Designed and synthesizedde novoANTPABA-PDI nanomaterial as an acceptor in inverted solar cell at ambient atmosphere.

In this work, a novel soluble and air-stable electron acceptor containing perylenediimide moiety named ANTPABA-PDI was designed and synthesized with band gap 1.78eV and that was used as non-fullerene acceptor material. ANTPABA-PDI possess not only good solubility but also much lower LUMO (lowest unoccupied molecular orbital) energy level. Furthermore, its excellent electron acceptor capability also supported by density functional theory calculation which validates the experimental observations. Inverted organic solar cell has been fabricated using ANTPABA-PDI along with P3HT as standard donor material in ambient atmosphere. The device, after characterization in open air, exhibited a power conversion efficiency of 1.70%. This is the first ever PDI based organic solar cell that has been fabricated completely in ambient atmosphere. The characterizations of the device have also been performed in ambient atmosphere. This kind of stable organic material can easily be used in fabricating organic solar cell and therefore it can be used as the best alternative as non-fullerene acceptor materials.

Phenothiazine functionalized fulleropyrrolidines: synthesis, charge transport and applications to organic solar cells.

A series of phenothiazine-C60/70 dyads containing fulleropyrrolidine tethered to C-3 position (C60-PTZ and C70-PTZ) or to the heteroatom N-position via either phenyl (C60-Ph-PTZ and C70-Ph-PTZ) or phenoxyethyl linkers (C60-PhOEt-PTZ and C70-PhOEt-PTZ) of the phenothiazine were synthesized and light-induced electron transfer events were explored. Optimized studies suggested that the highest molecular orbital (HOMO) resides on donor phenothiazine moiety while lowest molecular orbital (LUMO) on the acceptor fulleropyrrolidine moiety of the dyads. Optical and electrochemical properties suggested no electronic communication between the donor and acceptor moieties in the ground state. However, steady-state emission studies in solvents of varied polarity, involving selective excitation of C60/C70, disclosed that the emission intensity of C60/C70 was quenched in the dyads in the increasing order, C60/70-PTZ > C60/70-Ph-PTZ > C60/70-PhOEt-PTZ as a consequence of the donor-acceptor distance resulted due to spacer lengths. Also, the emission quenching is more pronounced in polar solvents such as DMF compared to a non-polar solvent, toluene. With the support of parallel electrochemical studies, the emission quenching is attributed to intramolecular photo-induced electron transfer occurring from PTZ to (C60/C70)* generating a radical ion pair, PTZ+⋅-C60-⋅/PTZ+⋅-C70-⋅. Finally, bulk heterojunction (BHJ) solar cells devices inverted fashion prepared by employing the dyads as acceptors, and PTB7 as donor, suggested that the devices prepared from C70 derivatives i.e., PTB7:C70-PTZ and PTB7:C70-PhOEt-PTZ exhibited better power conversion efficiency of 2.66% and 2.15%, respectively over C60 derivatives i.e., PTB7:C60-PTZ and PTB7:C60-PhOEt-PTZ with the efficiencies of 1.80 and 1.72%, respectively. AFM studies revealed that the poor performance of PTB7:C60-PTZ- and PTB7:C60-PhOEt-PTZ-based devices can be ascribed to the lower solubility of the dyads in 1,2-DCB solvent leading to rough morphology.

Heavy Water Additive in Formamidinium: A Novel Approach to Enhance Perovskite Solar Cell Efficiency.

