Abstract
We demonstrate hybrid organic photovoltaic (HOPV) bilayer devices with very high open circuit voltages (VOC) of 1.18 V based on a sol-gel processed zinc oxide (ZnO) acceptor and a vacuum deposited boron subphthalocyanine chloride (SubPc) donor layer. X-ray photoelectron spectroscopy (XPS) and Kelvin Probe (KP) measurements of the ZnO/SubPc interface show that the ZnO preparation conditions have a significant impact on the film composition and the electronic properties of the interface, in particular the work function and interface gap energy. Low temperature processing at 120 °C resulted in a ZnO work function of 3.20 eV and the highest VOC of 1.18 V, a consequence of the increased interface gap energy.
Highlights
The field of organic photovoltaics (OPVs) has attracted considerable attention due to its potential for low cost solar energy conversion and its compatibility with non-rigid substrates
We show how the combination of a sol–gel processed zinc oxide (ZnO) layer with the small molecule organic semiconductor, boron subphthalocyanine chloride (SubPc), results in planar bilayer hybrid organic photovoltaic (HOPV) cells demonstrating very high open-circuit voltages
X-ray photoelectron spectroscopy (XPS) and Kelvin Probe (KP) measurements of the ZnO/SubPc interface show that the ZnO preparation conditions have a significant impact on the composition of the layers and the electronic properties of the interface, most notably the work function and interface gap energy, and careful optimisation leads to a high VOC of 1.18 V and a respectable power conversion efficiency (PCE) of 0.47%, values much higher than those previously reported for similar device architectures
Summary
The field of organic photovoltaics (OPVs) has attracted considerable attention due to its potential for low cost solar energy conversion and its compatibility with non-rigid substrates. In a simple bilayer device with the polymeric donor poly(3-hexylthiophene) (P3HT), the VOC was increased from 0.4 V to 0.6 V by replacing the ZnO sol–gel layer with ZnO nanoparticles This was attributed to the increase in ZnO band gap resulting in a larger Ig. The substitution of polymers in HOPVs with evaporated organic small molecule semiconductors is an area that has received very little attention.[24,25] One particular benefit is that it allows the controlled growth of very thin layers of the organic material, allowing the interface properties to be probed in a much more systematic way in order to explore the impact of the inorganic/organic junction on device performance. X-ray photoelectron spectroscopy (XPS) and Kelvin Probe (KP) measurements of the ZnO/SubPc interface show that the ZnO preparation conditions have a significant impact on the composition of the layers and the electronic properties of the interface, most notably the work function and interface gap energy, and careful optimisation leads to a high VOC of 1.18 V and a respectable PCE of 0.47%, values much higher than those previously reported for similar device architectures
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