In order to attain high performance in single-component organic solar cells (SCOSCs), it requires the designing of light-harvesting structures that can absorb light across a wide range from visible to near-infrared (NIR) wavelengths. In this investigation, two novel dyad materials, denoted as SPS-BF-Full and SPS-BT-Full are designed and synthesized, consisting of covalently linked benzofuran (BF) and benzothiophene (BT) functionalized thiophene–diketopyrrolopyrrole (TDPP) as donor and N-methyl fullero[60]pyrrolidine as the acceptor, respectively. The incorporation of a phenyl bridge between TDPP and fullero[60]pyrrolidine enhances light absorption in SPS-BF-Full and SPS-BT-Full, resulting to a high short-circuit density (JSC). Consequently, the SCOSCs utilizing SPS-BT-Full and SPS-BF-Full attained overall power conversion efficiency (PCE) of 6.28 and 7.35%, respectively. The high photovoltaic performance of OSCs utilizing SPS-BF-Full is mainly attributed to its higher external quantum efficiency and balanced hole and electron mobility (μe/μh = 1.39), along with imporved charge carrier extraction, revealing more effective charge transport in comparison to SPS-BT-Full counterparts.

Metal doping offers a potent strategy for enhancing the optical properties and stability of CsPbCl3 (CPC) perovskites. While Mn doping has drawn attention to its unique attributes, it has failed to achieve the benchmarks set by CsPbBr3 and CsPbI3. To bridge this gap, a codoping approach involving earth-abundant and cost-effective FeCl2 has been explored in this study. PL emission peak intensity increased after codoping with various FeCl2 concentrations in Mn-doped CPC (Mn-CPC) nanocrystals. Fe2+ effectively enhances the Mn doping efficiency in CPC across 0.1-0.3 mmol concentrations by replacing some Pb2+ sites. The resultant Fe-codoped Mn-CPC nanocrystals display orange emission in hexane at 594-606 nm, boasting photoluminescence quantum yields up to 22-27%. Notably, codoped nanocrystals exhibit better photostability under ambient conditions and UV-light irradiation than Mn-CPC. The improved photoresponse characteristics induced by Fe2+ codoping highlight the potential of these nanocrystals for integration into UV-visible photodetectors and other optoelectronic devices. The electrochemical property of Fe ion-codoped Mn-CPC PNCs showed better photocurrent density results than Mn-CPC.

The metal doping process not only enhances the intrinsic properties of semiconducting perovskite nanocrystals (PNCs), including optoelectronic, magnetic, and electrochemical properties, but also significantly improves their photophysical performance. For instance, Mn doping can enhance the photophysical properties of CsPbCl3PNCs to some extent. In addition to doping, surface passivation is a promising strategy to further improve the photophysical properties and stability of these materials. In this study, we demonstrate that the surface defect states of the Mn-doped CsPbCl3PNCs can be effectively reduced through postsynthesis surface passivation with mucic acid at room temperature, resulting in enhanced photophysical properties and stability. The XRD patterns confirmed the successful doping of Mn into the CsPbCl3lattice. FTIR and XPS measurements verified the successful mucic acid passivation. Notably, the mucic acid-treated Mn–CsPbCl3PNCs exhibited a photoluminescence quantum yield of 55–57%, compared to just 18% for unpassivated Mn–CsPbCl3. The photostability test confirms that passivated PNCs are more stable than those without passivation. The Mn-CPC-MA-3 PNCs showed significantly improved current stability and intensity under visible light illumination with a higher photocurrent density of ∼0.01 μA/cm2versus −0.029 μA/cm2for Mn-CPC PNCs.

