Boosting solar cell energy capture efficiency with a fullerene-derivative interlayer

Newswise — Solar cells are very important for using renewable energy, and it's useful if they can capture more power from sunlight. Perovskite solar cells are a type of solar cell that can do this, but they are not very stable and don't capture as much power as we would like. Scientists have found a way to improve perovskite solar cells by adding a special layer that makes them more stable and efficient at capturing power from sunlight.

All-inorganic perovskite solar cells are more stable at high temperatures, which is important for their long-term performance. However, they are not as efficient at converting sunlight into electricity compared to solar cells made with a mix of organic and inorganic materials. A group of top scientists who study materials recently explored the use of an additional layer to fix the issues found in all-inorganic perovskite solar cells. In these solar cells, the layers of a material called perovskite, which conducts energy when exposed to light, can have problems with their structure, energy levels, and electron traps. These issues reduce the movement of electrons and overall efficiency of the solar cell. To address these problems, the scientists introduced an extra layer called bis-dimethylamino-functionalized fullerene derivative (PCBDMAM) between the perovskite layer and the layer that helps with electron transport. This interlayer improves the movement of electrons and increases the solar cell's efficiency, while also enhancing its stability at different temperatures.

The team published their findings in the May, 16 issue of Nano Research Energy, published by Tsinghua University Press.

According to Professor Shangfeng Yang, high-efficiency perovskite solar cell devices mostly use a mix of organic and inorganic materials. However, these materials are not very stable when it comes to heat because of certain components they contain. This lack of stability makes it difficult to use these hybrid perovskite solar cells on a large scale.

To make all-inorganic perovskite solar cells more efficient, researchers have been working on a technique called interface engineering. This technique involves improving the arrangement of different layers in the solar cell to make it better at moving electrons. By making adjustments to the structure and properties of the solar cell's layers, researchers have been able to improve its efficiency.

According to Professor Shangfeng Yang, researchers have been using various types of interlayers to improve the performance of all-inorganic perovskite solar cells. These interlayers can be made of small molecules, polymers, inorganic compounds, 2D perovskite layers, fullerene, and its derivatives. They help in addressing defects in the all-inorganic perovskite layer.

In their study, the team specifically used an interlayer called PCBDMAM between an all-inorganic perovskite layer and a zinc oxide electron transport layer. The PCBDMAM was applied as a conductive coating on the zinc oxide surface using a spin-coating technique. This helped to improve the structure and quality of the all-inorganic perovskite layer, as well as enhance the thermal stability of both the zinc oxide and perovskite layers. As a result, the power conversion efficiency (PCE) of the solar cell increased from 15.44% to 17.04%.

To successfully shift to renewable energy, it's crucial to have strong solar cells that can effectively convert sunlight into electricity and endure harsh environmental conditions. One of the main obstacles faced by researchers and material scientists is a phenomenon called direct recombination, which hampers the efficiency of solar cells.

Direct recombination occurs when electrons, generated by sunlight in the solar cell, collide with holes (absence of electrons) and recombine. This recombination process emits a photon of light, which essentially reverses the electricity generation within the solar cell. In simpler terms, direct recombination reduces the amount of electricity that can be produced by the solar cell.

The research team is committed to overcoming obstacles and enhancing the performance and durability of solar cells, aiming to make solar energy production more dependable and cost-effective. Their future focus includes finding ways to address solar cell defects like direct recombination. They plan to achieve this by modifying the composition, concentration, and application of the different layers in solar cells. The goal is to optimize temperature stability and efficiency in a manner that is commercially viable and cost-efficient. By tackling these challenges, the team aims to advance the technology and make solar energy an even more reliable and affordable source of power.

In addition to Shangfeng Yang, other researchers have contributed to this work. Yanbo Shang, Pu Wang, Lingbo Jia, Xingcheng Li, Weitao Lian, Peisan Qian, Tao Chen, and Yalin Lu are from the CAS Key Laboratory of Materials for Energy Conversion in the Anhui Laboratory of Advanced Photon Science and Technology at the University of Science and Technology of China in Hefei, China. Muqing Chen is affiliated with the School of Environment and Civil Engineering at Dongguan University of Technology in Dongguan, China. These researchers have played important roles in advancing the understanding and development of solar cell technologies.

This work was supported by the National Natural Science Foundation of China (51925206, U1932214, 52172053).

##