Organic p-i-n solar cells-The role of energy levels in absorber and charge trasnport layers
Speaker: Wolfgang Tress, Technical University, Dresden, IAPP
Series: Topical Seminars
Location: Engineering Quadrangle J401
Date/Time: Tuesday, December 6, 2011, 2:00 p.m. - 3:00 p.m.
This talk discusses experimental and drift-diffusion simulation data of flat and bulk heterojunction solar cells with injection and extraction barriers at the contacts. The barriers are realized by a combination of p-type materials with HOMOs varying between -5.0 and -5.6 eV as hole transport layer (HTL) and as donor in multilayer p-i-n solar cells. The experimental J-V curves are compared to simulation data of the device stack and can be qualitatively reproduced and explained by the calculations. In particular, the influence of these barriers on the open-circuit voltage and on the shape of the current-voltage characteristics (J-V curve) is discussed. It is shown that barriers can cause S-kinked J-V curve which significantly decrease the power conversion efficiency.
The second part of this talk focuses on bulk heterojunction ZnPc:C60 solar cells with varied mixing ratios. Here, it is observed that the open-circuit voltage depends on the mixing ratio. Possible reasons for this dependency are discussed examining J-V and photoelectron spectroscopy data.