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High-Performance Inverted Organic Photovoltaics Without Hole-Selective Contact.

ACS applied materials & interfaces (2015-10-16)
Achilleas Savva, Ignasi Burgués-Ceballos, Giannis Papazoglou, Stelios A Choulis
ABSTRACT

A detailed investigation of the functionality of inverted organic photovoltaics (OPVs) using bare Ag contacts as the top electrode is presented. The inverted OPVs without a hole-transporting layer (HTL) exhibit a significant gain in hole-carrier selectivity and power-conversion efficiency (PCE) after exposure in ambient conditions. Inverted OPVs comprised of ITO-ZnO-poly(3-hexylthiophene-2,5-diyl)/phenyl-C61-butyric acid methyl ester (P3HT/PCBM)-Ag demonstrate over 3.5% power conversion efficiency only if the devices are exposed in air for over 4 days. As concluded through a series of measurements, the oxygen presence is essential to obtaining fully operational solar cell devices without HTL. Moreover, accelerated stability tests under damp heat conditions (RH = 85% and T = 65 °C) performed to nonencapsulated OPVs demonstrate that HTL-free inverted OPVs exhibit comparable stability to the reference inverted OPVs. Importantly, it is shown that bare Ag top electrodes can be efficiently used in inverted OPVs using various high-performance polymer-fullerene bulk heterojunction material systems demonstrating 6.5% power-conversion efficiencies.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Ethanolamine, ≥98%
Sigma-Aldrich
2-Methoxyethanol, anhydrous, 99.8%
Sigma-Aldrich
Ethanolamine, ACS reagent, ≥99.0%
Sigma-Aldrich
Ethanolamine, liquid, BioReagent, suitable for cell culture, ≥98%
Sigma-Aldrich
Ethanolamine, purified by redistillation, ≥99.5%
Sigma-Aldrich
Ethanolamine, ≥99%
Sigma-Aldrich
2-Methoxyethanol, ReagentPlus®, ≥99.0%, contains 50 ppm BHT as stabilizer
Sigma-Aldrich
2-Methoxyethanol, contains 50 ppm BHT as stabilizer, ACS reagent, ≥99.3%
SAFC
Ethanolamine