ELECTRICAL CHARACTERIZATION OF PEROVSKITE AND ORGANIC electronics

Introduction

The past decade witnessed an impressive development in power conversion efficiencies of novel thin film solar cells based on organic materials, quantum dots, hybrid and perovskite materials. All these new concepts are denoted by the term ‘third generation photovoltaics’ and have in common that the variety of possible materials and device structures is very large. Accurate characterization is therefore crucial for material screening and device optimization. Developing a physical understanding of mechanisms governing the operation of third-generation solar cells is much more demanding than for silicon solar cells. In contrast to crystalline silicon, photogeneration and transport of charges in third-generation solar cells are more difficult to understand and requires more complex characterization techniques.

There are numerous experimental techniques available to study electrical material and device parameters of solar cells. In this review, we aim to give an overview of some of the most prominent experimental techniques. These are all implemented in our opto-electrical characterizaton system Paios.

1- Current-Voltage Characteristics

The IV-curve is the default characterization technique for solar cells. The standard solar cell parameters short-circuit current, open-circuit voltage, fillfactor and maximum power are automatically calculated. The fastest version of this measurement is the ramped IV. For more precise measurements of very low currents or to investigate the equilibration time this measurement type is also available as sequential and pulsed IV.

Analysed Parameters:

MPP, FF, Voc, Isc, SCLC mobility, Single Diode Model, Dark and Light Ideality factor.

Fig. 1. I-V characteristics of an organic solar cells at different light intensity with respect to 1 sun (100%).

Fig. 1. I-V characteristics of an organic solar cells at different light intensity with respect to 1 sun (100%).

2 - Current-Voltage-Luminance Characteristics

The IVL curve is the default characterization technique for OLEDs. The current-voltage curve is measured as in the normal IV. Additionally, the steady-state emission of the OLED is recorded using a photodetector. Knowing the spectrum of the OLED and the sensitivity/geometry of the photodetector, the electrical and optical efficiency of the OLED can be calculated. The fastest version of this measurement is the ramped IVL. For more precise measurements of very low currents or to avoid heating of the device the measurement can be perforemd as pulsed IVL.

Analysed Parameters:

Emission Turn-on Voltage, OLED working point, Single Diode Model

Fig 2: current efficiency VS Current density of an organic light emitting diode.

Fig 2: current efficiency VS Current density of an organic light emitting diode.

Transient Photocurrent_TPC.PNG

3 - Transient Photocurrent (TPC) - Current Response to a Light-Pulse

The device is flashed with a light-pulse, charges are generated and the transient photocurrent is measured at short-circuit or with an offset voltage applied. This experiment can also be performed in the small-charge limit with bias illumination in order to determine the charge density.

Analysed Parameters:

Electron and hole mobility, trapping dynamics