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

Effect of molecular weight on the photovoltaic performance of a low band gap copolymer blended with ICBA

In this work we fabricated solar cells by combining ICBA as electron acceptor material with various weight fractions of a low band gap electron donor copolymer based on 2,1,3-benzothiadiazole, thiophene and thieno[3,2-b]thiophene units (labeled PPBzT2-CEHb), whose structure is given in Fig. 1 [1]. We investigated the influence of the polymer molecular weight and post-deposition annealing temperature on the solar device performances. Charge transport in pristine polymer films was also studied by measuring the field-effect hole mobility in bottom contact field-effect transistors (OFET)

Nanoscale mobility mapping in semiconducting polymer films

© 2020 Elsevier B.V. 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

Nanoscale mobility mapping in semiconducting polymer films

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.</p

Polymeric materials as photovoltaic materials for solar cells

Investigation revealed that alkyl chains in beta-position (fourth position of thiophene rings) lead to better pi-electron delocalisation due to enchanced planarity, because such position avoids rotational hinderance. Also, ramified alkyl side chains were found to be more appropriate for giving the compound better solubility. Additionally, change from linear alkyl chain to ethylhexyl branched solubilising side chain affected interaction between fullerene and polymer in bulk heterojunction devices. Synthesis of PPTDT2-CEHβ copolymer based on this chemical structure was performed and its physical and optoelectronical properties were studied as well