The development of high-performance, fully non-fused ring electron acceptors (NFREAs) for organic solar cells (OSCs) is often hindered by multistep synthesis, use of hazardous reagents, and high synthetic complexity (SC), ultimately limiting their figure-of-merit (FOM). In this study, we report three simple and cost-effective NFREAs, SN-1, SN-2, and SN-3, featuring a dialkoxybenzene central core and hexyldicyanorhodanine terminal acceptor groups linked via distinct π-bridging units: furan, thiophene, and ethylenedioxythiophene (EDOT), respectively. These NFREAs were synthesized in just four steps using a direct C–H arylation reaction, without any hazardous reagents, with very high overall yields of up to 49%. To enhance the molecular planarity and charge transport, an intramolecular noncovalent interaction strategy was employed to restrict the C–C bond rotation between the π-conjugated units. Notably, SN-3 exhibited multiple O···S and O···H interactions between core and end groups, effectively rigidifying the backbone and promoting J-aggregation. As a result, PM-6:SN-3-based OSCs achieved a power conversion efficiency (PCE) of 11.56%, a high FOM of 67.09, and a low SC value of 17.26. In comparison, devices based on SN-1 and SN-2 delivered PCEs of 10.26% and 6.97%, respectively. These findings underscore the critical role of noncovalent interactions in conformationally stabilizing simple NFREAs and highlight their potential for high FOM OSCs.

Two novel BODIPY dyes, BOC3 and BC12, were synthesized with variable alkyl chains at terminal amide functional units. BC12, featuring a longer alkyl chain (−C12H25), formed a gel compared to BOC3, which has a shorter alkyl chain (< C->CH2OCH3), due to supra molecular self-assembly in film. Both dyes exhibited absorption peaks around 530 nm in the visible region, with a red shift of about 30 nm in the film state, essential for organic electronic applications. Concentration variation studies revealed π-π stacking/aggregates in the solid state causing red shifts in absorption and emission. BC12 exhibited more significant red shifts in film compared to its solution state due to supra molecular self-assembly. Electronic structure analysis using density functional theories (BMK and O3LYP) showed better correlation with absorption using the O3LYP method. Both dyes displayed quasi-irreversible oxidation and reduction couples with suitable HOMO (5.46 eV) and LUMO (3.32 eV) energy levels for organic electronic applications. Transient photoluminescence studies indicated a longer lifetime for BC12 (5.28 ns) than BOC3 (4.50 ns), suggesting π-π aggregation and supra molecular self-assembly. BC12′s gelation, attributed to its long alkyl chain and two-dimensional motifs of the BODIPY core, forms spherical-shaped nano networks. These findings underscore the potential of molecularly tuned dyes with alkyl chains for nano-sized self-assembly in organic electronic devices. Red shifts were observed due to combination of aggregation, stacking and columnar meso-phase formation in supramolecular assembly. Absorption spectra of dyes in toluene with various concentrations showed the formation of Aggregation/π-π stacking might be due to head to tailing interactions.

We demonstrate that hydrocarbon-based non-aromatic molecules can be used as reducing agents to synthesize gold nanoparticles. By using aromaticity as the driving force, stabilized Au particles of size ∼15 nm with twinned structures can be obtained at room temperature.

Organic solar cells (OSCs) have achieved remarkable progress, with power conversion efficiencies (PCEs) surpassing 19-20%, driven by the development of polymeric electron donors and non-fullerene acceptors (NFAs) in bulk-heterojunction (BHJ) architectures. BHJ OSCs, which rely on physical blending of donor (D) and acceptor (A) materials, face significant challenges in maintaining long-term stability. This instability limits the commercial viability of BHJ OSCs despite advancements in optimizing their morphology and device architecture. Single-component organic solar cells (SCOSCs) have emerged as a promising alternative to address these stability challenges. By covalently linking D and A units into a single molecule these single-material devices combine the advantages of light absorption and charge transport within a unified structure, eliminating complex interfacial layers and mitigating phase-separation issues inherent in BHJ systems. To date, SCOSCs have reached a maximum power conversion efficiency (PCE) of 15%, marking notable progress toward bridging the performance gap with BHJ devices. This review highlights the structural advancements in SCOSCs, with a particular emphasis on molecular dyads, D-A double cable polymers and conjugated block copolymers, and their photovoltaic performance. Furthermore, it discusses potential strategies for future innovations to improve the efficiency and scalability of SCOSCs.

