Jihuai Wu

The energy density of lithium-ion capacitors can be improved by using a polypyrrole/graphene oxide (PPy/GO) composite cathode by generating pseudocapacitance through the doping/undoping of PF ₆ ⁻ ions from the electrolyte.

Inverted lead halide amine perovskite solar cells (PSCs) are promising for efficient and scalable photovoltaics, yet the charge-carrier and energy loss at the buried interface between the hole-transport layer and perovskite layer remain a major source of limited performance and stability because of nonideal energy alignment and defect-assisted carrier nonradiative recombination. Here, a cyano-functionalized carbazole small molecule, 9H-carbazole-3-carbonitrile (3-CNCZ), as a multifunctional modulator, is introduced into the buried interface in self-assembled monolayer (SAM)-based inverted PSCs. Owing to its polar cyano group and π-conjugated carbazole framework, 3-CNCZ enhances intermolecular interaction and reduces the trap-state density, promotes overlayer perovskite crystallization, and modulates interfacial charge redistribution and energy level alignment. The synergistic modulation of cyano-functionalized carbazole leads to a 55.5% longer carrier lifetime and a decrease of the surface contact potential difference from −151 mV to −611 mV. As a result, the 3-CNCZ-modulated inverted PSCs achieve a champion power conversion efficiency of 26.31%. Meanwhile, the unencapsulated devices retain 96% of their initial efficiency after 600 h of maximum power point tracking (MPPT). This work provides a single-molecule strategy for synergistically modulating the buried interface and reducing the charge-carrier loss and energy loss in SAM-based inverted PSCs.

Perovskite solar cells (PSCs) have become a research hotspot in the photovoltaic field, while the fluorine-doped tin oxide substrate/electron transport layer (FTO/ETL) interface is a blind spot in PSC research. Hence, a nanolayer of alkali metal fluoride (MF: LiF, NaF, KF) is inserted into the interlayer between FTO and SnO2 ETL. In the subsequent annealing, F– anions are firmly adsorbed on the surface of the FTO anode, while some M+ cations diffuse into the SnO2 and perovskite to form a like-diffuse electric double layer (L-DEDL) and a built-in dipole field at the FTO/ETL interface. The L-DEDL optimizes the energy level alignment and suppresses the reverse migration of ions. Compared to K and Na, Li has a smaller ionic radius and a smaller electronegativity difference with F element, thus Li is more prone to diffuse and produce more significant modulation effects. Therefore, the LiF-modified device achieved a power conversion efficiency (PCE) of 26.13% along with improved stability, while the pristine device had a PCE of only 23.07%.

Power conversion efficiency (PCE) is limited by the high density of defects and poor energy level alignment of the SnO ₂ /perovskite (PVK) buried interface in perovskite solar cells (PSCs). Herein, a synergistic molecular interface engineering strategy is designed by using an ionic liquid, 1‐dodecyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl) imide salt (DMIMTFSI) to modify this critical interface. The strong electron‐withdrawing TFSI ⁻ anion induces a downward shift of the conduction band of SnO ₂ , thereby optimizing energy level alignment and facilitating electron extraction. Meanwhile, the DMIM ⁺ cation passivates interfacial defects through robust chemical interactions with Pb ²⁺ and I ⁻ ions. Furthermore, the long alkyl chain of DMIMTFSI templates the formation of an ordered porous PbI ₂ morphology, which improves the crystallinity of the overlying PVK film. The DMIMTFSI modification reduces the trap‐state density by 31.86%, prolongs the carrier lifetime by 39.42%, and increases the built‐in potential from 0.95 to 1.02 V. Therefore, the DMIMTFSI‐modified device achieves a PCE of 24.14%, significantly outperforming the pristine device of 22.34%. The unencapsulated modified device retained 87% of its initial PCE after being stored for 1000 h under ambient conditions, demonstrating excellent environmental stability. This work provides a viable multifunctional interface engineering pathway toward high‐performance and stable PSCs.

The unclear mechanisms and dominant types of defects causing degradation hinder the stability of perovskite solar cells, leading to increased operating costs and limiting their commercialization. In this study, we identify deep‐level I _FA and I _Pb defects as the primary cause of device degradation based on quantitative analysis of capacitance‐frequency spectra combined with detailed balance theory, although the concentrations are lower than those of commonly believed shallow‐level defects by three orders of magnitude. To mitigate these issues, we design a non‐intercalary ligand coordination strategy through dual‐end electropositive 3TU ²⁺ ions, which effectively passivated the degradation‐induced deep‐level defects. This approach results in a significant improvement in quasi‐Fermi level splitting alignment, reducing energy loss at the rear interface by an order of magnitude (from 1.46% to 0.62%). In addition to achieving a certified efficiency of 25.56%, our devices demonstrate an extrapolated T ₈₀ lifetime exceeding 10 years, as per the ISOS‐LC‐1 protocol. This improvement reduces the levelized cost of energy to 0.148$ kWh ⁻¹ , on par with silicon photovoltaics, thus enhancing the commercial viability of perovskite solar cells.