Performance Optimisation and Stability Assessment of ITO/ZnO/PM6:ITIC/PEDOT: PSS/Graphene Organic Solar Cell: A Comprehensive SCAPS‑1D Study

Abstract

Non‑fullerene organic solar cells based on PM6:ITIC have surpassed 11 % efficiency, but the use of a graphene top anode in inverted architectures remains underexplored in device modelling.This work investigates an inverted organic solar cell with the architecture ITO(cathode)/ZnO/PM6:ITIC/PEDOT:PSS/ graphene(anode) using the Solar Cell Capacitance Simulator (SCAPS‑1D). The calibration uses two tiers: an ideal low‑defect model reproduces the experimental efficiency of PM6:ITIC devices (11.76 %,  mA cm⁻²,  V,  %), while a realistic defect density ( cm⁻³, capture cross‑sections =  cm²) restores a physical thickness optimum. Device optimisation yields an active layer thickness of 200 nm, a ZnO electron transport layer of 30 nm with a donor density of  cm⁻³, and a PEDOT:PSS hole transport layer of 10 nm, to give a final power conversion efficiency of 10.60 % ( mA cm⁻²,  V,  %). The graphene anode work function must exceed 4.4 eV for optimal hole extraction; pristine monolayer graphene (4.5 eV) already lies within the saturation region. Temperature‑dependent simulations (280–380 K) reveal a positive voltage coefficient of  characteristic of Shockley–Read–Hall recombination through mid‑gap traps. External quantum efficiency spectra show broader photon collection in the optimised device than in the baseline. Taken together, the results yield quantitative design guidelines for graphene‑electrode non‑fullerene organic solar cells and establish the value of SCAPS‑1D as a predictive simulation tool