Molecular photoswitches that absorb sunlight and store it in the form of chemical energy are attractive for applications in molecular solar thermal energy storage (MOST) systems. Typically, these systems utilize the absorbed energy to photoisomerize into a metastable form, which acts as an energy reservoir. Diarylethenes featuring aromatic ethene π-linkers have garnered research interest in recent years as a promising class of T-type photoswitches, which undergo photocyclization from an aromatic ring-open form into a less aromatic or non-aromatic ring-closed form. Based on several recent computational and experimental studies, this perspective analyzes the potential of these switches for MOST applications. Specifically, we discuss how they can be made to simultaneously achieve high energy-storage densities, long energy-storage times, and high photocyclization quantum yields by tuning the aromatic character of the ethene π-linker.

We report the synthesis of a functional molecule, a quatertiophene-based surfactant, which can both adsorb at the water/gas interface (surface active molecule) and aggregate through π−π stacking interactions. We assess then the ability of this molecule to create these functionalities at interfaces. This interfacial functional aggregation, characterized here in situ for the first time, is probed thanks to Langmuir trough experiments and spectrometric ellipsometry. These results pave the way to the design of new water based optoelectronic devices.

Utilizing hole-transporting materials (HTMs) to extract and transport holes from perovskite materials to the electrode remains essential in most perovskite solar cell (PSC) architectures. Developing cost-effective and efficient HTMs is essential for advancing PSC technology. We have synthesized a novel HTM, TPA-IDT-TPA, which has an extended fused ring as the core moiety called indacenodithiophene (IDT) and p-methoxy triphenylamine (p-mTPA) as terminal groups. TPA-IDT-TPA exhibits appropriate frontier molecular orbital (FMO) energy levels that match perovskite materials. Density functional theory (DFT) simulations were performed to comprehend the electronic, excited-state, and charge transport properties. The DFT results indicate that the extended π-conjugation, rigidity, and the central core ring of the HTM enhanced the π-π stacking, contributing to efficient charge transport. The PSC constructed with TPA-IDT-TPA achieves a device efficiency of 8.34%, with high values of JSC and VOC, which can be further enhanced through molecular optimization.

We report the design of novel medium bandgap nonfullerene small molecule acceptor NFSMA SPS-TDPP-2CNRh with A2-π-A1-π-A2architecture, with the molecular engineering of this material comprising a strong electron-accepting backbone unit DPP (A1) as the acceptor, which is attached to the dicyanomethylene-3-hexylrhodanine (A2) acceptor via a furan (π-spacer) linker. We systematically studied its structural and optoelectronic properties. The incorporation of dicyanomethylene-3-hexylrhodanine and furan enhance the light absorption and electrochemical properties by extending π-conjugation and is anticipated to improve VOCby decreasing the LUMO level. The long alkyl chain units were responsible for the better solubility and aggregation of the resultant molecule. Binary BHJ-OSCs constructed with polymer P as the donor and SPS-TDPP-2CNRh as the acceptor resulted in a PCE of 11.49% with improved VOC= 0.98 V, JSC= 18.32 mA/cm2, and FF = 0.64 for P:SPS-TDPP-2CNRh organic solar cells. A ternary solar cell device was also made using Y18-DMO and SPS-TDPP-2CNRh as acceptors having complementary absorption profiles and polymer P as the donor, resulting in a PCE of 15.50% with improved JSC= 23.08 mA/cm2, FF = 0.73, and VOC= 0.92 V for the P:SPS-TDPP-2CNRh:Y18-DMO solar cell. The ternary OSCs with SPS-TDPP-2CNRh as the host acceptor in the P:Y18-DMO binary film were shown to have improved PCE values, which is mainly attributed to the effective photoinduced charge transfer through multiple networks and the use of excitons from SPS-TDPP-2CNRh and Y18-DMO. Moreover, in the ternary BHJ active layers, the superior stable charge transport that was observed compared to the binary counterparts may also lead to an increase in the fill factor. These results demonstrate that combining medium bandgap and narrow bandgap NFSMAs with a wide bandgap polymer donor is a successful route to increasing the overall PCE of the OSCs via the ternary BHJ concept.

