Theoretical studies of squaraine and functionalized 2,1,3-benzothiadiazole molecules for solar cell applications

Research on alternative renewable energy sources is of great interest because of increasing world energy demand and depleting non-renewable energy resources. Both organic and inorganic solar cells are an important category of alternative energy resources. Inorganic solar cells, being the most successful technology has demerits such as high cost, rigidity etc. Organic solar cell is a better alternative with power conversion efficiency more than 17%. Squaraine is an important class of electron donating compounds which has high absorption and emission in the visible to near IR region. Organic photovoltaic devices with squaraine-fullerene systems attained 8% power conversion efficiency, which denotes that squaraine compounds have the potential for future organic solar cells. Organic materials consisting of 2,1,3-benzothiadiazole as core functionalized with different chromophore and squaraine as arms and vice versa may be a potential molecule for the fabrication of various organic electronic devices. By understanding the band gap, excitation energies and light-harvesting capability the designed molecules can be effectively used in solar cell applications. Here we designed and studied different squaraine containing molecules whose geometry optimization and band gap calculations are done by time-dependent DFT method.