Modeling On Optical Constants And Film Thickness Of Blend Active Layer And Application For Organic Photovoltaic Device

The organic photovoltaic cells (OPVs) have gained considerable attention due to their meritsof lower production costs, convenient design/synthesis of new materials, flexible substrate basedroll-to-roll process, wide applications, simple device structure and transparency. Recent goal inorganic photovoltaic cells study is to improve the power convertion efficience and stability, hencewide commercial application can be realized.This thesis focuses on the optical constants and film thickness of bulk hetero junction of smallmolecule organic devices and optical modeling for device efficiency improvement.Firstly, taken the blending of copper phthalocyanine (CuPc) and fullerene (C60) as an example,a simple, convenient and low-cost method for the determination of the optical constants and filmthickness of blended organic thin films has been demonstrated. New scheme for optical modelingof blended organic thin film was proposed by introducing peak energies of Cody-Lorentzoscillators of the pure materials, which were determined by fitting the film absorption of purematerials. These oscillators of pure materials could be recognized in the transmittance spectrum oftheir blends, and were further used as the initial searching ranges in the simulation of blendedfilms. As a result, the constraint bounds of the unknown parameters were significantly reducedand modeling efficiency as well as fitting accuracy was improved. For instance, the fitting of thetransmittance curves of blended films with different blending ratios all reached reliable results incomparison with extinction coefficients obtained from experiment, with the error under5%.Secondly, we model the electromagnetic field distribution and exciton generation rate of smallmolecule organic bulk hetero junction devices based on CuPc: C60. Combining of the researchresults of first part, normalized electromagnetic field distribution and exciton generation rate oforganic photovoltaic device can be calculated. The thickness of CuPc:C60blend and C60layerare optimized with the selected wavelength after the analysis of absorption spectra. Then theelectromagnetic field distributions of planar and bulk hetero junction devices with different blendratio are in conparision with the experimental results. Finally, the optimized thickness of activelayer is obtained according to exciton generation rate.