Electrodeposited NiO anode interlayers: Enhancement of the charge carrier selectivity in organic solar cells

Nickel oxide (NiO) thin films prepared by cathodic electrodeposition exhibit superior electrical performace than PEDOT:PSS when used as anode interlayers of bulk-heterojunction solar cells. Devices incorporating 30 nm-thick NiO films firstly annealed at 320 °C in air and posteriorly treated with UV-O3 reach power conversion efficiencies comparable to that obtained for PEDOT:PSS-based cells. NiO interlayers enhance contact selectivity by simulataneously increasing shunt resistance (lower leakage current related to electron-blocking ability), and reducing hole-extraction resistance. Carrier selectivity is quantified from the resistance components associated with the impedance response of the anode contacts. The versatile electrodeposition technique of NiO interlayers permits avoiding PEDOT:PSS use as it presents disadvantages related to its acid character and hygroscopic nature.