Synthesis and optoelectronic properties of amino-functionalized carbazole-based conjugated polymers

Dong

et al. 2015

Adv Funct Materials

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wileyonlinelibrary.comdevices by matching energy levels and optimizing morphologies. [1][2][3][4] Semiconducting π-conjugated polymers made of donor-acceptor (D-A) hybrids are still leading the development, which show facile tuning of band gaps and energy levels by introducing new or different constituent units. [ 5,6 ] However, in comparison to the development of new conjugated building blocks, modifying side chains offers an alternative, perhaps more convenient and cost-effective route to optimize materials. [7][8][9][10][11][12][13][14][15][16][17][18] Modifying side chain constituents is usually done in a framework of an established high-performance backbone with the aim of fi ne tuning the morphology. The selection of side chain substituents, usually alkyl units, needs to balance polymer solubility with the ability for the main chains to self-assemble into ordered units. Polymers with bulky side chains have good solubility in organic solvents for processing, and less bulky side chains provide good interchain packing that ensures charge-carrier transport in solid fi lms. Using advanced structural characterization tools, a number of recent studies have shown the importance of side chain tuning. For example, Beaujuge et al. showed that side chains can infl uence the polymer self-assembly and preferential crystalline orientation; [ 19 ] Cho et al. demonstrated that the solubility, energy level, light absorption, surface tension, and intermolecular packing of the resulting polymers could be changed by altering the functional groups of side chains; [ 20 ] Osaka et al. found that the backbone orientation can be changed by tuning the length between adjacent side chains; [ 21,22 ] McGehee et al. studied the molecular interactions between polymer segments and fullerenes using linear and branched side chains. [ 23 ] Each of these parameters strongly affects the morphology and power conversion effi ciencies (PCEs) of photovoltaic devices. There is no universal guidance to select the chemical constitution of the ideal side chains. From the viewpoint of solubility, longer linear alkyl chains afford comparable solubility to shorter, branched alkyl substituents. [ 9 ] From the molecular ordering viewpoint, linear side chains will promote π-π stacking between the backbones, leading to better charge transport and, usually, higher short circuit currents ( J sc ). [ 10 ] However, strong intermolecular interactions can lead to greater dark currents ( J so ) that reduce the open circuit voltage ( V oc ). [ 14 ] Consequently, there is a delicate balance that needs to be struck to generate conjugated polymers with a suitable mixture of linear and branched side Optimizing Light-Harvesting Polymers via Side Chain EngineeringPeng Liu , Sheng Dong , Feng Liu , * Xiaowen Hu , Liqian Liu , Yaocheng Jin , Shengjian Liu , Xiong Gong , Thomas P. Russell , * Fei Huang , * and Yong Cao A series of conjugated polymers using naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole and benzodithiophene alternating backbone is synthesized to investigate the...

Section: Resultsmentioning

confidence: 99%

Optimizing Light‐Harvesting Polymers via Side Chain Engineering

Dong

et al. 2015

Adv Funct Materials

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“…The conjugated polyelectrolytes were used to improve charge injection from electrodes into organic active layers. [32,33] The BHJ photoactive materials were dissolved in hot o-DCB with stirring overnight before spin-coating on substrate. P1 exhibited a very good film forming capability.…”

Section: Resultsmentioning

confidence: 99%

Polymer Solar Cells Based on the Copolymers of Naphtho[1,2‐c:5,6‐c]bis(1,2,5‐thiadiazole) and Alkoxylphenyl Substituted Benzodithiophene with High Open‐Circuit Voltages

Zhang

et al. 2015

Chin. J. Chem.

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Two novel naphtho [1,2-c:5,6-c]bis(1,2,5-thiadiazole) and alkoxylphenyl substituted benzodithiophene based copolymers were developed as the donor materials for polymer solar cells. The resulting copolymers exhibit broad absorption bands in the range of 500-800 nm in thin films and deep highest occupied molecular orbital energy levels of −5.39 eV and −5.36 eV, respectively. The best device performance was achieved by P1, with an open-circuit voltage of 0.85 V, a short-circuit current density of 8.65 mA•cm −2 , a fill factor of 37.8%, and a power conversion efficiency of 2.78%.

“…However, there are only a few reports of CPEs eLbL film use for PSCs, and those devices typically exhibited relatively poor device performance . In fact, CPEs are one of the most effective cathode interlayer materials . However, due to their relatively low electron mobility, one drawback of CPEs is that they must be kept extremely thin (≈5 nm) to achieve optimal device performance, which is not compatible with the roll‐to‐roll coating process.…”

Section: Photovoltaic Performance Of Ptb7‐th/pc71bm Based Inverted Psmentioning

confidence: 99%

High‐Performance Polymer Solar Cells with Electrostatic Layer‐by‐Layer Self‐Assembled Conjugated Polyelectrolytes as the Cathode Interlayer

Zhang

et al. 2015

Advanced Materials

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115

An easy and efficient approach to achieve a large-area cathode interlayer with controlled film composition, uniformity, and thickness under a nanometer scale is reported by using an electrostatic layer-by-layer (eLbL) self-assembly process. The eLbL films provide a new means for preparing efficient interlayers for polymer solar cells (PSCs) and also represent a potential candidate for use in high-performance large-area PSC modules in the future.