Amphiphilic Additives Enable the Preparation of Efficient Organic Photovoltaics by Spontaneous Spreading Process.

The spontaneous spreading (SS) process is one of the solution-processed technologies for preparing organic photovoltaics (OPVs). As a broadly used solvent in OPV preparation, chloroform is rarely applied in the SS process since the chloroform-based active layer solution generally forms a wrinkled film, which limits the performance of the devices. In this work, an SS process is developed with amphiphilic additives to prepare efficient OPVs using chloroform as the solvent. By adding amphiphilic additives into the chloroform solution, the interfacial tension between the chloroform solution and water can be tuned finely, and a uniform active layer film can be formed on the water surface. Adopting SS-PM6:Y6 film as the active layer, the SS-OPV is successfully prepared in open-air conditions, and the device performance is comparable to the device prepared by the spin-coating method. Notably, the OPV device using recycled SS-PM6:Y6 film is also demonstrated to present an efficiency of over 14%.