Organic donor, acceptor and buffer layers of small molecules prepared by OVPD technique for photovoltaics

Abstract

Organic vapour-phase deposition (OVPD®) is used for the growth of the organic solar cell component materials such as the donor copper phthalocyanine (CuPc), the acceptor fullerene C60, and electron-conducting buffer layers of bathocuproine (BCP) on Si〈1 0 0〉 wafers and indium tin oxide (ITO) substrates on areas as large as 15×15 cm2. By means of X-ray diffraction (XRD) analysis we show that under continuous operating conditions the source materials possess long-term stability. The CuPc, C60 and BCP thin film morphology and structure are characterised using scanning electron microscopy and XRD analysis. We demonstrate CuPc thin films with a highly folded surface morphology suitable for the preparation of solar cells with an interpenetrating donor-acceptor interface. The XRD diffraction patterns of the CuPc and C60 layers deposited under conditions appropriate for the preparation of organic solar cells show spectra typical for these materials. Mixed CuPc:C60 layers with controlled constituent ratios and layer thickness are deposited for the preparation of organic solar cells. First ITO/CuPc:C60/Al organic photovoltaic devices are prepared with an efficiency of ∼1% (conditions AM1.5). © 2007 Elsevier Ltd. All rights reserved.