To enhance the power conversion efficiency (PCE) and stability of all-polymer solar cells (all-PSCs), a new precursor solution based on an in situ chemical reaction of nanomolybdenum powder (Mo), hydrogen peroxide (H2O2), and ammonia (NH3·H2O) was developed for preparing a MoO3 hole transport layer (HTL) for all-PSCs. The results showed that the PCE and stability of PM6:PY-IT solar cells based on the MoO3 HTL were better than those based on a PEDOT:PSS layer. To further understand the relationship between the HTL and the device performance, ultrafast photophysical processes of all-PSCs based on different HTLs were contrastively analyzed. Our research indicated that the micromorphology of active layers could be influenced by the interfacial layer material, consequently determining the photoelectric conversion process of all-PSCs. The MoO3-based all-PSCs had longer charge lifetime, higher charge mobility, and lower charge recombination characteristics compared with the devices based on the PEDOT:PSS layer during the operation time. As a result, the MoO3-based PM6:PY-IT solar cells achieved an initial PCE of 15.2%, and they still maintained more than 80% of their initial efficiency after 1000 h.
Keywords: all-polymer solar cells; device stability; hole transport layer; morphology of active layers; photoelectric conversion process.