| Work Detail |
Developed by Chinese scientists, the solar cell has achieved the highest open circuit voltage ever recorded in an inverted perovskite photovoltaic device. The lead carbanion layer was responsible for reducing defects at the interface between the perovskite layer and the electron transport layer.
A group of researchers led by NingboTech University in China has fabricated an inverted perovskite solar cell with a lead carbanion (Pb-C-)-based interface passivator.
Inverted perovskite cells have a device structure known as a "pin," in which the p-hole selective contact is on the bottom of the intrinsic perovskite layer i and the n-electron transport layer on top. Conventional halide perovskite cells have the same structure but inverted: a "nip" arrangement. In the nip architecture, the solar cell is illuminated through the electron transport layer (ETL) side; in the pin structure, it is illuminated through the hole transport layer (HTL) surface.
Inverted perovskite solar cells are known for their impressive stability, but have been held back by their lower efficiency in converting sunlight into electricity. This problem arises primarily at the point where the perovskite layer meets the electron transport layer, resulting in energy loss rather than conversion into useful energy. The energy loss is primarily due to carrier recombination, particularly at the interface between the perovskite and the electron transport layer.
“Lead carbanion complexes are one of the least explored and understood carbon complex species and have so far only been observed in the liquid phase,” Zhenhua Xu, lead author of the research, told pv magazine . “In our work, we present the synthesis of bulk lead carbanion complexes and aim to explore their influence on the photoelectric properties of perovskite solar cells.”
In the study “ Lead carbanion anchoring for surface passivation to boost efficiency of inverted perovskite solar cells to over 25%” recently published in the Chemical Engineering Journal , the scientists explained that upon carbanion treatment, the residual lead cation (Pb2+) at the interface could be completely neutralized and coordinated.
“A comprehensive investigation of the properties of perovskite films, using photoluminescence (PL) mapping and scanning electron microscope (SEM) imaging, revealed that carbanion passivation reduces defect-rich domains and decreases grain isolation on the perovskite surface,” Xu said.
The group constructed the solar cell with an indium tin oxide (ITO) substrate, a self-assembled monolayer (SAM) as HTL, the perovskite absorber, the Pb-C- passivator, an ETL based on phenyl-C61-butyric acid methyl ester (PCBM), a bathocuproine (BCP) buffer layer, and a silver (Ag) metal contact.
Tested under standard lighting conditions, the device efficiency reached 25.16%, an open-circuit voltage of 1.17 V, a short-circuit current density of 25.30 mA/cm2 and a fill factor of 85.0%. “This good performance is mainly attributed to a high open-circuit voltage of 1.17 V and a minimum voltage loss of 0.38 V,” Xu explained, adding that the cell achieved the highest open-circuit voltage ever recorded in an inverted perovskite PV device. “The perovskite surface was anchored by a strong Pb-C- bond, resulting in a stable device with a lifetime of more than 3 months.”
Looking ahead, the research group plans to investigate other lead carbanion complexes with different cations, with which it hopes to synthesize more crystals and find applications beyond photovoltaic solar energy. |
