The synthesis of MoO3 nanoparticles is reported using a Continuous Spray. Pyrolysis (CoSP) reactor and the influence of zone temperature, precursor concentration on the structural and morphological properties is investigated. The collected nanoparticles are utilized to prepare thin films by spin coating and further annealing at various temperatures. The improvement in morphology, crystallinity and the band gap shift shows the effectiveness of the annealing treatment in creating a proper hole transport layer for device applications. The technique thus allows the film formation using a non-vacuum method well suited for organic solar cells. The CoSP based MoO3 (CoSP_MoO3) films are demonstrated to have equal performance to hole-injection layers composed of thermally evaporated MoO3 (eMoO(3)).