吴晓晓

An organic photovoltaic (OPV) formulation is developed, which suggests a low synthetic complexity and a competitive figure of merit. The prepared module exhibits a maximum power conversion efficiency (PCE) of 10% when using solution‐processed material as the hole‐transporting layer and simultaneously exhibits outstanding stability, which will benefit the commercialization of highly efficient OPV products.

A scalable and accessible photoactive formulation with a low synthetic complexity (SC) index is utilized in organic photovoltaic (OPV) fabrication. The formulation readily dissolves in nonchlorinated solvents, and the corresponding photoactive films can be processed by various coating methods to fabricate devices with power conversion efficiencies (PCEs) of 16.1% and 15.2% when using vacuum‐based molybdenum oxide and solution‐processable conducting polymer as the hole transporting layer in the inverted structure, respectively. This prepared device shows superior stability under light exposure. The PCE is maintained 94% of the initial values after 1080 h of light soaking at 100 mW cm⁻². Furthermore, the figure of merit based on the ratio of the SC index and PCE indicates the benefit of this formulation for OPV manufacturing, showing the feasibility of commercialization. Eventually, a PCE of 10.3% is demonstrated for a mini‐module fabricated under ambient conditions, with an active area of 32.6 cm². To our knowledge, this PCE is one of the largest values reported to date for a green solvent and an all‐solution‐processed OPV module with an inverted architecture.

Herein, a metal oxide bilayer combining ZnO and TiO₂ compact films (ZnO/TiO₂) is implemented as an electron transport material (ETM) for solution‐processed Sb₂S₃ planar solar cells. The ZnO/TiO₂ bilayer promotes charge injection, decreases series resistance and shutting paths, and leads to the reduction of charge recombination.

Electron transport materials (ETMs) are considered a keystone component of third‐generation solar cells. Among the alternative ETM, metal oxide bilayers have attracted increasing attention due to their easy processing and tunability of cascade energy alignment. Herein, a metal oxide bilayer that combines ZnO and TiO₂ compact films (ZnO/TiO₂) is implemented as ETM for solution‐processed Sb₂S₃ planar solar cells. The bilayer ETM achieves the highest photovoltaic performance when compared with devices based on single ETM. Thus, the optimized device based on ZnO/TiO₂ ETM yields a champion efficiency of 5.08% with an open‐circuit voltage of 0.58 V and a current density of 16.17 mA cm⁻². Using surface photovoltage, electrochemical impedance spectroscopy, and current density–voltage analyses, it is demonstrated that the use of ZnO/TiO₂ promotes charge injection, decreases series resistance and shutting paths, and leads to the reduction of charge recombination at the ETM/Sb₂S₃ interface.

A universal crystal engineering method based on anion exchange is proposed and developed to grow crystalline perovskite thin films. Highly crystalline perovskite films with preferred crystal orientation and micrometer‐scale grains are presented via annealing perovskite films in saturated MAI vapor. Perovskite solar cells based on crystal engineering show improved efficiency from 21.07% to 22.26%.

Crystalline, dense, and uniform perovskite thin films are crucial for achieving high‐power conversion efficiency solar cells. Herein, a universal method of fabricating highly crystalline and large‐grain perovskite films via crystal engineering is demonstrated. Anion exchange of Cl⁻ and I⁻, and annealing perovskite films, in an ultraconfined and uniform temperature enclosed space with saturated MAI (or FAI) vapor using hot‐pressing sublimation technology are conducted. This process ensures a rapid crystal growth rate due to fast exchange between the gas phase and the crystalline film to reduce vertically oriented grain boundaries. The generation of the commonly observed PbI₂ phase is also suppressed due to the chemical equilibrium state during the thermal annealing process. Using this approach, pinhole‐free perovskite films with preferred crystal orientation and micrometer‐scale grains are obtained, leading to a high steady‐state efficiency of 22.15% based on mixed‐cation perovskite composition. In addition, devices based on different perovskite compositions all exhibit enhanced photovoltaic performance based on the crystal engineering method. The device (without encapsulation) has an efficiency loss of about only 4% after 2520 h of aging in ambient conditions and retains 87% of its initial efficiency after 1000 h of continuous 1 Sun light soaking, thus demonstrating considerably improved stability.

Lead halide perovskites are unstable in high-polarity solvents. Multifunctional melamine foam (MF) is selected to assist perovskites, not only realizing efficient and long-term photocatalytic carbon dioxide reduction in pure water reaction medium, but also preventing the pollution of toxic lead leakage toward the environment, owing to the strong adherence between MF and perovskites.

Application of lead halide perovskites in CO₂ photoreduction in pure H₂O medium is restricted, owing to the inherent instability and high toxicity of lead. Herein, 3D melamine foam (MF) with an interconnected porous structure is selected as a multifunctional assistance to solve these problems. Three-dimensionality of MF can avoid direct touches of CsPbX₃ (X = Br, I) with liquid H₂O, preventing damage of H₂O. Porosity of MF can accelerate H₂O evaporation by its strong adsorption and photothermal effects, which will overcome the drawback of low CO₂ solubility in aqueous solution, achieving a quick and sufficient mixture of CO₂ with H₂O vapor. These functions contribute to realize highly efficient CO₂ reduction by CsPbX₃ in pure H₂O medium. The best products and electron consumption yields of the composite reach 42.08 and 161.84 μmol g⁻¹ h⁻¹, respectively,  which surpass most of the other CsPbX₃-related works in H₂O or organic reaction media. MF/CsPbBr₃ also presents long-term stability, with product yields not showing any obvious decrease after continuous reaction for 104 h. Moreover, strong adherence of MF toward perovskites allows a good recoverability of CsPbX₃, avoiding pollution of lead leakage to the environment.

