In recent years, perovskite/crystalline silicon solar cells have become a research hotspot due to their advantages of wide spectral absorption and easy breakthrough of Shockley-Queisser efficiency limit. But, the long-term stability of perovskite materials remains a major challenge.Perovskite materials are very sensitive to environmental conditions,(such as humidity, oxygen and light), and are prone to degradation. This will lead to a rapid decline in the efficiency of the cell, affecting its practical application.

In response to this test demand, Millennial Damp Heat Test Chamber can simulate high temperature, high humidity, long-term moisture penetration environment, with Millennial PID tester, to evaluate whether the electrical performance of cell and module after PID attenuation meets the standard, helping users to provide strong support in improving the efficiency of cell and module.

Development of Perovskite /Crystalline Silicon Tandem Solar Cells

In recent years, the commercialization process of perovskite/crystalline silicon tandem solar cells has made unprecedented strides, and one of its significant advantages lies in the fact that it can be integrated with highly mature commercial crystalline silicon cell production lines. The tandem cell consists of multiple subcells with distinct band gaps, where the wide bandgap top cell absorbs short-wavelength sunlight and the narrow bandgap bottom cell absorbs long-wavelength sunlight. This can effectively broaden the scope of solar spectrum utilization and enhance the photovoltaic conversion efficiency of solar cells.

Table. The latest perovskite/crystalline silicon tandem solar cell 2T, 4T series structure efficiency record  

*The above data is derived in part from NREL and Martin Green Solar Cell Efficiency Tables (64th edition).

Although the 2T and 4T series structures show ultra-high energy conversion efficiency, due to the inherent chemical properties and device structure of perovskite (PVK) materials themselves, their stability is often less than that of crystalline silicon cells.

External Factors Affecting The Stability Of Perovskite (PVK)

With the influence of environmental factors such as moisture, oxygen and light, the external instability of perovskite can have negative effect on the efficiency of perovskite/crystalline silicon tandem cells.

The main causes of external instability of perovskite/crystalline silicon tandem cells and the degradation mechanism of perovskite cell.

In actual reliability tests, it was found that the crystal structure of perovskite PVK remained highly sensitive to temperature, humidity and ultraviolet light, mainly due to the presence of unstable organic cations and the degradation of perovskite PVK materials caused by external factors such as water, light and oxygen.

As an external influencing factor, water has always been considered to be the most harmful factor affecting the stability of perovskite. Perovskite preparation is usually carried out in inert-gas protected glove boxes because the water oxygen molecules in the air can accelerate the degradation of perovskite materials. At the same time, due to the ionic properties of perovskite materials, they can be relatively easily dissolved in polar solvents such as water. Therefore, perovskite materials have obvious moisture instability. Humidity instability can be effectively solved by packaging. However, the perovskite/crystalline silicon tandem solar cells and module manufacturing process can also be affected by humidity.

Due to the degradation of organic substances in perovskites, such as A-site cations in the PVK absorption layer and organic charge transfer materials (spiro-OMeTAD, PCBM and PEDOT:PSS), the performance of PSC decreases at high temperatures. Therefore, defects in PVK, interface characteristics, and packaging techniques all affect the thermal stability of PSC. In practical outdoor applications, solar cells are required to work continuously at temperatures above 60℃, so the thermal stability of perovskite materials in perovskite/crystalline silicon solar cells is crucial to the long-term stability of the cell.

Therefore, in the process of the rapid development of the commercial entry of perovskite/crystalline silicon tandem solar cells, it is necessary to pay attention to the stability test of the product to verify whether it meets the commercial application standards.

And for perovskite/crystalline silicon laminated solar cells, it is very important to consider the different degradation mechanisms and environmental sensitive factors of crystalline silicon cells and perovskite cells, which means that the implementation of reliability testing must be carefully selected at the same time the appropriate aging strategy to fully investigate the degradation of the cell.

Stability test of perovskite/crystalline silicon tandem solar cells

Up to now, there have been a lot of studies on the instability test of single-junction perovskite batteries, but the relevant tests for perovskite series batteries are still few, and usually only focus on some external factors such as time, temperature, humidity, etc. Research on practical test scenarios such as damp heat, ultraviolet light, potential-induced attenuation (PID) and mechanical loads is still lacking.

Taking the photovoltaic device reliability test standards of crystalline silicon solar cells (IEC61215 standard and IEC61730 standard) as an example, respectively from the perspective of component application safety and service life, the test means and test combination sequence are listed, which are the two most important types of standards in all reliability tests.

Combined with the two standards and the external factors that influence the stability of perovskite (PVK) mentioned above, it can be expected that in the stability test of perovskite/crystalline silicon solar cells, the wet-thermal test and ultraviolet durability test are essential test links.

In these two tests, the electrode of the battery will produce a potentially-induced attenuation effect( Potential Induced Degradation ,PID), and due to the series characteristics of the laminated battery, the open circuit voltage of the device is usually close to the sum of the open circuit voltage of the perovskite battery and the crystalline silicon battery, which will lead to more serious PID effect. Therefore, understanding the PID action mechanism and attenuation effect of laminated batteries is also a key research direction.

Millennial Damp Heat Test Chamber

E-mail: market@millennialsolar.com

Photovoltaic module application process will withstand a variety of harsh weather tests. The component's ability to withstand high temperature、high humidity, long-term moisture penetration and other properties need to be evaluated. In order to simulate the high temperature and high humidity environment test, verify and evaluate the reliability of components or materials,Millennial Damp Heat Test Chambe ME-PV-DH9500 was born.

●Ultra-high operating stability for 1000 hours at (85±2)℃ and (85±5)%RH.

●Built-in circulating air duct and long-axis fan for effective heat exchange, the internal temperature of the environmental box is uniform and stable.

●Adopt imported temperature controller, realize multi-stage temperature programming, high precision, good reliability.

●High and low temperature interaction tests can be carried out according to the plan of the engineer.

●It can be paired with Millennial PID Tester for more direct observation of component performance.

Millennial PID Tester

E-mail: market@millennialsolar.com

Millennial PID Tester can communicate with the environment box, through the simulation experiment battery, components in the harsh environment (high temperature, high humidity, high salinity) PID attenuation for a long time to evaluate the electrical performance of the module can meet the requirements.

●Advantech's high-quality industrial computer is used to ensure long-term stable operation of the equipment.

●High precision forward and reverse switching DC power supply.

●Real-time monitoring of voltage,leakage current, insulation resistance curve.

For perovskite/crystalline silicon tandem solar cells, the stability of perovskite materials is an important factor limiting their working life, and also an influential factor hindering the commercialization process. In order to improve and refine the stability measurement standards and processes, it is necessary for the industry to work together to research goals and point the way to improve the efficiency of solar cells.