Scalable and Green Fabrication of Thin-Film Solar Cells Using Solution Processed Inkjet Printing Method

Abstract

Inkjet printing has recently emerged as a scalable and green processing method to develop thin film electronics.[1-8] Here, we report a low-cost and efficient inkjet printing method for the development of a solar cell device. The commonly used electron collection layers require high post- sintering temperatures (~ 500° C) which are unfavorable for plastic and textile-based substrates. The electron transport layer was constructed by reduced graphene oxide – TiO2 nanocomposite ink which was uniformly printed over the plastic and FTO substrates. The graphene in the nanocomposite provides excellent charge-collection due to its high conductivity and enables device fabrication at low processing temperatures. The other components of the solar cell were also deposited over the electron transport layer. The developed solar cell with reduced graphene oxide – TiO2 electron transport layer shows good photovoltaic performance with a power conversion efficiency of ~ 21 % which was 30 % higher than the TiO2 based electron transport layer. The comparative impedance spectra also confirm that the improvement in the photovoltaic performance was due to the better charge collection generated by the reduced graphene oxide layers. The device also shows excellent stability with 94 % retention of the initial power conversion efficiency after storing it in an ambient condition with a relative humidity of ~ 40 % for 120 h. The device with plastic substrate also displays good flexibility with negligible change in the device performance in the flexed conditions. The desirable output for solar cell devices can be easily achieved by changing the ink concentrations, number of printing layers, and by replacing the size and shape of the digital drawings. So, the inkjet printing technology has a huge potential for the development of thin, low-cost, scalable, and flexible solar cell devices.