Enhanced cell performance by controlling the surface morphology of ZnO buffer layers in organic photovoltaic cells. (October 2015)

• Record Type: Journal Article
• Authors: Oh, Seho; Kang, Taeho; Oh, Seong-Geun
• Is Part Of: Solar energy. Volume 120(2015)
• Page Start: 363
• Page End: 369
• Publication Date: 2015-10
• Subjects: Organic solar cell -- Buffer layer -- Surface morphology -- Zinc oxide nanoparticles; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2015.07.047
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: Colloidal solutions of spherical and rod-shaped ZnO nanoparticles were prepared by sol–gel method. Four types of thin film were fabricated with those ZnO colloidal solutions as the buffer layer in OPVs. Surface morphology of ZnO films was varied depending upon the type of ZnO colloidal solutions. Best PCE of OPV was obtained with the most rough and highest surface area of ZnO films. Abstract: Thin layer of ZnO with mixture of spherical and rod-shaped nanoparticles (NM) was prepared as the buffer layer in inverted organic photovoltaic cells (OPVs). The spherical and rod-shaped ZnO nanoparticles were synthesized through sol–gel method to investigate the effect on surface area of ZnO buffer layer. The prepared samples were made up of a 50/50 wt.% mixture of spherical ZnO and rod-shaped ZnO nanoparticles. The surface area of ZnO thin layer prepared with mixture of spherical and rod-shaped nanoparticles has the higher specific surface area than that of ZnO film prepared with spherical or rod-shaped nanoparticles, respectively. The high surface area in buffer layer induced the fast electron transfer in OPVs. Also, the sample NM has the rough surface structure due to the morphology of mixed ZnO nanoparticles. The rough structure increased the contact area at the interface (ZnO buffer layer/active layer). Due to these two reasons, the series resistance ( R s ) of the device was decreased. By reduction of the R s, the current density ( J sc ) and fill factor (FF) of device were improved. The highest power conversion efficiency (PCE) with NM is achieved for 2.75% under 100 mW/cm 2 at AM 1.5 G simulated solar emission.