Organic solar cell (OSC) is one of the best promising candidate for harvesting energy mainly due to their simple and economic fabrication process, the reduced manufacturing cost, and easy integration to other products. Bulk heterojunction solar cell in which the active layer is a blend of donor –acceptor materials are one of the best organic photovoltaic device with highest efficiency and a significant improvement in the device performance occur over last years. Bulk heterojunction architecture gives a high interfacial surface area for efficient charge dissociation. In this study, bulk heterojunction solar cell is simulated using General Purpose Photovoltaic Device Model Software. A donor-acceptor blend of Zinc pthalocyanine (ZnPc) fullerene C60 is used as the active layer. The power conversion efficiency for various thickness of the active layer is studied. Optimization of active layer thickness for maximum power conversion efficiency are done. The dependence of various electrical parameters such as short circuit current density(Jsc), Open circuit voltage(Voc), fill factor (FF), average carrier mobility on power conversion efficiency are also studied.

Organic based thin film solar cells have achieved considerable power conversion efficiency (PCE). As there is a desire to the benefits of on-demand energy production, future world energy consumption will continue to rise. Bilayer organic solar cell has two active layers in between conductive electrodes. Present report, is a simulation study to compare the PCE of bilayer organic solar cells by varying one of its active layer material using General-Purpose Photovoltaic Device Model or GPVDM software. The materials used for active layer are MEH-M3EH-PPV, MEH-DOO-PPV, MEH-PPV and M3EH-PPV based on the degree of alkyl substitutions. Data of absorption spectrum, refractive index spectrum and photoluminescence spectrum are added as input and obtained the simulation results. Values of power conversion efficiencies, fill factor and other photovoltaic parameter values for each bilayer organic solar cell is obtained. Transmittance spectrum, reflectance spectrum, Current density-Voltage plot, variation of charge density and total charge density with applied voltage are attained from the simulation and compared. The results give out effect of side chain alkyl substitution on efficiency of bilayer organic solar cell. MEH-DOO-PPV with longest alkyl side chain substitution has maximum power conversion efficiency. This intuition helps to design suitable bilayer organic solar cell, which has got its relevant applications in the optoelectronics.