2.1.2. Suspension Preparation

CCO and Mg:CCO nanoparticles were dispersed into 2-MOE to make 2 mg mL−<sup>1</sup> suspensions for materials characterization and fabrication of P3HT:PC61BM OSCs, PFBT2Se2Th:PC71BM OSCs, PTB7-Th:ITIC OSCs, and MAPbI3 PSCs. Just prior to film preparation, the suspensions were placed into a bath sonicator (Branson 3510, Plano, TX, USA) for 90 min, then filtered through a 1 μm PTFE filter (Thermos scientific, Titan3, Houston, TX, USA), re-sonicated for 90 min, and again filtered through a 0.45 μm PTFE filter (Biomed Scientific, Seattle, WA, USA).
