Perovskite interface engineering is crucial to improving the performance and stability of perovskite solar cells (PSCs ), and 2D/3D perovskite heterojunctions have shown particular promise in this regard. However, defects at the top and bottom interfaces of 3D perovskite light absorbers can reduce the performance and operational stability of perovskite solar cells (PSCs) due to charge recombination, ion migration, and electric field inhomogeneity.
In view of this, Randi Azmi, Stefaan De Wolf and others at King Abdullah University of Science and Technology demonstrated that long alkylamine ligands can generate near-phase pure 2D perovskites at the top and bottom 3D perovskite interfaces and effectively solve solved the above problems. On the back-contact side, the alkylamine ligands used were found to modulate 2D calcium by enhancing interactions with the substrate through acid-base reactions with phosphonic acid groups in the organic hole-transporting self-assembled monolayer molecules used Formation of titanium ore. Under this condition, the inverted PSCs with double-sided 2D/3D heterojunction achieved a photoelectric conversion efficiency (PCE) of 25.6% (certified 25.0%) after 1000 hours of 1-sun illumination in air at 85 degrees Celsius . 95% of the original PCE is still retained .
Bottom interface 2D/3D heterojunction
The authors developed an inverted (pin) PSC with hole-collecting contacts ( p-type ). In order to solve the problem of forming a 2D/3D heterojunction at the bottom of the perovskite film, the HBzA ligand was mixed into the 2PACz SAM solution, using HBzA and 2PAC reacts to form ionic bonds and the -OH group in HBzA can form hydrogen bonds with -PO(OH) 2 and ITO to further strengthen adhesion. This combination is beneficial to their adhesion to the substrate during perovskite processing. , and helps form a 2D perovskite layer underneath the 3D perovskite layer. After successfully attaching HBzA ligands to the ITO/2PACz surface, a 3D perovskite ink was deposited by spin coating and multiple characterizations showed that 2D perovskite formation at the bottom interface regulates perovskite crystallization.
Figure 1 2D/3D heterojunction at hole-selective bottom interface
3D/2D heterojunction at top interface
For the 3D/2D heterojunction at the top interface, the authors developed a simple two-step mixing method to form a pure phase 2D perovskite layer, and the results confirmed the success of the method to control the phase purity and dimensionality of 2D perovskite. The higher dimensions of the 2D perovskite (n > 1) passivation layer are crucial because of the higher conductivity of the smaller organic cation interface. The authors determined the crystal orientation and dimensions of the 2D perovskite layer through GIWAXS measurements and visualized the 2D perovskite formation and orientation at the top contact through HR-STEM, demonstrating the robustness of the hybrid approach to the formation of perovskite heterostructures.
Figure 2 3D/2D heterojunction with electron-selective top interface
Device Performance and Characteristics
The authors optimized the ratio between the 2PACz SAM and 2D ligands at the bottom 2D/3D passivation of the alkylamine-based 2D ligands, the thickness of the alkylamine ligands, and the heterojunction PbI2 thickness , respectively . Double-sided 2D/3D heterojunction passivation was used for the inverted PSC, and a maximum PCE of 25.63% was demonstrated under reverse conditions. The generalizability of the method was demonstrated by testing other perovskite compositions with various hole-transporting SAM molecules. The V OC ×FF value of the bifacial 2D/3D heterojunction device is approximately 91% of the Shockley-Queisser limit, which is one of the highest values among PSCs with top-only or overall passivation.
The authors also used space charge current limiting (SCLC) and thermal admittance spectroscopy (TAS) analysis to determine the control and trap states of double-sided 2D/3D passivation of perovskite films, dual 2D/3 perovskite passivation devices N t has lower Nt values in all energy defect levels, indicating that 2D perovskite passivation fully passivates both shallow and deep defects in the perovskite film. The authors evaluated the long-term stability of the encapsulated PSCs under light stress and thermal stress, and the relative PCE loss of the device after 1-sun in air and 85°C open circuit conditions was only 5% after more than 1000 hours.
Figure 3 Equipment performance and stability analysis
Azmi, R., Utomo, DS, Vishal, B. et al. Double-side 2-dimensional/3-dimensional heterojunctions for inverted perovskite solar cells. Nature (2024).
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