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Herein reported is the impact of the functionalization of four different semiconducting polymer structures by a linear siloxane‐terminated side‐chains. The latter is tetrasiloxane (Si4) or trisiloxane (Si3) chains, substituted at their extremity to a pentylene linker. The polymer structure is based on 5,6‐difluorobenzothiadiazole comonomer (PF2), a diketopyrrolopyrrole unit (PDPP‐TT), a naphtalediimide unit (PNDI‐T2), and a poly[bis(thiophen‐2‐yl)thieno[3,2,b]thiophene (PBTTT). The properties of these siloxane‐functionalized polymers are scrutinized and compared with the ones of their alkyl‐substituted polymer analogues. The impact of the alkyl‐to‐siloxane chain substitution clearly depends on the molecular section of the side chains. When a branched 2‐octyldodecyl chain (C20) is replaced by a Si4 chain of same molecular section, the greatest impact is the strong increase of the π‐stacking overlap of the polymer backbones. This effect leads to a significative enhancement of the charge mobility values of the polymers. As in‐plane and out‐of‐plane mobility are increased simultaneously, this π‐overlap enhancement effect happens to be preponderant over the polymer orientation variations. When a linear tetradecyl chain (C14) is replaced by a linear Si3 chain of twice larger molecular section, the polymer structure is profoundly affected. While PBTTT‐C14 is crystalline and purely edge‐on, PBTTT‐Si3 is mesomorphic and shows a mixed face‐on/edge‐on orientation. [ABSTRACT FROM AUTHOR]

Efficient ternary organic photovoltaics (OPVs) are fabricated with two polymer materials PF2 and J71 as donors and Y6 as the acceptor. The PF2 and J71 based binary OPVs exhibit 10.26% and 9.56% power conversion efficiency (PCE), respectively. Even with similar highest occupied molecular orbital (HOMO) energy levels of PF2 and J71, the J71 based binary OPVs show a relatively high open circuit voltage (VOC) of 0.86 V compared with 0.71 V for PF2 based binary OPVs. The VOCs of ternary OPVs monotonously increased with the increase of J71 content in donors, which should be mainly ascribed to the reduced energy loss according to the VOCs of two binary OPVs and the HOMO energy levels of two donors. The short circuit current density (JSC) and fill factor (FF) of ternary OPVs can also be simultaneously enhanced with the J71 content up to 30 wt% in donors, leading to 12.12% PCE of the optimized ternary OPVs with a JSC of 24.97 mA cm−2, a FF of 64.70% and a VOC of 0.75 V. Reducing energy loss by the ternary strategy is rarely reported in the literature, which should also be an efficient method to realize performance improvement of OPVs. [ABSTRACT FROM AUTHOR]

Direct Heteroarylation Polymerization (DHAP) is becoming a valuable alternative to classical polymerization methods being used to synthesize π-conjugated polymers for organic electronics applications. In previous work, we showed that theoretical calculations on activation energy (Ea) of the C-H bonds were helpful to rationalize and predict the selectivity of the DHAP. For readers' convenience, we have gathered in this work all our previous theoretical calculations on Ea and performed new ones. Those theoretical calculations cover now most of the widely utilized electron-rich and electron-poor moieties studied in organic electronics like dithienyl-diketopyrrolopyrrole (DT-DPP) derivatives. Theoretical calculations reported herein show strong modulation of the Ea of C-H bond on DT-DPP when a bromine atom or strong electron withdrawing groups (such as fluorine or nitrile) are added to the thienyl moiety. Based on those theoretical calculations, new cyanated dithienyl-diketopyrrolopyrrole (CNDT-DPP) monomers and copolymers were prepared by DHAP and their electro-optical properties were compared with their non-fluorinated and fluorinated analogues. [ABSTRACT FROM AUTHOR]

The recently reported high power conversion efficiencies achieved in fluorinated polymer:fullerene solar cells have been accounted for by the presence of face-on oriented polymer backbones that enable charge transport towards the collecting electrodes. In this work, we demonstrate that, in contrast to the results of a number of reports, the face-on polymer orientation is due to the bulky side chains, rather than to aggregation in solution. This conclusion is supported by a comparative study of polymers having similar conjugated backbones but different number of fluorine atoms and different number and type of alkyl side chains. While the latter are primarily introduced to tune polymer solubility, the present in-depth thin-film morphology investigation shows that increasing the chain bulkiness favors formation of crystalline lamellae with face-on oriented backbones, independently of the degree of fluorination. By contrast, introduction of fluorine atoms is found to substantially enhance the π-stacking interactions that remain invariably strong upon blending of the polymer with fullerene. Our results demonstrate that, for the polymer family under investigation, fluorination and functionalization by bulky alkyl side chains are both needed for reaching power conversion efficiencies above 10%. [ABSTRACT FROM AUTHOR]