We have design and synthesized two similar A-π-D-π-A structured V-shaped small molecular non-fullerene acceptors named as BYG3 and BYG4 for BHJ-OSCs applications. The molecular architecture of BYG3 and BYG4 consists of an electron rich carbazole as central core, benzothiadiazole as π-spacer and finally it is end caped with naphthamide unit via ethyne linker. The major difference among BYG3 and BYG4 non-fullerene acceptors is fluorine atom substitution at benzothiadiazole unit and the effects of fluorine atom on its optical, electrochemical and photovoltaic properties were well discussed. The optoelectronic properties and band gap of BYG3 and BYG4 acceptors were well synchronized to small molecule donor SMD. Therefore, all small molecule BHJ-OSCs device were constructed using BYG3 and BYG4 as acceptors and small molecule (SMD) as donor results power conversion efficiency (PCE) of 8.09% and 8.57% with high open circuit voltages (Voc) of 1.12 V and 1.05 V respectively. Also, BYG4 based OSCs devices were displayed high values of short-circuit current density (Jsc) and fil factor (FF) are higher for than that for BYG3, may be related to the more effective exciton dissociation and charge transfer in the SMD:BYG4 active layer than that for SMD:BYG3 counterpart. However, the larger value of Voc for the BYG3 based OSCs than BYG4 counterpart may be related to the up-shifted LUMO energy level of BYG3.

We report the synthesis and characterization of a dithienogermole (DTGe) based small molecule, named Ge-PO-2CN, as a donor material for bulk heterojunction (BHJ) organic solar cells (OSCs) and as a hole transport material (HTM) for dopant-free perovskite solar cells (PSCs). This molecule consists with a high planar and electron rich DTGe core as a central core unit and covalently linked with an electron rich phenoxazine group. Finally, it is end-capped with electron-deficient malononitrile group. This molecule was synthesized by a facile synthetic protocol, without using costly and complicated purification techniques. The Ge-PO-2CN compound has a suitable HOMO level with respect to the valence band of the perovskite absorber and the BHJ OSCs. The BHJ OSC device made with Ge-PO-2CN as the donor and PC71BM as an acceptor results in a power conversion efficiency (PCE) of 5.4%. Subsequently, the PSC with an active area of 1.02 cm2 constructed with dopant-free Ge-PO-2CN as an HTM achieved a PCE of up to 11.63%.

Two small molecules BYG-1 and BYG-2 with fluorene donor and benzothiadiazole acceptor units connected to the terminal naphthamide group via ethyne linker were designed and synthesized. In this work we have discussed the effect of fluorine atoms connected with electron withdrawing benzothiadiazole unit to the fluorene core (BYG-1). In this study, we have fabricated solar cells with small-molecular donor and acceptor materials in the device architecture of bulk-heterojunction, using highly conjugated BYG-1 and BYG-2 as electron acceptors along with an appropriate small molecule donor (SMD). After improving the device architecture of the active layer using a suitable donor-to-acceptor weight ratio with solvent vapour annealing, we achieved power conversion efficiencies of 8.67% and 7.12% for BYG-1 and BYG-2, respectively. The superior photovoltaic performance of the fluorine-substituted BYG-1 can be attributed to its higher crystallinity, more balanced charge transport mobilities and efficient exciton dissociation.

Herein, the synthesis of the novel acceptor–donor–acceptor (A–D–A)-structured small molecule Si-PO-2CN based on dithienosilole (DTS) as building block flanked by electron-rich phenoxazine (POZ) units, which are terminated with dicyanovinylene, is presented. Si-PO-2CN showed unique electrochemical and photophysical properties and has been successfully employed in perovskite solar cells (PSCs) as well as in bulk heterojunction organic solar cells (OSCs). The PSCs fabricated with dopant-free Si-PO-2CN as hole-transport material (HTM) exhibited a power conversion efficiency (PCE) of 14.1 % (active area=1.02 cm2). Additionally, a PCE of 5.6 % has been achieved for OSCs, which employed Si-PO-2CN as p-type donor material when blended with a [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) acceptor. The versatile application of Si-PO-2CN provides a pathway for further implementation of DTS-based building blocks in solar cells for designing new molecules.

