Role of Energy Transfer in Conversion of Light to Electric Energy

The role of nonradiative inductive-resonance energy transfer between molecules of Coumarine-7 and rhodamine dyes in the conversion of light into electric energy is studied. It is ascertained that the co-sensitization of a TiO₂ solar cell by donor and acceptor molecules leads to an increase of the efficiency of conversion of light to energy. The measurements show that it is due to a widening of the photosensitivity of a cell into the blue region of the spectrum. The increase of the total energy absorbed promotes increasing the number of generated charge carriers at the interface of TiO₂ and dyes.     

Optical excitations in C60/PPV composites

Charge transfer (CT) and subsequent exciton dissociation are essential for organic donor/acceptor solar cells. We analyze these processes by calculating optical intrachain and CT excitations in a model donor/acceptor system. It is found that the increased electron affinity of low-gap polymers may seriously inhibit the CT efficiency. The consequences for exciton dissociation via tunneling are computed.     

Solution-processed small-molecule organic solar cells based on diketopyrrolopyrrole and perlyene derivatives with coplanar structures

ABSTRACT

A series of small-molecules (SMs) based on coplanar perylene unit coupled with diketopyrrolopyrrole chromophoric core exhibit broad absorption in the range of 500–800 nm and low bandgap energise of 1.6–1.7 eV. The power conversion efficiency approximately reach at 0.4% under 1.5 G illumination is achieved for organic solar cells based on a small-molecule bulk heterojunction system consisting of SMs as a donor and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) as an acceptor.     

Syntheses and Photovoltaic Properties of Octyl Cyanoacetate Terminated Small Molecules Based on Benzo[1,2-b:4,5-b’]dithiophene for OPVs

There have been tremendous efforts to synthesize photoactive materials that are consisted of both donor and acceptor components together to increase the power conversion efficiency (PCE) of organic photovoltaic cells (OPVs). In order to improve the performance of the OPVs, in this study, we proposed new A-D-A (Acceptor-Donor-Acceptor) type small molecular donors based on the donor unit of benzo[1,2-b:4.5-b’]dithiophene (BDT) with an acceptor unit of alkyl cyanoacetate. We characterized prepared photoactive materials using ¹H NMR spectroscopy, DSC, CV (cyclic voltammetry), and UV/Vis spectroscopy. We also investigated the relationship between PCEs of OPVs and the active materials with variation of substituted methyl groups. The OPVs based on synthesized photoactive materials with different methyl substitutions showed different PCEs. Our results indicate that synthesized small molecular donor materials are promising donor materials for performance OPVs     

Structural investigation of model compounds for an acceptor component of a new type of charge-transfer complexes based on viologen analogues. Characteristic features of the molecular and supramolecular structures

The crystal and molecular structures of six perchlorates (viologen analogues) are studied. These compounds serve as models of the acceptor component of new charge-transfer complexes containing bis(18-crown-6)stilbene as the donor. The polycyclic aromatic system of divalent cations is demonstrated to be virtually planar. In all cations, the side chains at the nitrogen atoms are oriented in opposite directions almost perpendicular to the plane of the cyclic system. This orientation of the spacers of these carbocations is indicative of their preorganization for the formation of 1: 2 charge-transfer complexes. Analysis of the crystal packings provides evidence that two positive charges on the conjugated systems of the organic cations and the perchlorate anions play a destructive role in the formation of stacking motifs. An increase in the size of the conjugated system and the involvement of an aromatic solvent molecule as an additional building block in a supramolecular system are favorable for the formation of a stacking supramolecular architecture.     

Enhanced Chemical Stability of ZnO Electrode for Dye-Sensitized Solar Cells with Ru Dyes Containing Limited Acidic Anchor Group

Two new Ruthenium-based dyes with carbazole groups (Ru-DiCz) or triphenyl amine groups (Ru-DiTPA) as donor moieties of a ligand were studied for ZnO-based dye-sensitized solar cells. Strong electron-rich donor moieties in both dyes induced a high molar extinction coefficient, thereby enhancing the overall power conversion efficiency through high J_SC value. With limited acidic carboxyl anchor groups on the new Ru-dyes, the solar cells showed superior stability without aggregation of ZnO nanoparticles for a long-term immersion compared with a reference N3 sensitizer.     

Organic dyes incorporating 9,10-dihydrophenanthrene moiety for dye-sensitized solar cells

Abstract

A series of new dipolar organic dyes containing 9,10-dihydrophenanthrene has been synthesized as sensitizers for the application in dye-sensitized solar cells. These new materials containing less rigid π–linker as sensitizers exhibit good performance with conversion efficiencies ranging from 1.58% to 6.21% reaching 11?～?83% of the ruthenium dye N719-based cell under the same condition.     

