Structure‐Property Optimizations in Donor Polymers via Electronics, Substituents, and Side Chains Toward High Efficiency Solar Cells

Abstract

Many advances in organic photovoltaic efficiency are not yet fully understood and new insight into structure‐property relationships is required to push this technology into broad commercial use. The aim of this article is not to comprehensively review recent work, but to provide commentary on recent successes and forecast where researchers should look to enhance the efficiency of photovoltaics. By lowering the LUMO level, utilizing electron‐withdrawing substituents advantageously, and employing appropriate side chains on donor polymers, researchers can elucidate further aspects of polymer‐PCBM interactions while ultimately developing materials that will push past 10% efficiency.

Charge carrier mobility of the organic photovoltaic materials PTB7 and PC71BM and its influence on device performance

“…1(b) and reveal only very weak field dependence. Our value of the hole mobility in PTB7 is slightly higher compared to results found by space charge limited current (SCLC) measurements, which were reported in the range 2-5.8 Â 10 À4 cm 2 /Vs [16][17][18][19]. The TOF mobility of PTB7 is almost one order of magnitude higher than that of P3HT for which reported values are about 2 Â 10 À4 cm 2 /Vs [20].…”

Dramatic performance enhancement for large bandgap thick-film polymer solar cells introduced by a difluorinated donor unit

“…The general theory for D-A conjugated polymers is that modifying the donor unit is more effective in tuning the HOMO level and a similar effect applies to modifying the acceptor unit for tuning LUMO levels [43][44][45]. The ffT2 donor unit appears to be a useful building block in tuning LUMO levels and could be combined with other acceptor units to obtain D-A polymers with smaller LUMO offsets with PCBM.…”

Advances in the synthesis and application of isoindigo derivatives

“…Some aspects of these isoindigo properties were briefly discussed in some reviews. [88][89][90][91][92] Synthetic applications of isoindigo are mainly based on the creation of polymeric structures. Variation of substituents both at the nitrogen atom and the side chain is directed towards improving the physical and chemical characteristics of the target compounds: solubility, UVvisible absorption, electron affinity and others.…”