Enhanced performance in bulk heterojunction solar cells with alkylidene fluorene donor by introducing modified PFN-OH/Al bilayer cathode

Abstract

We report bulk heterojunction solar cells with benzothiadiazole-containing polyalkylidene fluorene (PAFBToBT) donors made by introducing 2,4,7,9-tetramethyldec-5-yne-4,7-diol (Surfynol 104)-doped poly[9,9-bis(6′-(diethanolamino)hexyl)-fluorene] (PFN-OH) as an interfacial layer to enhance power conversion efficiency (PCE) and stability. Surfynol 104 has amphiphilic characteristics, and it supports the formation of a homogeneous interfacial layer on the photoactive layer. In addition, the application of the Surfynol 104-doped PFN-OH interfacial layer prevented the decrease in absorption of photons in the photoactive layer and improved the photocurrent density (J_SC) by increasing the electron mobility. Therefore, J_SC and the fill factor increased to 10.5 mA cm⁻² and 49%, respectively, and the calculated PCE was 4.8%. In addition, a modified bilayer cathode system was introduced to the PCDTBT and the P3HT-based PSCs, and the PCE improved to 5.3% and 3.9%, respectively. Moreover, the in-air stability was enhanced.