Book Description
The need for sustainable alternatives to fossil fuels is dire. Organic solar cells present a cost-effective, sustainable alternative to their inorganic counterparts, using earth abundant carbon-based semiconducting materials. Herein, the design criteria for novel organic semiconducting polymers exhibiting the photovoltaic effect are examined. Novel donor and acceptor materials were designed for use in bulk heterojunction organic photovoltaic devices. New materials based on benzodithiophene and thienothiophene comonomers (the PBB series of polymers) were synthesized showing power conversion efficiencies as high as 2.04%. Further examination of the PBB series of polymers, namely PBB3, revealed a dipolar effect on charge separation in this polymer. The dipolar effect revealed new design principles which were utilized in the design of the PBIT polymer based on the novel dipyrrololbenzothiadiazole (DPBT) moiety, which employed a strategy to increase the magnitude of the dipole moment of the polymer backbone. Similarly, the PBTZ polymer series was designed to increase the net dipole moment, incorporating the dithiazolopyrrolopyrrole monomer. The PBTZ series revealed the importance of the change in polarity of the excited state over the ground state dipole moment in determining the efficiency of the polymer through theoretical predictions. The study of bulk heterojunction organic photovoltaics is dominated by incorporation of soluble fullerene derivatives as electron-deficient acceptors. Herein, the design, synthesis and testing of non-fullerene small-molecule and polymers as n-type acceptor units is reported.