Solution-processed bulk heterojunction solar cells have experienced a remarkable acceleration in performances in the last two decades, reaching power conversion efficiencies above 10%. This impressive progress is the outcome of a simultaneous development of more advanced device architectures and of optimized semiconducting polymers. Several chemical approaches have been developed to fine-tune the optoelectronics and structural polymer parameters required to reach high efficiencies. Fluorination of the conjugated polymer backbone has appeared recently to be an especially promising approach for the development of efficient semiconducting polymers. As a matter of fact, most currently best-performing semiconducting polymers are using fluorine atoms in their conjugated backbone. In this review, we attempt to give an up-to-date overview of the latest results achieved on fluorinated polymers for solar cells and to highlight general polymer properties' evolution trends related to the fluorination of their conjugated backbone. [ABSTRACT FROM AUTHOR]

Herein, a high‐efficiency host material for single‐layer phosphorescent organic light‐emitting diodes (SL‐PhOLEDs) is reported. This host material is synthesized via an efficient approach and is constructed on the association of an electron‐rich phenylacridine unit connected by a spiro carbon atom to an electron‐deficient 2,7‐bis(diphenylphosphineoxide)‐fluorene. In addition to a high ET value and adequate highest occupied molecular orbital/lowest unoccupied molecular orbital energy levels, the key point in this molecular design is the suitable balance between hole and electron mobilities, which leads to a high‐performance blue SL‐PhOLED with an external quantum efficiency of 17.6% (current efficiency = 37.8 cd A−1 and power efficiency = 37.1 lm W−1) and a low Von of 2.5 V. This performance shows that the molecular design of the present host fulfills the criteria required for high‐efficiency SL‐PhOLEDs. The present performance is one of the highest reported to date for blue SL‐PhOLEDs and more importantly shows the potential of such a molecular design to reach very high‐performance single‐layer devices. [ABSTRACT FROM AUTHOR]

Several bottlenecks need to be passed to reach market readiness for organic photovoltaic modules. To avoid scarce and costly materials such as indium is an important technological issue. To be able to process the active layer from solutions prepared from non‐halogenated solvents and harmless additives is also a crucial step. Herein, a fluorinated polymer is used as an electron‐donor material and PC71BM as an electron‐accepting material in a bulk‐heterojunction configuration, to demonstrate that indium‐tin‐oxide (ITO)‐free modules with an active area greater than 60 cm2 and processed from non‐halogenated solvents and harmless additives can reach a high power conversion efficiency of above 6%. [ABSTRACT FROM AUTHOR]

A series of donor‐acceptor (D‐A) π‐conjugated polymers, based on indacenodithienothiophene (IDTT) as an electron‐donating unit and quinoxaline as an electron‐deficient moiety, are synthesized via a Pd‐catalyzed Stille cross‐coupling polymerization. Molecular characteristics, photovoltaic parameters, and optoelectronic properties are examined through structural differences corresponding to thienyl versus phenyl side group substitutions on the IDTT and the non‐fluorinated versus the monofluoro quinoxaline derivatives. One of the most important outcome is that the power conversion efficiency (PCE) in the studied polymers is more device architecture dependent (conventional vs inverted) rather than chemical structure dependent. From single junction solar cells based on bulk heterojunction polymer:[6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) systems as the active layer, a maximum PCE of 5.33% has been achieved from the polymer containing the thienyl substituent on the IDTT and one fluorine atom on the quinoxaline. This demonstrates that finding the optimum molecular weight of ThIDTT‐QF or introducing the monofluoro‐quinoxaline in a regioregular motif in the polymer backbone significantly higher PCE can be expected versus the fully optimized high performance PhIDTT‐Q conjugated polymer. A correlation between polymer chemical structure—optoelectronic properties—organic solar cell performances has been performed in a series of donor‐acceptor (D‐A) π‐conjugated polymers, based on indacenodithienothiophene as an electron‐donating unit and quinoxaline as an electron‐deficient moiety. [ABSTRACT FROM AUTHOR]

In this work, a new n-type polymer based on a thiazole-diketopyrrolopyrrole unit has been synthesized through direct (hetero)arylation polycondensation. The molar mass has been optimized by systematic variation of the the monomer concentration. Optical and electrochemical properties have been studied. They clearly suggested that this polymer possess a high electron affinity together with a very interesting absorption band, making it a good non-fullerene acceptor candidate. As a consequence, its charge transport and photovoltaic properties in a blend with the usual P3HT electron-donating polymer have been investigated. [ABSTRACT FROM AUTHOR]