AMPS-1D modeling of P3HT/PCBM bulk-heterojunction solar cell

An effective medium model using AMPS-1D (Analysis of Microelectronic and Photonic Structure) simulation program was shown to be applicable for bulk heterojunction polymer solar cell modeling. The model was successfully applied to P3HT/PCBM bulk heterojunction solar cell; the simulation results show that in P3HT/PCBM with ohmic contacts the open circuit voltage is governed by the LUMO of the acceptor and the HOMO of donor with a total voltage loss of 0.37 V. The efficiency of the photovoltaic device was greatly enhanced by increasing the interface band gap E_gi which is the energy different between HOMO of the donor and LUMO of the acceptor. The results show that by increasing the interface band gap from 1.0 eV to 1.6 eV the efficiency increases from 3.58 % to 8.29 %. Decreasing the donor optical band gap results in a maximum efficiency of 7.32 % when the value of the optical band gap is 1.5 eV (the absorption window is 385 nm). By combining both effects the maximum efficiency was found to be 9.34 % for an optical band gap 1.63 eV. Further, the influence of the back contact potential barrier on the performance of the solar cell was studied. The result shows that for non-ohmic contact the open circuit voltage is highly correlated with the difference of work functions of the two electrodes.