Suppressing Ion Migration by Synergistic Engineering of Anion and Cation toward High-Performance Inverted Perovskite Solar Cells and Modules.

Ion migration-induced intrinsic instability and large-area fabrication pose a tough challenge for the commercial deployment of perovskite photovoltaics. Herein, an interface heterojunction and metal electrode stabilization strategy is developed by suppressing ion migration via managing lead-based imperfections. After screening a series of cations and nonhalide anions, the ideal organic salt molecule dimethylammonium trifluoroacetate (DMATFA) consisting of dimethylammonium (DMA+) cation and trifluoroacetate (TFA-) anion is selected to manipulate the surface of perovskite films. DMA+ enables the conversion of active excess and/or unreacted PbI2 into stable new phase DMAPbI3, inhibiting photodecomposition of PbI2 and ion migration. Meanwhile, TFA- can suppress iodide ion migration through passivating undercoordinated Pb2+ and/or iodide vacancies. DMA+ and TFA- synergistically stabilize the heterojunction interface and silver electrode. The DMATFA-treated inverted perovskite solar cells and modules achieve a maximum efficiency of 25.03% (certified 24.65%, 0.1 cm2) and 20.58% (63.74 cm2), respectively, which is the record efficiency ever reported for the devices based on vacuum flash evaporation technology. The DMATFA modification results in outstanding operational stability, as evidenced by maintaining 91% of its original efficiency after 1520 h of maximum power point continuous tracking.

Trivalent Europium-Doped CsCl Quantum Dots for MA-Free Perovskite Solar Cells with Inherent Bandgap through Lattice Strain Compensation.

Cesium-formamidinium (Cs-FA) perovskites have garnered widespread interest owing to their excellent thermal- and photostability in achieving stable perovskite solar cells (PSCs). However, Cs-FA perovskite typically suffers from Cs+ and FA+ mismatches, affecting the Cs-FA morphology and lattice distortion, resulting in an enlarged bandgap (Eg ). In this work, "upgraded" CsCl, Eu3+ -doped CsCl quantum dots, are developed to solve the key issues in Cs-FA PSCs and also exploit the advantage of Cs-FA PSCs on stability. The introduction of Eu3+ promotes the formation of high-quality Cs-FA films by adjusting the Pb-I cluster. CsCl:Eu3+ also offsets the local strain and lattice contraction induced by Cs+ , which maintains the inherent Eg of FAPbI3 and decreases the trap density. Finally, a power conversion efficiency (PCE) of 24.13% is obtained with an excellent short-circuit current density of 26.10 mA cm-2 . The unencapsulated devices show excellent humidity stability and storage stability, and an initial PCE of 92.2% within 500 h under continuous light illumination, and bias voltage conditions is achieved. This study provides a universal strategy to address the inherent issues of Cs-FA devices and maintain the stability of MA-free PSCs to satisfy future commercial criteria.

Interfacial Engineering of Au@Nb2CTx-MXene Modulates the Growth Strain, Suppresses the Auger Recombination, and Enables an Open-Circuit Voltage of over 1.2 V in Perovskite Solar Cells.

Defects at the interface of charge transport layers can cause severe charge accumulation and poor charge transferability, which greatly affect the efficiency and stability of stannic oxide (SnO2)-based perovskite solar cells (PSCs). Herein, a new type of MXene (Nb2CTx-MXene) is applied to the interface of SnO2 layers to passivate the interfacial defects and promote charge transport. Nb2CTx-MXene in PSCs realizes the role of boosting the conductivity, reducing the tin vacancies in the interstitial void of the SnO2 layer, decreasing the defect density, and aligning the bandgap. Afterward, Nb2CTx-MXene is decorated with gold nanospheres, which has the ability to modulate the tensile strain of perovskites and suppress the Auger recombination. Eventually, the Au@Nb2CTx-MXene-modified device yields an excellent power conversion efficiency (PCE) of 23.78% with a relatively high open-circuit voltage of 1.215 V (Eg ∼ 1.60 eV). The unencapsulated devices maintain 90% of their initial PCE values after storage in the air with a relative humidity of 40% for 1000 h and remain above 80% of their initial efficiency after operation at the maximum power point for 500 h under 1 sun illumination. Our work provides an avenue to fabricate high-efficiency and stable PSCs with MXene adapting to commercial development.

Efficient single-component white light emitting diodes enabled by lanthanide ions doped lead halide perovskites via controlling Förster energy transfer and specific defect clearance.

