Non-Steady State Operation of Polymer/TiO 2 Photovoltaic Devices
- PDF / 128,679 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 75 Downloads / 208 Views
S3.19.1
Non-Steady State Operation of Polymer/TiO2 Photovoltaic Devices Kiril R. Kirova*, Victor M. Burlakova, Michelle J. Careya, Bernard M. Henrya, Zhibin Xiea, Christopher R. M. Grovenora, Hazel E. Assendera, Graham R. Websterb, G. Andrew D. Briggsa a
Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK Dysons Perrins Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QY, UK
b
Introduction Polymer/TiO2 composite solar cells (CSCs) are currently being investigated by academic research groups and industrial companies due to the prospect of achieving good power conversion efficiencies and lifetime stability at a low production cost. We present data of the initial period of operation (up to several hours) of such devices, which show that during this period the CSCs operate in a non-steady state regime. The transient behaviour is accounted for using an equivalent circuit model (ECM) of the photovoltaic device with time-dependent resistors. Experimental Photovoltaic (PV) devices were formed on pre-patterned ITO/glass in a single layer (ITO/MEH-PPV/Au) and bi-layer (ITO/TiO2/MEH-PPV/Au) configuration. The TiO2 layers were prepared by doctor blading a paste (Solaronix, SA Switzerland). The doctor bladed layers were allowed to dry at 100°C for a few minutes before annealing in air at 450°C in a furnace for 10 hours. MEH-PPV films, ranging from 40 to 60 nm thick, were spin-coated on top of the ITO/glass or onto the TiO2 layers from chlorobenzene solutions at a spin speed of 2000 rpm for 30 seconds. The devices were completed by evaporation of a gold electrode (45 nm thick) at a rate of 20 Å/min in a vacuum of the order of 10-6 Torr. The active area of each device was 0.062 cm2. IV measurements of the photovoltaic devices were carried out both in the dark and under illumination using a Keithley 2400 source meter. The light illumination experiments were performed using a KH Steuernegel 1200 Solar Simulator with or without a 420 nm long-pass filter. The illumination power at the sample position for the solar simulator measurements was 86 and 100 mWcm-2 with and without. All IV experiments were performed in vacuum of 15 mTorr. Time Dependence of Voc and Isc Literature reports on the performance of polymer/TiO2 composite solar cells (CSCs) customarily quote single values for the device parameters: Voc, Isc, fill factor (FF) and power conversion efficiency η. In our experience however, polymer/TiO2 CSCs operate in a nonsteady state regime at the start of illumination. All PV parameters vary with time and the variation is strongest during the first 10-15 minutes of operation. Having tested PV cells of a *
Corresponding author: Telephone: +44-(0)1865-273704, Fax: +44-(0)1865-273789, E-mail: [email protected]
S3.19.2
variety of architectures, e. g. single layer, bi-layer, and the more complex TiO2/polymer:TiO2 hetero-junction/polymer configuration, we can confirm that the variation with time of Voc and Isc can be schematically represented using the generalised curves of Fig
Data Loading...