Conformational diversity due to different orientations of structural subunits has a complex impact on morphological disorder of organic semiconductors. Here, we isolate the impact of a specific structural change: replacing bithiophene (biTh) units with thieno[3,2-b]thiophene (TT). We compare four molecules with an alternating donor-acceptor structure (D′-A-D-A-D′) composed of a central, electron-rich dithienosilole (DTS) unit flanked by pyridyl-[2,1,3]thiadiazole (PT) or fluorinated benzo[c][1,2,5]thiadiazole (FBT) and end-capped with bithiophene biTh or TT groups. We find that using TT instead of biTh results in an increased degree of order within films cast directly from solution by influencing the self-assembly tendencies of the different molecules. Unlike switching the acceptor subunit, such as FBT for PT, the TT for biTh structural change has little impact on the electronic structure of these molecular semiconductors. Instead, these morphological effects can be understood within the context of the predicted conformational diversity. TT units limit the number of rotational conformations (rotamers) available within this molecular architecture; low rotamer dispersity facilitates self-assembly into ordered domains. As a practical illustration of this greater drive toward self-assembly, we use the TT-containing molecules as donors in bulk heterojunction solar cells with PC70BM. Devices with TT-containing molecules show improved photovoltaic performance compared to their previously characterized biTh analogs (d-DTS(PTTh2)2 and p-DTS(FBTTh2)2) in both as-cast and optimized conditions, with efficiencies up to 6.4% and 8.8% for PT-TT and FBT-TT, respectively. The TT subunit and, more broadly, the strategy of limiting conformational diversity can be readily applied toward the design of solution-processable organic semiconductors with increased as-cast order.

Solution-processable D-π-A-π-D structured two organic small molecules bearing thienyl diketopyrrolopyrrole (TDPP) and furanyl diketopyrrolopyrrole (FDPP) as central acceptor units and cyano on the π-bridge and phenothiazine as the terminal donor units, coded as TDPP-PTCN and FDPP-PTCN, are designed and synthesized. The C-H arylation and Suzuki coupling protocols have been adopted for synthesizing the molecules. Solution-processed organic solar cells (OSCs) were constructed with these molecules as the donors and phenyl-C71-butyric acid methyl ester as the acceptor yielding power conversion efficiencies (PCE) of 4.0% for FDPP-PTCN and 5.2% for TDPP-PTCN, which is the highest PCE reported so far from the small molecular DPP-phenothiazine-based architecture for solution-based OSCs. The effect of heteroatom substitution on thermal stability and optoelectronic and photovoltaic performances is also systematically investigated herein. This work demonstrates that replacement of oxygen with sulfur in these kinds of small molecules remarkably improves the photovoltaic performance of OSCs.

Synthesis and photophysical characterizations of two novel small molecules SQ-BEN-THI and SQ-BEN-FUR with D-A-D molecular structure consisting of squaraine as central unit and benzothiophene and benzofuran as end groups are being reported. Apart from very sharp and intense light absorption by these molecular sensitizers in near-infrared (NIR) wavelength region, their possibility as small molecular organic semiconductor was also explored after fabricating organic field-effect transistors (OFETs). Results obtained from photophysical, electrochemical, and quantum chemical studies were combined to elucidate the structural and optoelectronic properties. Electrical characterization pertaining to the charge-transport properties carried after OFET fabrication exhibited field-effect mobilities of 4.0 × 10-5 and 5.4 × 10-5 cm2/(V s) for SQ-BEN-THI and SQ-BEN-FUR, respectively. After thermal annealing at 130 °C, the field-effect mobility was found to increase for both squaraine dyes. Relatively facile carrier transport in SQ-BEN-FUR compared to that of SQ-BEN-THI could be attributed to relatively higher backbone planarity as indicated from optimized molecular structure obtained after density functional theory calculations. This work may guide for further molecular design and synthesis of novel squaraine dyes for high-performance OFET applications.

