Enhancing Efficiency and Performance of Non-Fullerene Acceptor-Based Organic Solar Cells with Graphene Interlayer via Numerical Simulation

Abstract

Non-fullerene acceptor (NFA) based organic solar cells (OSCs) have the potential to be low-cost and highly efficient next-generation solar cells via interfacial engineering. Herein, we adopt a computational approach to analyse the effect of surface passivation material (graphene) in reducing interfacial recombination while also promoting the extraction of holes in an OSC architecture with the absorbing layer comprising a donor polymer poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl] (PTB7-Th) and an NFA 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(5-hexylthienyl)-dithieno[2,3-d:2’,3’-d’]-s- indaceno [1,2-b:5,6-b’]dithiophene (ITIC-Th). SCAPS-1D software was used to model the impact of the graphene layer in the NFA-OSC by analysing the thicknesses of the graphene, absorbing layer, and hole transport layer (HTL), coupled with the analysis of the doping concentration of the HTL, the defect density of the absorbing layer, the interfacial defect densities at the absorbing layer/graphene and the graphene/HTL with the device structure: ITO/ZnO/PTB7-Th: ITIC-Th/Graphene/PEDOT: PSS/Au. A power conversion efficiency (PCE) of 6.2163% was obtained during the initial simulation of the device without graphene, while a PCE of 11.6607% was obtained for the device with graphene, showing a low recombination effect in the device. Upon carefully optimising the design of the device with graphene, an efficiency of 20.1967% was obtained, a 73% increase in efficiency over the initial design. This study demonstrates that the addition of adding graphene as a layer, helps to mitigate loss in energy and improves electric charge flow, making this solar cell efficient.