Printable anodes for flexible organic solar cell modules

The performance of organic bulk donor/acceptor heterojunction solar cells with different transparent electrodes is compared. Up to now, expensive material like indium-tinoxide (ITO) has been commonly used as a transparent electrode. Nevertheless, an interesting organic alternative in the form of highly conductive poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) is emerging. In this work, a comparison is made between cells with either ITO or highly conductive PEDOT/PSS as a transparent contact. Different techniques such as spin-coating and screen-printing are used to deposit this latter material. Owing to still limited conductivity of PEDOT/PSS with respect to ITO, an underlying metallic grid is introduced. A standard photographic technique optimised here to result in a metallic Ag-pattern is used. In this way, a comparable performance of the photovoltaic devices with either type of anodes is obtained. This newly developed PEDOT/PSS-based transparent anode is successfully applied onto flexible substrates. Furthermore, appropriate design of the device structure makes it possible to realise serially connected solar cells. The performance of such devices is also reported. These results show that industrial production of fully flexible organic solar cell modules will be possible at low costs.