New polythiophene derivatives and enhanced photovoltaic effect by a boron compound blended with them in OPVs cells

Photophysical Study of Polymer-Based Solar Cells with an Organo-Boron Molecule in the Active Layer

“…The detailed fabrication and characterization of our solar cells based in P1–P4 have been reported elsewhere [ 24 , 25 ]. All our OPV cells were fabricated under room conditions and with an inexpensive method for electrode deposition without the use of a vacuum chamber.…”

“…It is observed that there is an overlap between the P1–P4 emission region and the M1 absorption band that, in principle, could lead to an energy transfer mechanism at short interaction range (Förster energy transfer). Nonetheless, this mechanism in our films is rather weak and limited by the fact that the polymers have low fluorescence quantum yields (0.15, 0.13, 0.10, and 0.12 for P1, P2, P3 and P4 in solution, respectively [ 24 ]). In addition, it has been reported that for polythiophenes with a low ionization potential, as those considered in this work, photoluminescence quenching is induced when PC 61 BM is added in concentrations above 5% by weight [ 34 , 35 ].…”

“…Our attention focused on the use of low cost and easily synthesized nonregioregular polythiophenes. For this purpose, in previous work, we synthesized four new polythiophene derivatives (P1–P4) [ 22 , 24 , (P1 corresponds to PC, P2 to PI, P3 to PD, and P4 to PA)] and built photovoltaic cells with a BHJ architecture containing fullerenes and the organometallic borinate molecule 6-nitro-3-(E)-3-(4-dimethylaminophenyl)allylidene)-2,3-dihydrobenzo[d]-[1,3,2]-oxazaborole (M1) [ 19 ]. The series of polymers P1–P4 lack the robustness of other semiconducting materials ( i.e.…”

“…, P3HT), widely used in efficient OPVs. This is due mainly to the low regioregularity of P1–P4 [ 24 ]; however, since the synthesis of our polythiophenes is based on FeCl 3 oxidative polymerization, it allows versatile and mild reaction conditions for industrial-scale production at low cost, avoiding the use of expensive catalyzers commonly employed in other synthesis schemes.…”

“…Figure 1 shows the chemical structure of the materials employed in this study. We found that the low conversion efficiencies of the cells increased by a factor of approximately two upon addition of the borinate [ 24 , 25 ]. At the time of those studies, we did not understand the efficiency enhancement mechanism.…”