Undoped tin dioxide transparent electrodes for efficient and cost-effective indoor organic photovoltaics (SnO2 electrode for indoor organic photovoltaics)

Abstract

Indoor organic photovoltaics (OPVs) are currently being investigated for small-scale energy generation from artificial light sources to power small electronic devices. Despite recent progress in increasing the power conversion efficiency (PCE) of indoor OPVs, the widespread use of expensive indium tin oxide (ITO) as a transparent conducting electrode (TCE) leads to long energy payback times. This study provides a novel and comprehensive description of lowtemperature atomic layer deposition (ALD)-processed indium-free tin dioxide (SnO2) films as inexpensive and efficient TCEs for indoor OPVs. These highly conformal and defect-free ALD-fabricated SnO2 films are applied to a poly(3-hexylthiophene):indene-C-60 bisadduct-based OPV system. Under 1 sun illumination, an OPV with an SnO2 TCE exhibits limited operational capacity because of the high sheet resistance (similar to 98 Omega sq(-1)) of the SnO2 layers. However, under a light-emitting diode (LED) lamp with a luminance of 1000 lx, the series resistance, which is related to the sheet resistance, has a marginal effect on the performance of the indoor OPV system, showing a PCE of 14.6 +/- 0.3%. A reference OPV with an ITO TCE has a slightly lower PCE of 13.3 +/- 0.8% under the same LED conditions. These results suggest that SnO2 TCEs can be efficient and cost-effective replacements for ITO TCEs in indoor OPV systems.