The structure optimization design of the organic solar cells using the FDTD method

The finite-different time-domain method (FDTD) was used to optimize structure of organic solar cells based on the heterojunction of the substituted polythiophene polymer (PEOPT) and the C₆₀ molecule. The absorption of the device in visible light range was determined, and the maximized average absorption is about 88% at the wavelength of 469 nm. The effects of the glass substrate thickness on the absorption and the distribution of the optical energy inside the device were investigated. Based on the important roles of the optical energy at PEOPT/C₆₀ interface in the photocurrent efficiency, the device structure was optimized for the maximized photocurrent efficiency. The optimal C₆₀ thickness 29 nm was obtained for the wavelength of 469 nm. Meantime, when the PEOPT thickness is the range of 80-130 nm, there are few effects on optical energy at PEOPT/C₆₀ interface.