Double-sided Perovskite Solar Cells, The Next Investment Outlet?

As a representative of the third generation of non-silicon thin-film batteries, perovskite batteries have attracted much attention since their birth. Photovoltaic manufacturers, capital markets, and R&D groups all have great expectations for perovskite solar cells.

 

Compared with the common crystalline silicon solar cells on the market, perovskite solar cells have more than 10 times the light absorption capacity of crystalline silicon, and the conversion efficiency is constantly improving. They are also relatively light and thin, with rich application scenarios and relatively low material manufacturing costs. The disadvantage is that the stability is relatively poor and the service life is relatively short.

 

However, technological innovations and improvements around perovskite are constantly breaking through. Some focus on the mixing of perovskite and crystalline silicon to form stacked solar energy. There are also research teams that have developed double-sided perovskite cells in order to improve efficiency.

 

A few days ago, a research team at the US Department of Energy's National Renewable Energy Laboratory (NREL) claimed that their newly developed double-sided perovskite solar cells achieved 91%-93% facility.

 

According to the experimental study, double-sided perovskite cells have the potential to produce 20 percent more electricity than single-sided perovskite cells.

 

The study, titled "High-Efficiency Bifacial Single-Junction Perovskite Solar Cells," was published in the journal Joule.

 

01

Receiving reflected light on the back is close to the front efficiency

 

The so-called double-sided perovskite solar cell, as the name suggests, means that both sides can capture sunlight to generate electricity, and the sunlight captured on the back mainly comes from the reflected light below the module.

 

Will the efficiency be greatly reduced by absorbing reflected light?

 

The efficiency of single-sided solar cells has reached a record high of 26%. This time, NREL claimed that the efficiency of their reverse side is 91-93% of that of the front side, and the efficiency of the reverse side can reach about 24%. The effect is still very good.

 

Researchers say they have engineered a double-sided perovskite solar cell with a modified thickness that achieves very close efficiencies under double-sided illumination. They used optical and electrical simulations to determine the thickness needed for the battery.

 

To absorb most of the photons in certain parts of the solar spectrum, the perovskite layer on the front side of the bifacial solar cell must be thick enough, but not so thick that it blocks the photons. The team also determined the ideal thickness of the back electrode to minimize resistive losses.

 

Guided by the simulated values, the research team designed bifacial cells with a precise thickness of 850 nanometers. That's much less than the thickness of human hair, which is about 70,000 nanometers thick.

 

The researchers placed the cell between two solar simulators to evaluate the efficiency achieved by double-sided illumination. Direct light is aimed at the front, while the back receives reflected light. The efficiency of perovskite cells increases as the ratio of reflected light to front-illuminated light increases.

 

02

Double-sided perovskites are more economical

 

NREL says the goal for bifacial perovskite cells is to achieve front-side efficiencies on par with single-side efficiencies, which have been published for a variety of commercial cells, such as 28.6% for Oxford PV, while rear-side efficiencies are very close to these levels. In the test cells, the front-side conversion efficiency was 23%, and the back-side conversion efficiency was 91-93% of the front-side efficiency.

 

"This perovskite cell can operate very efficiently on either side," said Kai Zhu, a senior scientist at NREL's Center for Chemistry and Nanoscience.

 

He added that although the production cost is higher than that of single-sided cells, in the long run, the power generation of double-sided perovskites can be 10-20% higher than that of single-sided cells, proving that double-sided perovskites are more economical.

 

The NREL research, funded by the U.S. Department of Energy's Office of Solar Energy Technologies, is currently in the hypothetical stage.

Currently, single-sided perovskite cells are not yet in mass production, let alone bifacial cells. The industry believes that perovskites may enter the solar PV market, starting with rooftops and small-scale projects. In these projects, high efficiency is more critical than installation cost, and this requires the innovation of myofascial technology in the first place. Right now, that's a major concern for those looking to bring this technology to market.

 

However, double-sided solar energy is a direction that the scientific research community is constantly exploring.

 

Earlier, the Netherlands Energy Research Center (ECN) announced that it has successfully developed a double-sided tandem perovskite solar cell with an efficiency of up to 30.2%, which is one-third higher than the efficiency of conventional solar cells (about 20%-22%).

 

The cell adopts perovskite thin film technology, crystalline silicon technology, and double-sided silicon technology. In addition to absorbing sunlight on the front side to generate electricity, the back side can also receive scattered light and reflected light from the environment to generate electricity. Therefore, it has a higher comprehensive power generation efficiency. It successfully broke through the limit of single-sided solar cells and achieved a high photoelectric conversion efficiency of 30.2%.

 

In China, there are already use cases for bifacial crystalline silicon solar energy. 1 million-kilowatt "salt-solar complementary" photovoltaic project uses double-sided solar energy. The "salt-light complementary" power station has added a double-sided power generation design. Not only the upward side of the photovoltaic panel can directly convert electric energy, but the back can also absorb sunlight reflected from the water surface, which can increase the power generation efficiency of the photovoltaic power station by 5%-7%.