| Work Detail |
Developed by Scientists in China, the solar cell reportedly achieved the highest open-circuit voltage ever recorded for an inverted perovksite PV device. The lead carbanion layer was responsible for reducing defects at the interface bewteen the perovskite layer and the electron transport layer.
A group of researchers led by the NingboTech University in China has fabricated an inverted perovskite solar cell with an interface passivator based on lead carbanion (Pb–C–).
Inverted perovskite cells have a device structure known as “p-i-n”, in which hole-selective contact p is at the bottom of intrinsic perovskite layer i with electron transport layer n at the top. Conventional halide perovskite cells have the same structure but reversed – a “n-i-p” layout. In n-i-p architecture, the solar cell is illuminated through the electron-transport layer (ETL) side; in the p-i-n 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 lower efficiency in turning sunlight into electricity. This issue mainly arises at the point where the perovskite layer meets the electron transport layer, causing energy loss instead of being converted into useful power. The energy loss is primarily caused by carrier recombination, especially at the interface between perovskite and the electron transport layer.
“Lead carbanion complexes are one of the least explored and understood carbon complex species and, so far, have only been observed in the liquid phase,” The researchs lead author, Zhenhua Xu, told pv magazine. “In our work, we present the synthesis of bulk lead carbanion complexes and aims to explore their influence on 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%,” which was recently published in the Chemical Engineering Journal, the scientists explained that, with the carbanion treatment, the residual lead cation (Pb2+) at the interface could be neutralized and fully coordinated.
“A comprehensive investigation of perovskite films properties, using photoluminescence (PL) mapping and scanning electron microscope (SEM) images, revealed that carbanion passivation reduces defect-rich domains and decreases grain isolation on the perovskite surface,” Xu stated.
The group built the solar cell with a substrate made of indium tin oxide (ITO), a self–assembled monolayers (SAM) as an 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 illumination conditions, the device efficiency of up to 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 strong performance was primarily attributable to a high open-circuit voltage of 1.17 V and a minimal voltage loss of 0.38 V,” Xu further explained, adding that cell achieved the highest open-circuit voltage ever recorded for an inverted perovksite PV device. “The perovskite surface was anchored with strong Pb–C- bond, giving a stable device with lifespan over 3 months.”
Looking forward, the research group is planning to investigate other lead carbanion complexes with different cations, which are expected to synthesize more crystals, and should find applications beyond solar photovoltaics. |