Currently, a major challenge for metal-halide perovskite light emitting diodes (LEDs) is to achieve stable and efficient white light emission due to halide ion segregation. Herein, we report a promising method to fabricate white perovskite LEDs using lanthanide (Ln3+) ions doped CsPbCl3 perovskite nanocrystals (PeNCs). First, K+ ions are doped into the lattice to tune the perovskite bandgap by partially substituting Cs+ ions, which are well matched to the transition energy of some Ln3+ ions from the ground state to the excited state, thereby greatly improving the Förster energy transfer efficiency from excitons to Ln3+ ions. Then, creatine phosphate (CP), a phospholipid widely found in organisms, serves as a tightly binding surface-capping multi-functional ligand which regulates the film formation and enhances the optical and electrical properties of PeNC film. Consequently, the Eu3+ doped PeNCs based-white LEDs show a peak luminance of 1678 cd m-2 and a maximum external quantum efficiency (EQE) of 5.4%, demonstrating excellent performance among existing white PeNC LEDs from a single chip. Furthermore, the method of bandgap modulation and the defect passivation were generalized to other Ln3+ ions doped perovskite LEDs and successfully obtained improved electroluminescence (EL). This work demonstrates the comprehensive and universal strategies in the realization of highly efficient and stable white LEDs via single-component Ln3+ ions doped PeNCs, which provides an optimal solution for the development of low-cost and simple white perovskite LEDs.

Halide anions engineered ionic liquids passivation layer for highly stable inverted perovskite solar cells.

Long-term stability remains a great challenge for metal halide perovskite solar cells (PSCs). The utilization of ionic liquids (ILs) is a promising strategy to solve the stability problem. However, few studies have focused on controlling the halide anions of ILs, in which different organic cations can modulate the melting point of ILs and film crystal growth. Here, ILs with a 1-ethyl-3-methylimidazolium (EMIM+) cation and different halide anions (X = Cl, Br, and I) are employed in inverted PSCs. The results show that EMIMX can form a 1D passivation layer by the in situ growth technique and influence the surface morphology of the perovskite film. These EMIMX-treated layers simultaneously suppress the surface defects and nonradiative energy losses and improve the hydrophobic properties. As a result, a power conversion efficiency (PCE) of 20.0% is obtained for the EMIMBr-modified PSCs compared to 18.06% for the control device. Moreover, the unencapsulated devices maintain more than 90% of their initial PCE over 3000 h under ambient air, which is among the best long-term stabilities reported for NiOx-based inverted PSCs. It also retains 74.2% and 49.5% of the initial PCE value after aging under harsher conditions, such as an 85 ± 5% relative humidity (RH) environment and at 85 °C for 48 h, respectively.

Highly efficient ligand-modified manganese ion doped CsPbCl3 perovskite quantum dots for photon energy conversion in silicon solar cells.

Manganese ion doped CsPbX3 perovskite quantum dots (QDs) demonstrate high absorption of ultraviolet (UV) light and efficient orange emission with a large Stokes shift, and are almost transparent to visible light, which are ideal photon energy converters for solar cells. In this work, Mn2+ ion doped CsPbCl3 QDs were synthesized by incorporating a long-chain ammonium ligand dodecyl dimethylammonium chloride (DDAC), in which the DDAC ligand not only played the role of replacing the surface ligands of QDs, but also enhanced the efficiency and stability of Mn2+ ion doped QDs. The as-prepared QD sample displayed a photoluminescence quantum yield (PLQY) as high as 91% and served as a photon energy converter for silicon solar cells (SSCs). The photoelectric conversion efficiency (PCE) of SSCs increased from 19.64% to 20.65% with a relative enhancement of 5.14%. This work displays a method to tune the efficiency of QDs by modifying the surface ligands and an efficient photon energy converter for SSCs, which is of great importance for practical applications.

Unraveling the Dual-Functional Mechanism of Light Absorption and Hole Transport of Cu2CdxZn1-xSnS4 for Achieving Efficient and Stable Perovskite Solar Cells.

Broadening the near-infrared (NIR) spectrum of device is critical to further improve the power conversion efficiency (PCE) of the perovskite solar cells (PSCs). In this work, novel Cu2CdZn1-xSnS4 (CZTS:Cd) film prepared by thermal evaporation method was employed as the NIR light-harvesting layer to complement the absorption of the perovskite. At the same time, Au nanorods (NRs) were introduced into the hole-transporting layer (HTL) to boost the utilization of CZTS:Cd to NIR light through localized surface plasmon effect. The perovskite/CZTS:Cd and Au NR-integrated PSCs can extend the photoelectric response to 900 nm. And more, the well-matched energy levels between CZTS:Cd and perovskite can effectively extract holes from perovskite and depress the charge carrier recombination. As a result, the champion PSC device insulating with CZTS:Cd and Au NRs demonstrates a remarkably increased PCE from 19.30 to 21.11%. The modified PSC devices also demonstrate highly improved long-time stability. The device retains a PCE of 87% after 500 h even under air with a relative humidity of 85%, implying the superior humidity stability of the devices with CZTS:Cd. This work suggests that perovskite/inorganic-integrated structure is a promising strategy to broaden and boost the NIR response of the PSCs.