Scientists fabricate efficient and stable perovskite solar cells using low-dimensional perovskitoids

Scientists from the Xi'an Jiaotong University, Chinese Academy of Science and City University of Hong Kong have reported the fabrication of a highly stable perovskite solar cell by capping the photoactive layer with low-dimensional (LD) perovskitoids.

Atomic structure of (A) (p-PBA)Pb2I6 (1D) and (B) (m-PBA)2PbI6 (0D). Image from study

'Perovskitoids have the potential to effectively modify 3D perovskite due to its diverse PbI₆ connection styles and high stability,' the researchers stated, referring to the properties of the 1D and 0D capping layer materials used for 3D perovskite (m-PBA)₂PbI₆. 'Both 1D and 0D perovskitoids have intrinsically low defect densities and can withstand relatively high lattice strains; thus, they can serve as blocking channels for undesired Shockley-Read-Hall recombination and material degradation.'

The film composition was analyzed through grazing-incidence wide-angle x-ray scattering (GIWAXS) measurements and the LD perovskitoids were found able to restrain the formation of the photoinactive nonperovskite phase.

The growth of the perovskitoids on the 3D perovskite, according to the team, enables effective and all-around passivation of the perovskite surfaces and grain boundaries. The thickness of the perovskite film is around 650 nm, which they claim can ensure sufficient absorption of light. The LD perovskitoid structure was coated at the surface of the 3D perovskite with an overall thickness of approximately 5 nm.

The solar cell was built with an indium tin oxide substrate, an electron transport layer (ETL) based on Tin(IV) oxide (SnO₂), the perovskite layer, a spiro-OMeTAD hole-blocking layer, and a gold (Au) metal contact. The best performing device achieved a power conversion efficiency of 24.18%, an open-circuit voltage of 1.151 V, a short-circuit current of 25.96 mA/cm², and fill factor of 80.91%.

The cell was also found to maintain 90% of its initial efficiency after being stored in ambient air for 2,000 hours and after 800 hours of continuous illumination under maximum power point operating conditions.

'The significant improvement of stability in 3D/LD PSC is attributed to better moisture resistance of LD capping layers, reduced trap density of 3D perovskite surface, and tight bonding of the 3D/LD interface,' the research group stated. 'This study establishes a new material engineering scheme for perovskite solar cells with enormous numbers of 1D and 0D perovskitoid candidates that can be used to further improve the PSC performance and stability.'