Highly Efficient and Stable Organic Solar Cells Enabled by a PEDOT:PSS/H<i><sub>x</sub></i>MoO<sub>3</sub> Hybrid Hole Transport Layer
Fei Jin, Ruixiang Peng, Yi Qiu, Jinna Zhang, Ziyi Ge
Abstract
The hole transport layer (HTL) is an essential factor to improve the charge carrier transport and collection of organic solar cells (OSCs) and also has an important impact on the stability of the device. The commonly used HTL material poly(3,4-ethylenedioxythiohene):poly(styrenesulfonate) (PEDOT:PSS) affects electrical conductivity due to the significant proportion of insulated PSS, and the characteristics of easily absorbing water and oxygen in air are often reported to shorten the OSC lifetime. The modification of PEDOT:PSS by H x MoO 3 with high conductivity and good stability was prepared by a low-temperature solution. The results of Raman spectroscopy showed that the addition of H x MoO 3 could promote the transformation of the curled benzoyl structure in the polymer PEDOT:PSS into a linear quinone structure, which enhanced the charge transport capacity of the hybrid HTL. In addition, the dense PEDOT:PSS film can evenly distribute H x MoO 3 nanoparticles and form a coating effect on them. This can effectively avoid the agglomeration effect of H x MoO 3 nanoparticles and the detrimental effects of particle surface roughness on the device. A transparent and highly conductive hybrid HTL film was prepared to improve the short-circuit current density ( J sc ) and fill factor (FF) of the device, ultimately leading to the power conversion efficiency (PCE) of the PM6:Y6-based conventional device reaching 17.59% by combining the benefits of high surface flatness of the PEDOT:PSS film and high conductivity of the H x MoO 3 film. In terms of stability, the performance of devices using hybrid HTL can still maintain 57.7% of the initial value after 400 h storage in an 85 °C nitrogen environment and FF can maintain 71.9% of the initial value, and the subsequent stability decline trend remains stable. The results demonstrate that hybrid HTL can effectively increase the efficiency and environmental stability of OSCs.