A simple synthesis method to prepare a molybdenum oxide hole-transporting layer for efficient polymer solar cells

Abstract

We report a simple synthetic method to prepare amorphous molybdenum oxide (p-MoO3) using a favorably stable peroxomolybdic acid organosol as the precursor solution prepared by an ultrasonic reaction for the first time.

Facile and low cost oxidative conversion of MoS2 in α-MoO3: Synthesis, characterization and application

“…It is known from the literature that the presence of Mo 5+ species may result in the formation of isolated, occupied gap states close to the conduction band [39]. These states can cause the Fermi level to shift upwards and consequently reduce the work function [40].…”

“…The main characteristic of an oxygen deficient material is the increase of the free electron concentration [38]. Usually, it can be evidenced by an increase in the conductivity and a strong optical absorption [40,41]. Furthermore, the oxygen ion vacancies of the MoO3−x are occupied by two electrons and acted as donor centers and the charge transfer from oxygen vacancies to Mo ions creates reduced states of Mo +5 [40].…”

“…Usually, it can be evidenced by an increase in the conductivity and a strong optical absorption [40,41]. Furthermore, the oxygen ion vacancies of the MoO3−x are occupied by two electrons and acted as donor centers and the charge transfer from oxygen vacancies to Mo ions creates reduced states of Mo +5 [40]. The low work function could be related with amount of Mo +5 species.…”

“…The low work function could be related with amount of Mo +5 species. It can be responsible to influence the built-in electric field of the devices and the photocurrent being extracted at short-circuits with low efficiency [40]. Note that the band gap from Tauc's method (Fig.…”

“…We can observe similar cell parameter for 500 and 2000, and the same effect can be observed for 1000 and 3000 rpm. It is known that the HTL should be thick enough to act as a protection layer, preventing the Ag diffusion into the active layer [40]. Therefore, the spin coating speed of the 1000 rpm was chosen to allow the best parameters for solar cell and to show the lowest standard deviation with higher reproducibility.…”