Ideal diode equation for organic heterojunctions. I. Derivation and application
Organic solar cells require suitable anode surface modifiers in order to selectively collect positive charge carriers and improve device performance. We employ a nickel metal organic ink precursor to fabricate NiO hole transport layers on indium tin oxide anodes. This solution deposited NiO annealed at 250 °C and plasma treated, achieves similar OPV device results reported with NiO films from PLD as well as PEDOT:PSS. We demonstrate a tunable work function by post-processing the NiO with an O2-plasma surface treatment of varied power and time. We find that plasma treatment is necessary for optimal device performance. Optimal devices utilizing a solution deposited NiO hole transport layer show lower series resistance and increased fill factor when compared to solar cells with PEDOT:PSS.