Overview of printing and coating techniques in the production of organic photovoltaic cells

The organic photovoltaic cell (OPV) is composed of multiple layers, and some printing and coating techniques are more suitable than others for a certain type of layer. This paper aims to characterize and compare the most relevant coating and printing techniques that can be used in the manufacture of OPVs. Extensive bibliographic research was carried out on articles published from 1998 to 2020 to identify various aspects OPV, such as the principle of operation, advantages, disadvantages, and which layers can be printed by each technique. The results show that the most used method for the processing of OPVs is spin-coating. In the studies found, rotation was used to coat the active layer, the electron transport layer, and the hole transport layer. The techniques of pad printing, casting, and meniscus are considered useful in the processing of the active layer. Regarding the deposition of the active layer, hole transport layer, electron transport layer, and anode, the rotogravure, crack matrix, spraying, and brushing techniques were satisfactory. Flexography has been used to form the active layer, electron transport layer, and anode. Screen printing, inkjet printing, and knife/blade coating were used in the processing of the active layer, hole transport layer, electron transport layer, anode, and cathode. All the double slot die coating, curtain coating, and slide coating allows simultaneous processing of multiple layers. Techniques compatible with roll-to-roll processing are more likely to be at the center of OPVs in the future, thus making solar photovoltaic technology more competitive.