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 C 60, 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 cm 2. By means of X-ray diffraction (XRD) analysis we show that under continuous operating conditions the source materials possess long-term stability. The CuPc, C 60 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 C 60 layers deposited under conditions appropriate for the preparation of organic solar cells show spectra typical for these materials. Mixed CuPc:C 60 layers with controlled constituent ratios and layer thickness are deposited for the preparation of organic solar cells. First ITO/CuPc:C 60/Al organic photovoltaic devices are prepared with an efficiency of ∼1% (conditions AM1.5).