Despite the many successful applications of TD-DFT on a wide range of molecular systems, it is often challenging in TD-DFT to calculate a sufficient number of excited states for a complete spectrum or spectra of extended biological systems. To overcome this challenge, the Grimme group presented two highly efficient approaches, the simplified Tamm-Dancoff-Approximation (sTDA) and simplified Time-Dependent Density Functional Theory approach (sTD-DFT). In both approaches, the computational resources needed to tackle a targeted system is solely determined by the ground state DFT calculation. This is achieved by approximating Coulomb and exchange interactions of the electrons by monopole interactions.