Design Principles for Block Polymer Organic Double Heterojunction Solar Cells

An organic double heterojunction photovoltaic device is described and the limits of its power conversion efficiency are investigated via numerical calculation. In the absence of exciton binding energy, fully conjugated block polymer devices exhibit power conversion efficiencies slightly exceeding the Shockley-Queissar limit. As exciton binding energy increases, a decrease in efficiency occurs, but remains over 20% for binding energies less than 0.5 eV. Further calculations show that devices require a high degrees of phase purity to leverage the full benefit of the double heterjunction structure. Synthetic targets are identified and their maximum efficiency is calculated based on experimentally measured energy levels, leading to a generalized structural motif.