Lifetime analysis and degradation study of OPVs utilising a solution processed V2O5 Intelayer

Alastair Buckley^a, David Lidzey^a, Abullah Alsulami^a

^aUniversity of Sheffield, Hounsfield Road, United Kingdom

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics 2015 (HOPV15)

Roma, Italy, 2015 May 11th - 13th

Organizer: Filippo De Angelis

Poster, Abullah Alsulami, 070
Publication date: 5th February 2015

The environmental stability and lifetime of photovoltaic devices is a prime concern, particularly in the research of organic photovoltaic (OPV) technologies. Here we investigate the interface effects of solution processed vanadium oxide (s-V₂O_x) as hole transport layer (HTL) on OPV device lifetime using a number of techniques. The lifetime of s-V₂O_x devices are compared with that of the most widely used HTLs, PEDOT:PSS and thermal evaporated MoO3. In recent years, several studies have shown that fabrication OPVs with s-V₂O_x exhibit high performance which are similar or better than other devices that utilise different HTLs. However, most of aqueous metal oxides reported in literature require post-deposition treatment such as thermal annealing and plasma treatment. Herein we fabricated V₂O_x thin films (4 nm thickness) by a spin-coating solutions of vanadium oxitriisopropoxide precursor at room temperature in air without any post-annealing or plasma treatment. OPVs incorporating untreated s-V₂O_xthin film and active layer of PFD2TBT8:PC70BM shows efficiency up to 6.5 %. This is comparable to devices made with a thermally evaporated MoOx or PEDOT:PSS HTL. Preliminary lifetime results of OPVs made with various HTLs reveal that devices incorporation untreated s-V₂O_x have the shortest lifetime. Applying the thermal annealing process or increasing V₂O_x layer thickness up to 20 nm can improve significantly the lifetime. Although the initial I-V characterisation of devices with untreated 20 nm thickness shows low photovoltaic parameters, their lifetime data exhibit significant improvement to be comparable with other devices. Moreover, V₂O_x layers annealed at 130

in air for 30 minutes show obviously less degradation than unannealed devices. The laser-beam-induced photocurrent (LBIC) and scanning electron microscope (SEM) of fresh and aged OPVs with different HTLs has also been used to investigate the degradation mechanism and poor device lifetimes.

Further investigation has been carried out by intensity- modulated spectroscopy (IMS) technique that has been designed and developed by our group.
The J–V characteristics of fresh and aged OPVs with different hole transport layer.
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