A green chemical method for synthesis of bromine-containing “building blocks” for the production of photovoltaic polymers

Bromine-containing derivatives of aromatic and heteroaromatic compounds are the most important "building blocks" in the assembly of modern Photovoltaic Polymers (PV). While PV is being developed to produce "green" energy, converting sunlight to electricity, the reactions for producing brominated derivatives of building blocks described in the literature are examples of obsolete and environmentally dirty technologies. More environmentally harmful than bromination with molecular bromine [1] can only be bromination by molecular bromine in a concentrated hydrobromic acid medium [2]. Using 1,1'-diphenyl (1), 9H-diphenylcarbazole (2) and thiophene (3) as examples, we successfully tested the bromination of the above objects with a mixture of potassium bromide and bromate in acetic acid as outlined in the diagram

Mapping charge carrier mobility at nanoscale

This work was supported by Federal Target Program of MES of Russian Federation, contract 14.575.21.0149 (RFMEFI57517X0149)

Nanoscale mobility mapping in semiconducting polymer films

This work was supported by grant No 19-12-00066 of the Russian Science Foundation.Local electrical properties of thin films of the polymer PTB7 are studied by conductive atomic force microscopy (C-AFM). Non-uniform nanoscale current distribution in the neat PTB7 film is revealed and connected with the existence of ordered PTB7 crystallites. The shape of local I-V curves is explained by the presence of space charge limited current. We modify an existing semi-empirical model for estimation of the nanoscale hole mobility from our experimental C-AFM measurements. The procedure of nanoscale charge mobility estimation was described and applied to the PTB7 films. The calculated average C-AFM hole mobility is in good agreement with macroscopic values reported for this material. Mapping of nanoscale hole mobility was achieved using the described procedure. Local mobility values, influenced by nanoscale structure, vary more than two times in value and have a root-mean-square value 0.22 × 10−8 m2/(Vs), which is almost 20% from average hole mobility.PostprintPeer reviewe

Mapping hole mobility in PTB7 films at nanoscale

Funding: Federal Target Program of MES of Russian Federation, contract 14.575.21.0149 (RFMEFI57517X0149).The nanoscale hole mobility in organic semiconducting polymer PTB7 is quantified by using conductive-AFM (C-AFM) measurements in space charge limited (SCLC) regime. The obtained current map of the neat PTB7 film is explained in terms of non-uniform built-in voltage and variations of hole mobility. For mobility estimation, the semi-empirical model of SCLC, known from previous works, was modified and applied. It is found that the values of built-in voltage in C-AFM measurements are usually several times larger than ones derived from macroscopic measurements. It is also shown that value of hole mobility in PTB7 film depends on location and varies in more than two times. These mobility variations are connected with nanoscale film structure revealed by other methods.Publisher PD

A New Method for the Synthesis of Bromine-Containing Heterocyclic Compounds for Photovoltaic Polymers

With the development and improvement of systems for converting sunlight into electric and thermal energy, more and more work is emerging on the development of the newest and most promising direction in solar energy, namely the creation of solar cells based on photosensitive polymers. Recently the power conversion efficiency of organic photovoltaic (OPV) devices has overcome the barrier of 17%, and thus we can expect a new wave of scientific interest in the development of new, more efficient OPV devices. Unfortunately, during searching for highly efficient chemical structures of OPV polymers, the researchers missed an important point: all photovoltaic polymers consist of aromatic and heteroaromatic «building blocks», which, in turn, are synthesized based on outdated techniques using highly toxic, dangerous for life and environment precursors. The development of «green», environmentally friendly, economically viable methods for the synthesis of photovoltaic polymers and building blocks for their production, will make the energy obtained from OPV truly «green». In this work, we present an alternative, «green» method for synthesizing halogen-containing aromatic and heteroaromatic, expensive building blocks most commonly used in the synthesis of photovoltaic polymers, which can be used to obtain photovoltaic polymers of various structures. We present the original methods for the synthesis of 4,4-dibromo-1,1- biphenyl (1), 4,7-dibromo-2,1,3-benzothiadiazole (2), 2-bromothiophene (3) and 2,5-dibromothiophene (4). All these methods differ from the previously described routes by their simplicity and convenience of their implementation, the absence of corrosive and irritant reagents, good yield and compliance with the principles of «Green Chemistry»

Study of the local charge transport in photoactive blends based on polymer PTB7

Изучены фотоактивные пленки на основе перспективного полупроводящего полимера PTB7 методами СЗМ. Методом регистрации локального тока растекания изучен локальный транспорт заряда. Определены диапазоны подвижности дырок в различных смесях PTB7.The photoactive films based on promising semiconducting polymer PTB7 are studied by SPM. Conductive-AFM is used for investigation of local charge transport in the films. The ranges of hole mobilities in various compounds are determined.Работа поддержана МОН Республики Казахстан (Программа НУ-Беркли 0115РК03029) и Минобрнауки РФ ГК № 14.578.21.0188 (Уникальный идентификатор соглашения RFMEFI57816X0188)

Local electrical properties of PTB7 film

Abstract A study of the spreading of currents and current-voltage characteristics in a pure PTB7 thin film by atomic force microscopy (AFM) technique was carried out in order to investigate the processes of transport of positive charge carriers in the nanoscale range. It was showed that the numerical values of the carrier mobility can significantly differ on the nanoscale and require correct interpretation of processes with the scale that are comparable with the morphological features of organic solar cells

Photoinduced heating of thin nitrogen-polymer films

https://kpfu.ru/uz-eng/phm/archive/photoinduced-heating-of-thin-nitrogen-polymer_342733.htmlВ работе впервые исследован фотоиндуцированный нагрев полимерных пленок, функционализированных молекулами азохромофора, с использованием сканирующей тепловой микроскопии с нанометровым разрешением. Показано, что при облучении пленки толщиной 800 нм резонансным лазерным излучением (532 нм) и мощностью порядка 25 мВт/см2 наблюдается нагрев пленки на 1.7 К. Предложен также метод определения температуры стеклования тонких (< 100 нм) полимерных пленок на основе термоиндуцированной атомно-силовой микроскопии. Температура стеклования определяется по изменению фазы осциллирующего АСМ-кантилевера. Используя этот подход, в работе показано аномальное снижение температуры стеклования азополимерных тонких пленок без и со стеклянной подложкой

A green chemical method for synthesis of bromine-containing “building blocks” for the production of photovoltaic polymers

Bromine-containing derivatives of aromatic and heteroaromatic compounds are the most important "building blocks" in the assembly of modern Photovoltaic Polymers (PV). While PV is being developed to produce "green" energy, converting sunlight to electricity, the reactions for producing brominated derivatives of building blocks described in the literature are examples of obsolete and environmentally dirty technologies. More environmentally harmful than bromination with molecular bromine [1] can only be bromination by molecular bromine in a concentrated hydrobromic acid medium [2]. Using 1,1'-diphenyl (1), 9H-diphenylcarbazole (2) and thiophene (3) as examples, we successfully tested the bromination of the above objects with a mixture of potassium bromide and bromate in acetic acid as outlined in the diagram