Effect of fused thiazolothiazole on the photovoltaic performance of fluorene-thiazole-based conjugated polymers

In this work, we utilized two fluorene-based polymers (F8TBTT and F8TTZT) as donor materials in organic photovoltaic cells (OPVs) and compared their performance to explain the effect of substituting fused thiazolothiazole for the bithiazole moiety. The OPV device based on F8TTZT showed a power conversion efficiency of 0.24%, which is three times higher than that of F8TBTT (0.07%) under the same conditions. The better performance can be explained by the increased planarity and enhanced intermolecular charge transport.     

Synthesis and Characterization of 5′-Hexyl-2,2′-bithiophene Based on Organic Dyes for Dye-Sensitized Solar Cell Applications

A series of new organic dyes, 2-(2,6-bis((E)-2-(5′-hexyl-2,2′-bithiophen-5-yl)vinyl)-pyran-4-ylidene)-2-cyanoacetic acid (OD-1) and 2,2′-(2-((E)-2-(5′-hexyl-2,2′-bithiophen-5-yl)vinyl)-1H-indene-1,3(2H)-diylidene)bis(2-cyanoacetic acid) (OD-2), were synthesized as a sensitizers for the application of dye-sensitized solar cells (DSSCs). The introduction of the 5′-hexyl-2,2′-bithiophene units as an electron donor group and 2,6-dimethyl-pyran-4-one or 1,3-indandione as a π-spacers units increased the conjugation length of the sensitizers and thus improved their molar absorption coefficient and light harvesting efficiency.     

Wide band-gap organic molecules containing benzodithiophene and difluoroquinoxaline derivatives for solar cell applications

Abstract

Two new semiconducting organic small molecules, namely BDTQ-BDT(EH) and BDTQ-BDT(OC), were prepared by attaching electron accepting 2,3-didodecyl-6,7-difluoro-5,8-di(thiophen-2-yl)quinoxaline (DTQ) unit on 2,6-position of electron donating 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene (BDT(EH)) and 4,8-bis(octyloxy)benzo[1,2-b:4,5-b']dithiophene (BDT(OC)) units. Molecule BDTQ-BDT(EH) showed higher thermal stability (5% weight loss temperature, T_d “349 ^оC), slightly lower band-gap (E_g “2.10?eV) and deeper highest occupied molecular orbital energy level (HOMO “–5.36?eV) level compared to those (T_d “336 ^оC, E_g “2.11?eV, and HOMO “–5.30?eV, respectively.) of the molecule BDTQ-BDT(OC). The organic solar cells (OSCs) made with the synthesized molecules as an electron donor and [6,6]-phenyl C₇₁ butyric acid methyl ester (PC₇₀BM) as an electron acceptor gave a maximum power conversion efficiency (PCE) of 1.20% and 0.83%, respectively, for BDTQ-BDT(EH) and BDTQ-BDT(OC). This study confirmed that the substituents attached on the 4,8-position of BDT unit greatly alter the properties of the resulting molecules.     

Two-photon sensitive photolabile protecting groups: From molecular engineering to nanostructuration

ABSTRACT

General molecular engineering rules for the optimization of two-photon sensitive cages are presented and examples for nitrobenzyl, indole and nitrophenethyl platforms are highlighted. The efficiency of electron donor and acceptor groups in dipolar structures and the length of the conjugated system in the photolabile protecting group on two-photon uncaging efficiency will be discussed, as well as the emergence of symmetrical platform based on bis-electron donor or on quadrupolar architectures. We will then present our first results on the nano-structuration of donor-acceptor systems based on nitrophenetyl platform using diethyleneglycol or pentaerythritol cores.     

Molecular Cooperation in Photo-Induced Electron Transfer in Monolayer Assemblies

Quenching of fluorescence due to electron transfer is observed in monolayer assemblies when electron donor D and electron acceptor A are either at the same interface or separated by one spacer monolayer. When the donor and acceptor monolayers are separated by two or more fatty acid interlayers no fluorescence quenching is detected.     

Induced SA phases in binary systems with EDA complexing

The phase diagrams of 13 binary systems are presented in which electron donor-acceptor (EDA) complexing is clearly detectable. In all binary systems studied the same electron donor compound was used whereas the electron acceptor compounds were members of two homologous series. It was found that the induction of smectic A phases increases with increasing length of the alkyl chain of the acceptor compound and with increasing stability of the complexes.     

