The College of Education for Pure Sciences, Department of Physics, reviewed a master's thesis on "Studying the Effect of the Mixing Ratio (Donor/Acceptor) on the Performance of the Active Layer in Organic Solar Cells." The thesis, submitted by researcher Nour Al-Huda Hussein, aimed to study the effect of varying the mixing ratio between the P3HT donor and ICxA acceptor on the optical and electrical properties of the active layer used in Bulk Heterojunction (BHJ) organic solar cells, with the goal of determining the optimal ratio for achieving the best performance in these cells.

The study involved preparing six different mixing ratios for P3HT:ICxA films: (1:0.5), (1:0.8), (1:1), (1:1.2), (1:1.5), and (1:2). The thin films were characterized using AFM techniques to study surface morphology, XRD to study crystal structure, and UV-Vis to determine optical properties. The electrical properties were also studied under both light and dark conditions, as well as the effect of temperature. The results showed that all films had a homogeneous surface and low roughness ranging from 2 to 4 nm. Optical measurements confirmed that sample S4, with a mixing ratio of 1:1.2, exhibited the highest optical absorption, while the absorption coefficient (α > 10⁴ cm⁻¹) indicated that the electronic transitions in all samples were direct.

Electrical measurements also showed that sample S4 (1:1.2) performed best under illumination, outperforming samples S1, S2, S3, S5, and S6 by a factor of 2, 3, 1.8, 3.8, and 2.9, respectively. Furthermore, thermal measurements within the 25–65 °C range demonstrated a convergence between the heating and cooling curves, indicating the stability of the active layer and its ability to maintain its structured composition. Finally, optical modeling using RefFIT software and the Transfer Matrix Method (TMM) supported the experimental results, predicting the highest internal absorption and the highest theoretical current density (Jsc) value for sample S4, confirming that the mixing ratio (1:1.2) represents the optimal ratio between the donor and acceptor material, and can be adopted as a basis for developing higher-performance organic solar cells in the future

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