Improved charge transport via WSe2-mediated hole transporting layer toward efficient organic solar cells

Transition metal dichalcogenides (TMDs) have received significant attention because of their potential for replacing or modifying the existing charge transporting materials in organic solar cells (OSCs) with their unique crystalline structure and desirable electrical properties. Poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has been considered as the representative hole transporting material owing to its notable optical transmittance, electrical conductivity, and solution-processability. In this study, we provide a facile method to introduce a liquid-phase exfoliated TMD, tungsten diselenide (WSe2), as the device performance enhancer in OSCs. Implementation of WSe2 into PEDOT:PSS without significant change to the surface morphology mediates effective charge transport in the completed device. The phase separation of PEDOT and PSS induced by the WSe2 provides a conductivity enhancement in the modified hole transport layer (HTL), which contributes to the increase of hole mobility and decrease of charge recombination loss in the OSCs, resulting in the improvement of power conversion efficiency from 7.3% to 8.5% for pristine and modified HTL devices, respectively. These results provide a simple strategy for the enhancement of device performance in OSCs, demonstrating their promising potential in the application of TMDs for next-generation energy harvesting devices.