Continuous Spray pyrolysis (CoSP) synthesized ZnO/TiO2 nanostructure based perovskite solar cells

Efficient, easily processable and low-cost solar cell absorber materials represent the core-target of current photovoltaic research. Several successful device architectures have been reported with varying electron and holes elective contact materials. This project is basically on the development of perovskite solar cells which has a planar structure without the scaffold metal oxide layer. The holes and electrons generated in the perovskite layer are transported through the hole-collection and electron-collection layers, respectively, to the two electrodes. The advantages of this structure are the simplicity as well as low-temperature solution processability. The first big breakthrough in device architecture was in part a result of employing the organic hole-conductor 2,2’,7,7’-tetrakis (N,N-di-p-methoxyphenyl-amine) 9,9’- Spirobifluorene (Spiro-OMeTAD), delivering solar cell efficiencies of around 15%. However, the spiro-OMeTAD has a price at research scale that is more than 10 times that of gold and platinum. There is therefore good motivation to develop perovskite cells based on already scaled “commodity” hole-conductors such as CuSCN, CuI, polyaniline, Poly(3,4- ethylenedioxythiophene) (PEDOT), MoO3 amongst others.

For the same purpose, MoO3 nps were synthesized by CoSP reactor to be utilized as a hole-extraction layer because MoO3 has merits of high transparency, high work function, and high conductivity. The PL spectrum for the MoO3/perovskite film was significantly quenched which indicates that charge transfer process has occurred from the perovskite to the HTL. It indicates that the MoO3 film extracts holes efficiently, which may decrease charge recombination in devices and thus in a way proves the value of the CoSP generated MoO3 layer. This technique does not require any post treatment as required in other solution processed techniques, e.g., the O2 plasma treatment required to remove the dispersing agent in commercially available nanoparticle suspension. This technique is also favorable in terms of rapid and large scale production of the nanoparticles.