Comparison of organic photovoltaic with graphene oxide cathode and anode buffer layers Abd. Rashid Bin Mohd Yusoff ⇑ , Hyeong Pil Kim, Jin Jang Department of Information Display and Advanced Display Research Center, Kyung Hee University, Dongdaemun-ku, Seoul 130-171, Republic of Korea article info Article history: Received 5 June 2012 Received in revised form 3 July 2012 Accepted 16 July 2012 Available online 1 August 2012 Keywords: Photovoltaic Inverted photovoltaic Aluminum doped zinc oxide Graphene oxide abstract In this report, we present inverted organic solar cells integrating solution-processed alumi- num doped zinc oxide (AZO) and trilayer graphene oxide (GO) as an electron selective and anode buffer layers, respectively. The polymers in this inverted architecture are PCDTBT, PBDTTPD and PCBM as an electron donor and acceptor, respectively and the photovoltaic performance were recorded at 300 K under 100 mW/cm 2 light intensity. The characteristics of PCDTBT and PBDTTPD-based inverted solar cells were: open-circuit voltages (V oc ’s) 0.74 and 0.70 V, short-circuit current densities (J sc ’s) 12.09 and 12.06 mA/cm 2 , fill factors (FFs) of 60.73% and 60.03%, with an overall power conversion efficiencies (PCEs) of about 5.46% and 5.07%. The fabricated inverted cells show better performances compared to con- ventional structure reference cells. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Today, organic photovoltaics (OPVs) have received numerous attentions as an alternative energy device due to its various advantages namely low manufacturing cost, low temperature, easiness in fabrication procedure, and compatible with roll-to-roll method. However, one major drawback of OPVs is low power conversion efficiency (PCE). Although the PCE is improving during these years but, it is still insufficient to be commercialized. As gener- ally accepted, and before OPVs can be commercialized, a numbers of processing, stability and life time issues must be taken into serious consideration. Hence, in order to en- hance the PCE, copious works have been reported. Signifi- cant amount of research works have reported for electron extraction layers namely titania (TiO x ), gallium doped zinc oxide (GZO), and zinc oxide (ZnO) [1–11]. There are also a lot of reported works on hole extraction layers such as graphene oxide (GO), nickel oxide (NiO x ), cesium carbonate (CsCo 3 ), molybdenum oxide (MoO 3 ), and tungsten oxide (WO 3 ) [12–15]. Recently, Fan et al. reported inverted solar cell based on flake-like aluminum doped zinc oxide nano- structure. In their work, by means of doping and varying Al concentrations, they managed to tune the electrical con- ductivity, and morphology of the AZO thin films leading to a significant improvement in PCE of about 58.7% com- pared to that of ZnO-based inverted solar cells [16]. For that reason, in the present work, we have studied the hy- brid organic–inorganic OPVs using a solution processed AZO as an inorganic electron buffer layer, graphene oxide (GO) as inorganic hole buffer layer, and PCDTBT and PBDTTPD as organic donors. These OPVs structure offer a few advantages such as the presence of GO, and the ab- sence of PEDOT:PSS, which can alleviate a degradation pro- cess, and at the same time avoiding the presence of ITO/ PEDOT:PSS interface. In the present study, the effect of the photoactive layer on the performance of OPVs was investigated. The inverted OPVs show excellent performances with the efficiencies more than 5% while the conventional OPVs only demon- strated efficiencies around 2.81%. This new structure not only employing a low band-gap materials but also avoiding 1566-1199/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.orgel.2012.07.024 ⇑ Corresponding author. Tel.: +82 2 961 0270; fax: +82 2 961 9154. E-mail addresses: abd@tftlcd.khu.ac.kr (A.R.B. Mohd Yusoff), jjang@ khu.ac.kr (J. Jang). Organic Electronics 13 (2012) 2379–2385 Contents lists available at SciVerse ScienceDirect Organic Electronics journal homepage: www.elsevier.com/locate/orgel