Design and synthesis of diketopyrrolopyrrole-CdS hybrid nanostructures for enhanced photovoltaic applications

An innovative hybrid nanostructure composed of diketopyrrolopyrrole (DPP) oligomers and cadmium sulfide (CdS) nanoparticles was developed to enhance the efficiency of organic– inorganic photovoltaic devices. The DPP-CdS hybrids were synthesized via a solution-phase mixing method, resulting in uniform nanoparticle dispersion along polymer fibrils and strong interfacial coupling. Structural characterization confirmed the coexistence of crystalline CdS domains and partially ordered DPP phases, while spectroscopic analyses indicated notable redshifts and band broadening, evidencing electronic interactions at the interface. The hybrid material displayed significantly broadened light absorption across the 400–700 nm range and an optimized optical bandgap of ~1.92 eV. When implemented in inverted bulk heterojunction solar cells (ITO/PEDOT:PSS/DPP-CdS/PC71BM/Al), the active layer enabled a short-circuit current density of 11.3 mA/cm², open-circuit voltage of 0.82 V, and a power conversion efficiency (PCE) of 5.93%—more than double the PCEs of devices with only DPP (2.61%) or CdS (1.35%). External quantum efficiency exceeded 60% at peak wavelengths, confirming efficient exciton generation and charge extraction. Furthermore, electrochemical impedance spectroscopy showed a reduced charge transfer resistance of 238 Ω, while transient photovoltage measurements revealed an extended carrier lifetime of 6.10 μs, indicating minimized recombination losses. These improvements are attributed to favorable energy level alignment, enhanced morphology, and interfacial engineering in the DPP-CdS hybrids. This work demonstrates the potential of combining conjugated organics with tailored inorganic nanostructures to overcome current performance limitations in hybrid photovoltaics and provides a scalable strategy for nextgeneration solar energy materials.