RSoft Application Gallery Note: Multi-Junction Organic Solar Cells

Structure Overview

This multi-junction solar cell consists of three organic cells, each consisting of a CuPc and a PTCBI region (red and blue regions in Fig. 1). The cells are separated by a thin silver layer that acts as a combination area for electrons. The Ag layers do not contribute greatly to the optical performance of the device, but are included here for completeness. Two layers are placed on the front of the device: a SiO2 substrate layer and an ITO layer. A silver layer is placed on the back of the device to act as a reflector.

The incident sunlight is a plane wave and launched from air into the bottom of the structure shown below in Figure. 1

 multi-junction organic solar cell

Figure 1: The multi-junction organic solar cell as seen in the RSoft CAD Environment
interface. As drawn here, the light is incident from the bottom of the structure.

Computing Solar Cell Performance

The Solar Cell Efficiency can be easily computed using RSoft's Solar Cell Utility™. Here, we use RSoft's MOST™ scanning tool to compute the Solar Cell Efficiency at three different incident light intensities; 10, 100, and 1000 (mW/cm2).

Solar Cell Efficiency (%) of the structure

Figure 2: Solar Cell Efficiency (%) of the structure shown in Fig 1. This plot corresponds to Fig 3 in Ref [1].
An incident light intensity of (10,100,1000) [mW/cm2] corresponds to Structure_num=(1,2,3).

Several settings used by the Solar Cell Utility in computing the Solar Cell Efficiency (%) include the Global Collection Efficiency, the Open Circuit Voltage, and the Filling Factor.

  • The Global Collection Efficiency (GCE) represents the efficiency at which generated electron-hole pairs are captured by the electrodes within the device. There are generally two methods to compute this quantity: 1) Perform a complete electronic simulation via RSoft's LaserMOD™ simulation tool, or 2) Fit the simulation results found with the Ideal Diode electronic model to experimental data. Here, we have used the Ideal Diode model utilizing the experimental data in Ref [1] to compute the GCE.
  • For this application note, the values for the Open Circuit Voltage and Filling Factor were obtained directly from Ref [1].

 

The Solar Cell Efficiency results at varying incident light intensities, as shown in Fig 2, agree well with Fig 3 in [1]. For a more detailed study of this structure, it would be necessary to use the LaserMOD electrical model.

References:

[1] A Yakimov, et al, "High photovoltage multiple-heterojunction organic solar cells incorporating interfacial metallic nanoclusters" Appl. Phys. Letters, 80 1667-1669 (2002)