Oxygen induced p-doping of α-nickel phthalocyanine vacuum sublimed films: Implication for its use in organic photovoltaics

Abstract

The effects of oxygen doping on the charge transport and photovoltaic properties of ␣-nickel phthalocyanine ͑␣-NiPc͒ based devices are investigated using in situ and ex situ I -V measurements. I -V characteristics for devices employing gold contacts indicate ohmic conduction at low voltages, followed by space-charge-limited conduction in higher fields. Upon exposure of NiPc to dry air an increase in the hole concentration (p 0 ) from 8.5ϫ1010 to 2.6ϫ10 15 m Ϫ3 is observed. When the top gold ohmic cathode is replaced by lead, Schottky type behavior is evident with the junction exhibiting photovoltaic effect. The energy conversion efficiency of the cell increases following exposure to oxygen. These results suggest that fabrication of air stable electronic devices based on NiPc is feasible.

Enhanced cyanine solar cell performance upon oxygen doping (Organic Electronics 9 (2008) 85–94)

“…Rectification of the current-voltage characteristics upon doping with oxygen has indeed been observed in the literature and has been attributed to Schottky barrier formation at the metal electrode [35]. In the present work, p-type doping induced by oxygen would give rise to a Schottky barrier at the anode, favouring hole injection and inhibiting electron injection (Fig.…”

Alternating current conduction properties of thermally evaporated α-nickel phthalocyanine thin films: Effects of oxygen doping and thermal annealing

“…4,9,23 In order to identify whether the effects of O 2 doping are similarly pronounced in the case of ac conductivity, a sample consisting of a 0.4 m thick NiPc layer has been realized. Figure 5 shows a logarithmic plot of versus f for various exposure times to dry air.…”

Hole injection or blocking? The role of CuPc in Alq3-based organic light-emitting devices

“…In organic devices incorporating ITO, it is well known that oxygen can easily diffuse from ITO to the organic layer. The effect of oxygen molecules inside the organic material, especially in phthalocyanine (Pc) family, on the current profile has been reported previously [13,14]. Oxygen has been observed to increase the carrier concentration of CuPc by many orders [14].…”