Polymorphism of Supramolecular Charge-Transfer Complex Composed of 10,10′-dihydroxy-9,9′-biphenanthryl and p-benzoquinone

Charge-transfer (CT) complexes were prepared using racemic (rac)-10,10′-dihydroxy-9,9′-biphenanthryl, which has a large and highly π-conjugated phenanthrene ring, as the electron donor and p-benzoquinone as the electron acceptor. This CT system showed a polymorphism.     

Efficiency boost significantly of ternary organic solar cells by doping low bandgap polymer

Ternary blends composed of two donor absorbers and a complementary absorbing material provide an opportunity to enhance the short-circuit current and thus improved the power conversion efficiency (PCE) of polymer solar cells (PSCs). The used of PBT-T-DPP as the complementary electron donor in poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyricacid methyl ester (PC₆₁BM) blend to construct the ternary PSCs. The PCE of the optimized ternary blend PSCs (with 5 wt% PBT-T-DPP) reached 3.65%, which was 15.51% higher than that of the PSCs with binary blends of P3HT:PC₆₁BM. The ternary blend with 5 wt% PBT-T-DPP exhibited well-developed morphology while the blend with 15 wt% PBT-T-DPP showed phase separation with large-sized domains. Improved photovoltaic performance of ternary PSCs was mainly due to complementary absorption of two donors as well as facilitating charge separation and transport while suppressing charge recombination through a combination of cascade energy levels and optimized device morphology.     

Electrical properties of n-Type GaN

The electron mobility in GaN is calculated as function of the carrier and impurity concentrations. From a comparison of the theoretically calculated mobilities with electrical parameters measured experimentally it follows that native donor and acceptor concentrations of the same order of magnitude are present in undoped GaN.     

Triarylamine-Functionalized Ru Dyes with Different Conjugation Lengths for Highly Efficient Dye Sensitized Solar Cells

Triarylamine-functionalized ruthenium (Ru) complexes with different conjugation linkage lengths are synthesized and applied to dye-sensitized solar cells (DSSCs). These triarylamine-functionalized Ru complexes show appreciably high extinction coefficients. DSSCs based on the new dye show higher power conversion efficiency than standard N3 dyes under same conditions. Among others, Ru-TP3 dye that has the longest conjugation length shows the highest efficiency of 3.7% under simulated 1 sun illumination (AM 1.5).     

Synthesis of flower‐like zinc oxide and polyaniline with worm‐like morphology and their applications in hybrid solar cells

ZnO with a “flower‐like” morphology was synthesized using a simple microwave assisted hydrothermal method and used as an acceptor material in hybrid solar cells. X‐Ray diffraction and Raman Spectroscopy confirmed the formation of a highly crystalline wurtzite ZnO structure. A highly crystalline and conductive polyaniline with “worm‐like” morphology was synthesized by chemical polymerization of aniline using KH(IO₃)₂ as an oxidant and was used as a donor material for solar cells. The morphology was probed by using scanning and transmission electron microscopy. Polyaniline with worm‐like morphology had a diameter of 160 nm and about 2 µm long. Solar cell device fabricated from PANI/ZnO active bilayer demonstrated a fill factor of about 22.8%. Upon blending PANI with ZnO the fill factor was improved to 25.6% and efficiency by almost 100 fold when PANI:ZnO 1:1 composite was used as an bulk heterogeneous active layer. The fill factor was further improved to 26.4% when device architecture was changed to diffused bilayer. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electron‐phonon short‐range interactions mobility and p‐ to n‐type conversion in TlGaS2 crystals

The conductivity type conversion from p ‐ to n ‐type at a critical temperature of 315 K in TlGaS₂ crystals is observed through the Hall effect measurements in the temperature range of 200–350 K. The analysis of the temperature‐dependent electrical resistivity, Hall coefficient and carrier concentration data reveals the extrinsic type of conduction with donor impurity levels that behave as acceptor levels when are empty. The data analysis allowed the calculation of hole and electron effective masses of 0.36m ₀ and 0.23m ₀, respectively. In addition, the temperature‐dependent Hall mobility is found to decrease with temperature following a logarithmic slope of ∼1.6. The Hall mobility in the n ‐region is limited by the electron‐phonon short‐range interactions scattering with an electron‐phonon coupling constant of 0.21. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

钙钛矿太阳能电池中电子传输层现状研究

有机-无机杂化钙钛矿型太阳能电池(简称钙钛矿太阳能电池)的最高光电转换效率已经达到25.5%,是最有希望取代硅基太阳能电池并实现广泛应用的太阳能电池之一。作为钙钛矿太阳能电池的基本组成部分,电子传输层对电池的性能起着至关重要的作用。本文阐述了钙钛矿太阳能电池中电子传输层的种类、尺寸以及界面修饰等对器件性能的影响,为继续提升钙钛矿太阳能电池性能提供参考。