Degradation mechanism of organic photovoltaic devices with bathocuproine buffer layer

Abstract

Thedegradation mechanism of pentacene/fullerene (C60)-based photovoltaic device is studied asa function of heating time. The efficiency of the devicewith bathocuproine (BCP) as buffer layer shows a considerable decayfrom 1.49 to 0.6% after 168-h heating, whereas the devicewithout BCP possessed a stable performance under heating treatment. Thisdecay is mainly caused by the poor thermal stability ofBCP, which crystallized after the heating treatment and is discussedthrough the incident photon-to-electron conversion efficiency (IPCE) and the atomicforce microscopic (AFM) measurements. The IPCE results indicated the redistributionof optical field due to the crystallization of BCP, andthe AFM images showed the significant increase in surface root-mean-squarevalue from 0.46 to 24.7 nm. Furthermore, the device withoutBCP exhibited the decrease in series resistance (Rs). The reducedRs was attributed to the polycrystallized-like molecular arrangement after heating,which was confirmed by the Gaussian-disordered model. ©2011 Society of Photo-Optical Instrumentation Engineers (SPIE)