A record efficiency of 15.24% is achieved for organic solar cells with an area of ≥1 cm² with D18:Y6 as absorber material. The optimized cell design minimizes resistive losses due to the indium tin oxide (ITO) electrode. The cell is very homogeneous and is hardly affected by shunts, as revealed by light beam‐induced current, electroluminescence, and dark lock‐in thermography imaging.

In organic photovoltaics, high power conversion efficiencies (PCE) are mostly achieved on device areas well below 0.1 cm². Herein, organic solar cells based on a D18:Y6 absorber layer on an active area of ≥ 1 cm² with a certified PCE of 15.24% are reported. The impacts of the sheet resistance of the transparent electrode and the cell design are quantified by means of full optical device simulations and an analytical electrical model. Three imaging methods (light beam‐induced current, dark lock‐in thermography, and electroluminescence [EL]) are applied and reveal a strong homogeneity of the record cell. Nevertheless, it is found that there is substantial room for improvement mostly in current but also in fill factor and that a PCE of 18.6% on ≥1 cm² is feasible with this absorber material. Further, photoluminescence (PL) and EL spectroscopy reveal that both emissions occur at the same wavelength(s) and are very similar to the PL spectrum of a pure Y6 acceptor film. The latter points strongly toward electronic coupling between the S1 states of the acceptor and the charge transfer states at the donor/acceptor interface.

Two SiO _x passivation architectures are applied in ultrathin Cu(In,Ga)Se₂ (CIGS) solar cells. Both passivation approaches result in devices with higher performance compared with a reference nonpassivated device. The potential to use SiO _x as passivation material, deposited by a high throughput industrial technique based on microelectronics processing, yields promising results toward high‐performance low‐cost ultrathin CIGS solar cells for energy conversion.

Herein, it is demonstrated, by using industrial techniques, that a passivation layer with nanocontacts based on silicon oxide (SiO _x ) leads to significant improvements in the optoelectronical performance of ultrathin Cu(In,Ga)Se₂ (CIGS) solar cells. Two approaches are applied for contact patterning of the passivation layer: point contacts and line contacts. For two CIGS growth conditions, 550 and 500 °C, the SiO _x passivation layer demonstrates positive passivation properties, which are supported by electrical simulations. Such positive effects lead to an increase in the light to power conversion efficiency value of 2.6% (absolute value) for passivated devices compared with a nonpassivated reference device. Strikingly, both passivation architectures present similar efficiency values. However, there is a trade‐off between passivation effect and charge extraction, as demonstrated by the trade‐off between open‐circuit voltage (V _oc) and short‐circuit current density (J _sc) compared with fill factor (FF). For the first time, a fully industrial upscalable process combining SiO _x as rear passivation layer deposited by chemical vapor deposition, with photolithography for line contacts, yields promising results toward high‐performance and low‐cost ultrathin CIGS solar cells with champion devices reaching efficiency values of 12%, demonstrating the potential of SiO _x as a passivation material for energy conversion devices.

High efficiency and humidity‐resistant flexible perovskite solar cells (FPSCs) are fabricated, using a SnO₂/Al(acac)₃ bilayer as the electron transfer layer. FPSCs present long‐time stability in ambient conditions (>50% relative humidity) without encapsulation, while yielding a power conversion efficiency (PCE) of up to 20.87%. That may open a new way to improve the stability of FPSCs.

Flexible perovskite solar cells (FPSCs) with high efficiency and excellent mechanical flexible properties have attracted enormous interest as a promising photovoltaic technology in recent years. However, the performance or stability of FPSCs is still far inferior to that of conventional glass‐based perovskite solar cells (PSCs). Herein, a cross‐linking agent called aluminum acetylacetonate (Al(acac)₃) is introduced as an interface layer between electron transport layer and perovskite absorber. Due to the well‐matched energy levels and improved grain size and crystallinity of the perovskite, a champion device with the highest power conversion efficiency (PCE) of 20.87% is achieved on the FPSCs. The device retains about 80% of its initial performance after 1000 h under >50% relative humidity without encapsulation. In addition, attributed to the Al(acac)₃ super bending resistance, more than 91% of the original PCE is retained after 1500 bending cycles. This work proposes the substrate side optimization for improving device efficiency and stability which may provide a novel concept for promoting the development of FPSCs.

Bearing high hole mobility and appropriate energy levels, an organic small molecule 2,7‐bis(4‐octylphenyl)naphtho[2,1‐b:6,5‐b 0] difuran (C₈‐DPNDF) is introduced as a dopant‐free hole transporting material in inverted perovskite solar cells. The device with C₈‐DPNDF as HTM shows a decent power conversion efficiency of 17.5% and can keep 92% of its initial value after 30 days in ambient air.

Hole transport material (HTM) is a significant constituent in perovskite solar cells (PSCs). However, HTM generally is not utilized in its pristine form but with dopants (such as lithium salt, tert‐butyl pyridine, F₄‐TCNQ), which accelerates device degradation and leads to poor stability. Therefore, dopant‐free HTM is highly desirable to fabricate stable devices. Herein, a fused furan organic small molecule (C₈‐DPNDF) is introduced as a dopant‐free HTM in inverted PSCs. As a potential HTM candidate, C₈‐DPNDF shows excellent properties, such as high hole mobility, matched energy level with perovskite, and resistance to perovskite precursor solution. As a result, the device based on C₈‐DPNDF as HTM shows a power conversion efficiency (PCE) of 17.5%, compared with 17.1% of the control device based on classic poly(bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine) (PTAA) as the HTM. In addition, the unencapsulated device based on C₈‐DPNDF as HTM keeps 92% of its initial PCE after 30 days of storage in ambient air with a relative humidity of ≈40%. This finding is expected to pave the way toward stable and highly efficient inverted PSCs based on dopant‐free HTMs.