Performance Breakthrough! Co-adsorption Self-assembly Technology Pushes Efficiency of Inverted Perovskite Solar Cells to Over 24.68%

Scientists from China’s Southern University of Science and Technology, Hong Kong Polytechnic University, and the Chinese University of Hong Kong have published a paper in Nature Communications titled “Co-adsorbed self-assembled monolayer enables high-performance perovskite and organic solar cells”. They have developed an inverted perovskite solar cell based on a hole transport layer (HTL) and self-assembled monolayers (SAM) to reduce passivation defects and improve efficiency, becoming a key to achieving high-performance perovskite solar cells (PSC) and organic solar cells (OSC).

Inverted perovskite cells have a device structure called "p-i-n", in which hole-selective contact p is located at the bottom of the intrinsic perovskite layer i, and the electron transport layer n is located at the top. Conventional halide perovskite cells have the same structure but reversed - a "n-i-p" layout. In the n-i-p architecture, solar cells are illuminated through the electron-transport layer (ETL) side; In the p-i-n structure, it is illuminated through the HTL surface.

from the research team's paper

In this study, researchers proposed a co adsorption (CA) strategy to introduce a novel small molecule, 2-chloro-5- (trifluoromethyl) isonicotinic acid (PyCA-3F), into the buried interface between 2PACz and perovskite/organic layer, effectively reducing the aggregation of 2PACz, improving surface smoothness, and increasing the work function of the modified SAM layer, thereby providing a flat buried interface and favorable heterojunction for perovskite.

In addition, researchers also manufactured organic solar cells based on 2PACz/PYCA-3F to test this method. They used the open-air blade coating method to manufacture p-i-n structured OSC devices, achieving "one of the best results of open-air blade coating" through co adsorption strategy and a novel small molecule acid SAM, improving the stability of perovskite and OSC devices. The team stated, "After 1000 hours of maximum power point tracking, the encapsulated PSCs and OSCs maintained initial efficiencies of approximately 90% and 80%, respectively.

Device performance of PSCs & OSC (from the research team's paper)

The improvement of crystallinity, minimization of trap states, and enhancement of hole extraction and transport capabilities have resulted in a power conversion efficiencies (PCEs) of PSCs with p-i-n structure exceeding 25% (certified as 24.68%).