With the objective of developing fluorescent switch molecule, we have designed, synthesized and photophysically characterized a novel fluorophore-photochrome dyad molecule comprising Phenothiazine derivative (PTCN, 4) and photochromic spiropyran (SP, 6). We successfully demonstrate that the photochromic behaviours of spiropyran unit regulate the fluorescence behaviours of phenothiazine derivative in terms of change in fluorescence intensity in PTCN-SP(8) dyad in the solution as well as in the solid state by employing steady state spectroscopic techniques. The as prepared PTCN-SP(8) is strongly fluorescent with fluorescent quantum yield more than 10% and regards as fluorescent “on” state. The spiropyran ring of photochrome (SP) opens up forming isomeric conformer, known as marocyanin (MC), upon UV irradiation in the dyad. This photogenerated isomer (MC) acts as an energy acceptor for PTCN fluorophore and energy transfer occurs from PTCN to MC via Förster resonance energy transfer (FRET) mechanism which leads to quench the fluorescence of PTCN and it is assigned to fluorescent “off” state. Subsequent visible light irradiation or thermal stimulation to the dyad is accompanied by ring close isomer SP along with complete reversal of the characteristic fluorescence of the PTCN(4), fluorescent “on” state. As a result, the photoinduced reversible transformations of the photochromic component within the dyad effectively bring “on” and “off” states of the PTCN fluorescence emission. Indeed, the fluorescence of this photoswitchable dyad is modulated for several cycles with excellent fatigue resistance under optical control for both in solution and solid phases. Thus, the choice of PTCN(4) as fluorescent probe in the dyad can ultimately lead to the development of valuable photoswitchable fluorescent probe for device applications.

Herein two conjugated donor molecules, TDPP-POCN and FDPP-POCN, with planar diketopyrrolopyrrole (DPP) as the core building-block acceptor unit and phenoxazine-capped acrylonitriles as arms are designed and synthesized. Solution-processed bulk-heterojunction organic solar cells based on blends of the small-molecule donors and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) exhibit promising photovoltaic device performance with a maximum power conversion efficiency up to 4.8 % for TDPP-POCN and 3.4 % for FDPP-POCN under the illumination of AM1.5G, 100 mW cm–2. To the best of our knowledge, this is the highest efficiency reported so far in DPP–phenoxazine-based systems and among acrylonitrile-bridged donor-π-acceptor-π-donor-structured small-molecule donors for solution-processed small-molecule-based organic solar cells.

A new low band gap small molecule DPP-DTF with a D-π-A-π-D molecular structure composed of a dithiafulvalene (DTF) donor and a diketopyrrolopyrrole (DPP) acceptor was synthesized and tested for organic solar cells. Using the DPP-DTF small molecule as an electron donor, and PC71BM as an acceptor a high power conversion efficiency (PCE) of 4.3% was achieved.

A new low-band gap dyad DPP-Ful, which consists of covalently linked dithiafulvalene-functionalized diketopyrrolopyrrole as donor and fullerene (C60) as the acceptor, has been designed and synthesized. Organic solar cells were successfully constructed using the DPP-Ful dyad as an active layer. This system has a record power-conversion efficiency (PCE) of 2.2 %, which is the highest value when compared to reported single-component organic solar cells.

A new thermoreversible organogel based on diketopyrrolopyrrole dye (DPP-NCO) is reported for the first time and evolved as a new building block for the fabrication of 1D supramolecular assembly. AFM analysis illustrated that its gel state is composed of different sized 1D rods. DPP-NCO gel used as an additive in organic solar cells yields high efficiency of 7.9% owing to better nanophase separation of its active layer.

We report the synthesis and characterization of a new fluorescent dyad SP-DPP-SP(9) via efficient palladium-catalyzed Sonogashira coupling of prop-2-yn-1-yl 3-(3′,3’dimethyl-6-nitrospiro[chromene-2,2′-indolin]-1′-yl)propanoatespiropyran, SP(8), a well known photochromic accepter, with 3,6-bis(5-bromothiophen-2-yl)-2,5-bis((R)-2-ethylhexyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione, DPP(4), a highly fluorescent donor. Under visible light exposure the SP unit is in a closed hydrophobic form, whereas under UV irradiation it converts to a polar, hydrophilic open form named Merocyanine (MC), which is responsible for functioning of photo-switch application. The photochemistry pertaining to fluorescence switch, ‘on/off’ behaviour, of model dyad SP-DPP-SP(9) is experimentally analyzed in solution as well as in solid state in polymer matrices by photoluminescence(PL) and absorption spectroscopy. After absorption of UV light the spiropyran unit of the dyad under goes the rupture of the spiro C-O bond leading to the formation of MC. The absorption band of MC fairly overlaps to the fluorescence of DPP unit resulting quenching of fluorescence via fluorescence resonance energy transfer from exited DPP unit to ground state MC. In contrary, the fluorescence of DPP is fully regained upon transformation of MC to SP by exposure to visible light or thermal stimuli. Hence, the fluorescence intensity of dyad 9 is regulated by reversible conversion among the two states of the photochromic spiropyran units and the fluorescence resonance energy transfer (FRET) between the MC form of SP and the DPP unit. Conversely, these scrutiny of the experiment express that the design of dyad 9 is viable as efficient fluorescent switch molecule in many probable commercial applications, such as, logic gates and photonic and optical communications.

