Chinese researchers develop flexible all-perovskite tandem solar cells with 24.7% efficiency

According to foreign media reports, researchers from Nanjing University, Jilin University, Shanghai Tech University and East China Normal University have launched a new strategy, to develop more efficient solar cells based on flexible perovskites.This strategy bridges perovskite with low-temperature processed NiO nanocrystal thin films by using two hole-selective molecules based on carbazole cores and phosphonic acid anchoring groups.

Image source: Journal "Nature Energy"

The researchers designed flexible all-perovskite tandem solar cells with careful design and composition.When the cell's front-side cell, which consists of a perovskite film with a wide-bandgap, is illuminated by the sun, it absorbs high-energy photons.On the other hand, its rear cells absorb low-energy photons that pass through the front cells.

"Compared with rigid perovskite solar cells, lightweight and flexible all-perovskite tandem solar cells are more cost-effective in terms of transportation, storage and installation," said one of the researchers, Professor Tan Hairen from the School of Modern Engineering and Applied Science, Nanjing University. Attractive for building/vehicle integrated photovoltaics (PV), wearable electronics, portable energy systems, and aerospace applications. Compared with flexible single-junction perovskite solar cells, flexible all-perovskite tandem solar cells can achieve higher s efficiency."

Hairen Tan and colleagues used a mixture of two hole-selective molecules based on carbazole cores and phosphonic acid anchoring groups to form self-assembled monolayers (SAMs).Experiments show that SAM molecules cannot be directly applied to ITO-coated flexible PET substrates in flexible solar cells, as it would lead to severe shunting of solar cells.To overcome this challenge, Hairen Tan and colleagues used NiO nanocrystals to create a hole-transporting layer.

Professor Tan said: "Our new strategy leads to record-breaking flexible solar cells. The experiments also show that mixing two SAMs (2PACz and MeO-2PACz) with different dipole moments can flexibly tune the HTL energy levels, thus enabling the Better energy alignment with the perovskite absorber layer significantly improves hole extraction efficiency."

In initial tests, the researchers designed the solar cell to achieve a remarkable efficiency of 24.7 percent, an efficiency that no other flexible thin-film solar cell has ever achieved before.Hairen Tan and colleagues also showed that carefully designed molecular-based interfaces to bridge the hole transport layer and perovskite thin films can significantly improve the bending durability of solar cells, allowing them to maintain their initial performance over 10,000+ operating cycles, The bending radius is only 15mm.