Due to tremendous synthetic effort and keen physical insight, organic solar cell efficiency has increased to over 16%. By far the most common design is the bulk heterojunction (BHJ) where two materials are blended to form a nanoscale phase separated material that separates charges at the interface of electron donors and acceptors. We present a detailed balance model that suggests that BHJ materials with exciton binding energies of 0.2-0.3 eV should not be expected to perform significantly better that the current state of the art. In addition, the efficiency of champion devices is recognized as less important than several other factors including device stability, low synthetic complexity and robustness to processing conditions. For these reasons, attention is turning towards single-component cells. We present a design for a fully-conjugated block polymer that we term a double heterojunction. Detailed balance considerations suggest that device efficiencies approaching 30% are possible with exciton binding energies of 0.2-0.3 eV. The design calls for a fully conjugated diblock polymer for which optimal nanoscale morphology is the thermodynamically favored state. The key to limiting charge carrier recombination and achieving the highest efficiency is a conjugated linker between the electron accepting and electron donating portions of the diblock system, called a bridge. Self-consistent field calculations show that energy level alignment between the acceptor and donor segments can be optimized independently and that optimal bridge alignment results from a composition made from equal parts of the donor and acceptor segments. Taken in sum, the results provide a point-of-entry for a disruptive class of energy harvesting materials.<br/>

Towards thirty: Designs for single-component organic solar cells

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.