A conjugated D-A copolymer (P) having benzodithiophene donor and benzo[1,2,5]thiadiazole acceptor was employed as a p-type hole transporting material in solid state organic-inorganic hybrid solar cells and compared with the P3HT hole transporting material. In these device we have used organo-lead halide (CH3NH3PbI3) synthesized by us, as light harvester. The power conversion efficiency (PCE) of 6.64% is achieved for the solar cell with P which is higher than that for P3HT (4.24%). The increase in PCE is mainly due to the enhancement in FF and Voc and attributed to higher mobility of hole for conjugated copolymer than P3HT.

We have designed and synthesized two new diketopyrrolopyrrole (DPP) based organic sensitizers (DPPCA and DPPCN) with the dithiafulvalene (DTF) unit as donor and cyanoacrylic acid/malononitrile as acceptor moieties. These dyes showed excellent efficiency of photocatalytic hydrogen production over a Pt-TiO<inf>2</inf> composite via solar-induced water splitting. The sensitizers showed broad absorptions over the wide visible regime (500-800 nm). In DPPCN, the malononitrile moiety led to strong intra-molecular charge transfer, as evidenced by red shifted (∼24 nm) absorption maxima with highly enhanced molar absorptivity (108190 M^-1 cm^-1). The electrochemical characterization of as-prepared sensitizers confirmed the feasible electron injection from the dye to the TiO<inf>2</inf> conduction band (CB) which has been further validated by theoretical studies. In this study, the rate of the photocatalytic activity was found to be dependent on the acceptor part of the dye molecule as DPPCN sensitized Pt-TiO<inf>2</inf> (DNPT) exhibited remarkable (1208 μmol) hydrogen evolution yield in comparison to DPPCA sensitized Pt-TiO<inf>2</inf> (DAPT) (840 μmol). The rigid DPP core made the sensitizers significantly photo-stable as affirmed by their high hydrogen production efficiency over 80 h of prolonged irradiation. As predicted from density functional theory (DFT) calculations, ground state geometry of the dyes was almost planar, facilitating continuous conjugation throughout the molecule. Time-dependent DFT (TD-DFT) calculations were also carried out to make clear the understanding of charge transfer transition of the dye molecules. This journal is

Two novel heteroleptic Ru[3+2+1] sensitizers, 1 and 2, with unsymmetrical bipyridine as ancillary ligand and electron donating 4-methylstyryl group in the anchoring π-extended terpyridyl ligand were synthesized and characterized. DFT studies reveal that the lowest unoccupied molecular orbital (LUMO) is distributed over the terpyridine. The two new sensitizers showed an improvement in the molar extinction coefficient compared to reference standard N749 dye. Among the two new sensitizers, 1 exhibited maximum solar to electric conversion efficiency (η) of 5.19% with short circuit current density of 14.032 mA cm-2, open circuit voltage of 0.520 V and fill factor of 0.712, under Air Mass (AM) 1.5 sunlight, while the reference N749 sensitized solar cell exhibited η-value of 6.44%.

We synthesized two new organic dyes (KNS1 and KNS2) based on the triphenylamine (TPA) core structure. Both of the dyes contain triphenylamine and thiophene moieties as an electron donor and cyanoacrylic acid and rhodanine-3-acetic acid units as electron acceptors. Nanocrystalline TiO<inf>2</inf> based dye-sensitized solar cells (DSSCs) were fabricated using these dyes to investigate the effect of two different anchoring groups on their photovoltaic performance. The DSSCs based on KNS1 and KNS2 showed power conversion efficiency (PCE) of about 2.01% and 2.95%, respectively. The PCE has been significantly improved upto 3.53% and 3.00%, upon addition of chenodeoxycholic acid (CDCA) to the dye solution.