Heavy water or deuterium oxide (D2 O) comprises deuterium, a hydrogen isotope twice the mass of hydrogen. Contrary to the disadvantages of deuterated perovskites, such as shorter recombination lifetimes and lower/invariant efficiencies, the serendipitous effect of D2 O as a beneficial solvent additive for enhancing the power conversion efficiency (PCE) of triple-A cation (cesium (Cs)/methylammonium (MA)/formaminidium (FA)) perovskite solar cells from ≈19.2% (reference) to 20.8% (using 1 vol% D2 O) with higher stability is reported. Ultrafast optical spectroscopy confirms passivation of trap states, increased carrier recombination lifetimes, and enhanced charge carrier diffusion lengths in the deuterated samples. Fourier transform infrared spectroscopy and solid-state NMR spectroscopy validate the N-H2 group as the preferential isotope exchange site. Furthermore, the NMR results reveal the induced alteration of the FA to MA ratio due to deuteration causes a widespread alteration to several dynamic processes that influence the photophysical properties. First-principles density functional theory calculations reveal a decrease in PbI6 phonon frequencies in the deuterated perovskite lattice. This stabilizes the PbI6 structures and weakens the electron-LO phonon (Fröhlich) coupling, yielding higher electron mobility. Importantly, these findings demonstrate that selective isotope exchange potentially opens new opportunities for tuning perovskite optoelectronic properties.

A fluorene-core-based electron acceptor for fullerene-free BHJ organic solar cells-towards power conversion efficiencies over 10.

A small molecule non-fullerene electron acceptor (SMNFEA), bearing a furan π-spacer and dicyano-n-hexyl rhodanine as flanking groups, was designed and synthesized for organic solar cell applications. Organic photovoltaic devices based on FRdCN2 and PTB7-Th polymer donors exhibited a highly improved efficient power conversion efficiency of 10.7%, which is the highest so far for OSCs fabricated from fluorene-core-based SMNFEAs.

D-π-A-π-D Structured Diketopyrrolopyrrole-Based Electron Donors for Solution-Processed Organic Solar Cells.

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.

A simple fluorene core-based non-fullerene acceptor for high performance organic solar cells.

A small molecule non-fullerene acceptor based on a fluorene core having a furan π-spacer and end capped with rhodanine (FRd2) is developed for solution processable bulk heterojunction organic solar cells (OSCs). The simplistic synthetic protocol reduces several reaction steps and hence production cost. Extended π-conjugation via furan units and the presence of electronegative rhodanine groups result in a power conversion efficiency of 9.4% in OSCs, which is the highest so far among these categories of molecules.

Achieving the highest efficiency using a BODIPY core decorated with dithiafulvalene wings for small molecule based solution-processed organic solar cells.

A novel boron dipyrromethene based dye, coded as BODIPY-DTF, decorated with dithiafulvalene wings has been developed for solar cell application. A very high efficiency of 7.2% has been achieved, which is the highest reported value so far for BODIPY based donors. A remarkable value of about 88.1% of external quantum efficiency has also been observed at 371 nm.

Effectiveness of External Electric Field Treatment of Conjugated Polymers in Bulk-Heterojunction Solar Cells.

External electric field treatment (EFT) on P3HT:PCBM bulk heterojunction (BHJ) devices was recently found to be a viable approach for improving the power conversion efficiencies (PCEs) through modulating the blend nanomorphology. However, its effectiveness over the broad family of polymer-fullerene blends remains unclear. Herein, we investigate the effects of external EFT on various polymer-fullerene blends with distinct morphologies stemming from the difference in molecular structure of the polymers (i.e., semicrystalline vs amorphous) in a bid to establish a clear morphology-function-charge dynamics relationship to the photovoltaic performance. Our findings reveal that EFT promotes self-organization of the semicrystalline thiophene-based conjugated polymers (i.e., P3HT and P3BT) while it was ineffective for the amorphous polymers (i.e., PTB7 and PCPDTBT) even at the maximum applied E-field of 8 kV cm-1. Transient absorption spectroscopy shows an improvement in the initial charge-carrier and polaron formation from delocalized excitons in the E-field treated semicrystalline blends compared to their untreated reference samples. Interfacial trap-assisted monomolecular and trap-free bimolecular recombination at nanosecond-microsecond time scale in the E-field treated P3BT:PC60BM devices are significantly suppressed. Importantly, our findings shed new light and provide guidelines on the effectiveness of utilizing external EFT to enhance the PCEs of a larger family of conjugated polymer-based BHJ OSCs.