No abstract

The optical, electrical and mechanical properties of single-walled carbon nanotubes (SWNTs) are largely determined by their structures, and bulk availability of uniform materials is vital for extending their technological applications. Since they were first prepared, much effort has been directed toward selective synthesis and separation of SWNTs with specific structures. As-prepared samples of chiral SWNTs contain equal amounts of left- and right-handed helical structures, but little attention has been paid to the separation of these non-superimposable mirror image forms, known as optical isomers. Here, we show that optically active SWNT samples can be obtained by preferentially extracting either right- or left-handed SWNTs from a commercial sample. Chiral 'gable-type' diporphyrin molecules bind with different affinities to the left- and right-handed helical nanotube isomers to form complexes with unequal stabilities that can be readily separated. Significantly, the diporphyrins can be liberated from the complexes afterwards, to provide optically enriched SWNTs.

We designed and synthesized the DPPEZnP-TEH molecule, with a porphyrin ring linked to two diketopyrrolopyrrole units by ethynylene bridges. The resulting material exhibits a very low energy band gap of 1.37 eV and a broad light absorption to 907 nm. An open-circuit voltage of 0.78 V was obtained in bulk heterojunction (BHJ) organic solar cells, showing a low energy loss of only 0.59 eV, which is the first report that small molecule solar cells show energy losses <0.6 eV. The optimized solar cells show remarkable external quantum efficiency, short circuit current, and power conversion efficiency up to 65%, 16.76 mA/cm(2), and 8.08%, respectively, which are the best values for BHJ solar cells with very low energy losses. Additionally, the morphology of DPPEZnP-TEH neat and blend films with PC61BM was studied thoroughly by grazing incidence X-ray diffraction, resonant soft X-ray scattering, and transmission electron microscopy under different fabrication conditions.

mobility. [18] However, P-OSCs have a drawback in batch-to-batch reproducibility of donor polymers, which potentially limits the mass deployment of OSCs. [19] Compared to P-OSCs, small-molecule based OSCs (SM-OSCs) are more attractive in commercialization because of well-defined molecular structures, [20][21][22] simpler synthesis and purification, [23][24][25] and low batch-to-batch variations. [26][27][28][29] With the SM donors developed, the state-of-the-art SM-OSCs show similar PCEs as those obtained for P-OSCs (over 11%) using fullerene derivative, PCBM, as the electron acceptor. [19,[30][31][32][33] However, when the NFSM acceptors were used in nonfullerene-based small molecule organic solar cells (NFSM-OSCs) their PCE can only reach slightly over 10% [34][35][36][37] which is much lower than those obtained for nonfullerene polymer solar cells (NFP-OSCs) with usually PCE over 13%. [38,39] The progress of NFSM-OSCs is strongly lagged behind their polymer counterparts.The PCE of an OSC is determined by three parameters, opencircuit voltage (V oc ), short-circuit current density (J sc ), and fill factor (FF). The main reason for the low PCE in NFSM-OSCs is due to their relative low J sc and FF. [40,41] As shown in Table S1 (Supporting Information), all of the efficient NFP-OSCs with PCE over 14% show high J sc (>20 mA cm −2 ) and high FF In this paper, two near-infrared absorbing molecules are successfully incorporated into nonfullerene-based small-molecule organic solar cells (NFSM-OSCs) to achieve a very high power conversion efficiency (PCE) of 12.08%. This is achieved by tuning the sequentially evolved crystalline morphology through combined solvent additive and solvent vapor annealing, which mainly work on ZnP-TBO and 6TIC, respectively. It not only helps improve the crystallinity of the ZnP-TBO and 6TIC blend, but also forms multilength scale morphology to enhance charge mobility and charge extraction. Moreover, it simultaneously reduces the nongeminate recombination by effective charge delocalization. The resultant device performance shows remarkably enhanced fill factor and J sc . These result in a very respectable PCE, which is the highest among all NFSM-OSCs and all small-molecule binary solar cells reported so far.