Bootstrap kernel for organic low dimensional systems; PPV, pentacene and picene

We apply the bootstrap kernel within time dependent density functional theory to study one-dimensional chain of organic polymer poly-phenylene-vinylene and molecular crystals of picene and pentacene. The behaviour of this kernel in the presence and absence of local field effects is studied. The absorption spectra of poly-phenylene-vinylene has a bound excitonic peak which is well reproduced by the bootstrap kernel. Pentacene and picene, electronically similar materials, have remarkably different excitonic physics which is also captured properly by the bootstrap kernel. Inclusion of local-field effects dramatically change the spectra for both picene and pentacene. We highlight the reason behind this change. This also sheds light on the reasons behind the discrepancy in results between two different previous Bethe-Salpeter calculations.