:PC71BM blend film. Moreover, the higher value of FF for the 1:PC71BM based device was ascribed to a good balance between the electron and hole mobilities. <img alt="Graphical abstract: Efficient bulk heterojunction solar cells based on solution processed small molecules based on the same benzo[1,2-b:4, 5-bâ˛]thiophene unit as core donor and different terminal units" id="imgGALoader" src="http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=C5NR01037C" style="border: 0px;" title="Gra
Solution processed organic solar cells based on Aâ DâD0âDâA small molecule with benzo[1,2-b:4,5-b0] dithiophene donor (D0) unit, cyclopentadithiophene
Solution processed small molecule A–D–D0–D–A, denoted as BDT(CDTRH)2, consists of 2-ethylhexoxy substituted BDT (donor D' unit) as the central building block and 3-ethylrhodanine (RH) as the end capped terminal (acceptor group) unit, with a p-linkage of cyclopentadithiophene (CDT) (donor D). We have designed and synthesized it, and we have investigated its optical and electrochemical properties, finding that its energy levels are compatible with the energy levels of fullerene derivatives for efficient exciton dissociation. This small molecule has been used as an electron donor along with PC71BM as the electron acceptor for the fabrication of solution processed small molecule bulk heterojunction (BHJ) solar cells. The BHJ solar cell processed with BDT(CDTRH)2 : PC71BM (1 : 1 wt ratio) showed a power conversion efficiency (PCE) of 4.58% with Jsc ¼ 8.66 mA cm_x0002_2, Voc ¼ 0.98 V and FF ¼ 0.54. The high Voc value of the device has been attributed to the deeper HOMO energy level of BDT(CDTRH)2. The overall PCE of the device has been increased up to 6.02% (Jsc ¼ 10.42 mA cm_x0002_2, Voc ¼ 0.94 V FF ¼ 0.62) when the blend was processed with 3% v/v CN/CF solvent. This increase is mainly due to an increase in Jsc and FF, which was linked to the increase in crystallinity and favorable nanomorphology of the active layer improving exciton dissociation and achieving a more balanced charge transport in the device.</div
Selective Organic Contacts for Methyl Ammonium Lead Iodide (MAPI) Perovskite Solar Cells: Influence of Layer Thickness on Carriers Extraction and Carriers Lifetime
We
have fabricated MAPI solar cells using as selective contacts
PEDOT:PSS polymer for holes and PCBM-C70 fullerene derivative for
electrons. The thickness of MAPI, PCBM-C70, and PEDOT:PSS layers has
been varied in order to evaluate the contribution of each layer to
the final device performance. We have measured the devices capacitance
under illumination and the charge carrierâs lifetime using
photoinduced time-resolved techniques. The results show that in this
kind of devices the limiting layer is the PCBM-C70 due to its relative
reduced mobility compared to PEDOT:PSS that makes the control of the
fullerene thickness crucial for device optimization. Moreover, capacitive
measurements show differences for the devices having different PCBM-C70
layer thicknesses in contrast with the measurements on the different
PEDOT:PSS thickness. These give indications about holes and electrons
storage and their distribution
AâpâDâpâA based porphyrin for solution processed small molecule bulk heterojunction solar cells
In this article, we have designed and synthesized a porphyrin with the following molecular architecture A– p–D–p–A in which ethyl rhodanine end capping groups were linked to the core porphyrin donor via an octyl thiophene-ethynylene p bridge denoted as VC117 and used it as an electron donor along with ([6,6]-phenyl C71 butyric acid methyl ester) (PC71BM) as an electron acceptor for the fabrication of solution processed organic solar cells. The solution processed BHJ organic solar cell with an optimized weight ratio of 1 : 1 VC117 : PC71BM in THF (tetrahydrofuran) showed an overall power conversion efficiency (PCE) of 2.95% with short circuit current Jsc ¼ 8.34 mA cm_x0002_2, open circuit voltage Voc ¼ 0.82 V and fill factor FF ¼ 0.43. Nonetheless, when the active layer of the solar cell was processed from a mixture of 4% v/v of pyridine in THF solvent, it achieved a PCE value of 4.46% and further improved up to 5.50% after thermal annealing. This is ascribed to the enhancement of both the Jsc and FF values. The higher value of Jsc is explained by the increased absorption profile of the blend, the higher incident photon to current efficiency (IPCE) response and the better crystallinity of the active layer when processed with solvent additives and thermal annealing while the enhancement of FF is due to the better charge transport capability and the charge collection efficiency of the latter device.</div