The specific optical absorption of an organic semiconductor is critical to the performance of organic optoelectronic devices. For example, higher light-harvesting efficiency can lead to higher photocurrent in solar cells that are limited by sub-optimal electrical transport. Here, we compare over 40 conjugated polymers, and find that many different chemical structures share an apparent maximum in their extinction coefficients. However, a diketopyrrolopyrrole-thienothiophene copolymer shows remarkably high optical absorption at relatively low photon energies. By investigating its backbone structure and conformation with measurements and quantum chemical calculations, we find that the high optical absorption can be explained by the high persistence length of the polymer. Accordingly, we demonstrate high absorption in other polymers with high theoretical persistence length. Visible light harvesting may be enhanced in other conjugated polymers through judicious design of the structure.

Nature Materials (2016) doi:10.1038/nmat4645

http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4645.html

中文报道：有机半导体中的光学吸收对于有机光电子器件性能至关重要。例如，更高的光学捕获率能够为太阳能电池带来更高的光电流，从而突破目前太阳能电池中电子传输的瓶颈。英国科学家通过对比40余种共轭聚合物发现：很多不同的化学结构在相对较低的光子能量下都具有极高的光学吸收率。通过研究骨干结构的构造并结合理论计算，他们发现聚合物高的相关长度（λp）对于高光学吸收起着重要作用。他们利用这一理论设计了其它高光学吸收的聚合物。这一理论对于设计能够大幅提高可见光吸收的聚合物具有指导意义。（新材料在线）。