The optoelectronic properties of perovskite films are closely related to the film quality, so depositing dense, uniform, and stable perovskite films is crucial for fabricating high-performance perovskite solar cells (PSCs). CsPbI 2 Br perovskite, prized for its superb stability toward light soaking and thermal aging, has received a great deal of attention recently. However, the air instability and poor performance of CsPbI 2 Br PSCs are hindering its further progress. Here, an approach is reported for depositing high-quality CsPbI 2 Br films via the Lewis base adducts PbI 2 (DMSO) and PbBr 2 (DMSO) as precursors to slow the crystallization of the perovskite film. This process produces CsPbI 2 Br films with large-scale crystalline grains, flat surfaces, low defects, and long carrier lifetimes. More interestingly, PbI 2 (DMSO) and PbBr 2 (DMSO) adducts could significantly improve the stability of CsPbI 2 Br films in air. Using films prepared by this technique, a power conversion efficiency (PCE) of 14.78% is obtained in CsPbI 2 Br PSCs, which is the highest PCE value reported for CsPbI 2 Br-based PSCs to date. In addition, the PSCs based on DMSO adducts show an extended operational lifetime in air. These excellent performances indicate that preparing high-quality inorganic perovskite films by using DMSO adducts will be a potential method for improving the performance of other inorganic PSCs.

The Cs‐based inorganic perovskite solar cells (PSCs), such as CsPbI2Br, have made a striking breakthrough with power conversion efficiency (PCE) over 16% and potential to be used as top cells for tandem devices. Herein, I− is partially replaced with the acetate anion (Ac−) in the CsPbI2Br framework, producing multiple benefits. The Ac− doping can change the morphology, electronic properties, and band structure of the host CsPbI2Br film. The obtained CsPbI2−x Br(Ac)x perovskite films present lower trap densities, longer carrier lifetimes, and fast charge transportation compared to the host CsPbI2Br films. Interestingly, the CsPbI2−x Br(Ac)x PSCs exhibit a maximum PCE of 15.56% and an ultrahigh open circuit voltage (Voc) of 1.30 V without sacrificing photocurrent. Notably, such a remarkable Voc is among the highest values of the previously reported CsPbI2Br PSCs, while the PCE far exceeds all of them. In addition, the obtained CsPbI2−x Br(Ac)x PSCs exhibit high reproducibility and good stability. The stable CsPbI2−x Br(Ac)x PSCs with high Voc and PCE are desirable for tandem solar cell applications.

The HC(NH 2 ) 2 + (FA + ) is a well-known substitute to CH 3 NH 3 + (MA + ) for its capability to extend light utilization for improved power conversion efficiency for perovskite solar cells; unfortunately, the dark cubic phase (α-phase) can easily transition to the yellow orthorhombic phase (δ-phase) at room temperature, an issue that prevents its commercial application. In this report, an inorganic material (NbF 5 ) is developed to stabilize the desired α-phase perovskite material by incorporating NbF 5 additive into the perovskite films. It is found that the NbF 5 additive effectively suppresses the formation of the yellow δ-phase in the perovskite synthesis and aging process, thus enhancing the humidity and light-soaking stability of the perovskite film. As a result, the perovskite solar cells with the NbF 5 additive exhibit improved air stability by tenfold, retaining nearly 80% of their initial efficiency after aging in air for 50 d. In addition, under full-sun AM 1.5 G illumination of a xenon lamp without any UV-reduction, the perovskite solar cells with the NbF 5 additive also show fivefold improved illumination stability than the control devices without NbF 5 .

Research on the addition of suitable materials into perovskite film for improved quality is important to fabricate efficient and stable perovskite solar cells. An attempt to enhance the quality of perovskite is performed by incorporation of a bifunctional hydroxylamine hydrochloride (HaHc) into pristine perovskite solution. On the one hand, the chloride ion in HaHc changes the crystallization kinetic and defect state of the perovskite film and a high-quality perovskite film with larger grain size and lower defect density is obtained. Perovskite solar cell (PSC) with HaHc additive exhibit a power conversion efficiency (PCE) of 18.69% with less hysteresis, which is obviously higher than that of pristine cells (16.85%). On the other hand, the hydroxyl group in HaHc can form a strong hydrogen bond with iodide ion in perovskite film to impede the decomposition of the film when under thermal annealing or storing in air. As a result, the PSCs with HaHc additive show superior thermal and air stability to the pristine devices. These results indicate that the addition of HaHc in perovskite film can greatly improve the performance of PSCs as well as their thermal and air stability.

An ideal photodetector must exhibit a fast and wide tunable spectral response, be highly responsive, have low power consumption, and have a facile fabrication process. In this work, a self-powered photodetector with a graphene electrode and a perovskite photoactive layer is assembled for the first time. The graphene electrode is prepared using a solution transfer process, and the perovskite layer is prepared using a solution coating process, which makes the device low cost. Graphene can form a Schottky junction with TiO to efficiently separate/transport photogenerated excitons at the graphene/perovskite interface. Unlike the conventional photovoltaic structure, in this photodetector, both photogenerated electrons and holes are transported along the same direction to graphene, and electrons tunneled into TiO are collected by the cathode and holes transported by graphene are collected by the anode; therefore, the photodetector is self-powered. The photodetector has a broad range of detection, from 260 to 900 nm, an ultrahigh on-off ratio of 4 × 10, rapid response to light on-off (<5 ms), and a high level of detection of ∼10 Jones. The high performance is primarily due to the unique charge-transport property of graphene and strong light absorption properties of perovskite. This work suggests a new method for the production of self-powered photodetectors with high performance and low power consumption on a large scale.

A simple coalloying strategy is applied to improve the efficiency and stability of FA0.85MA0.15PbI3 perovskite solar cells (PSCs) by using cesium acetate (CsAc) as an additive. It is found that the simultaneous incorporation of cation (Cs+) and anion (Ac−) into the FA0.85MA0.15PbI3 film is an effective approach to realize lattice contraction, grain size enlargement, photoelectric properties improvement, band structure modulation, and therefore the optimization of the efficiency and stability of PSCs. At optimal CsAc alloying, the FA0.85MA0.15PbI3 PSCs achieve a maximum power conversion efficiency (PCE) of 21.95% and an average of over 21%. In addition, the alloyed PSCs retain 97% of their initial PCE values after aging for 55 days in air without encapsulation.

Inorganic cesium lead halide perovskite solar cells (PSCs), such as CsPbI2Br, have made a striking breakthrough with a power conversion efficiency of over 16%. However, CsPbI2Br is known to be very sensitive to moisture, and the intrinsic long‐term stability of CsPbI2Br film remains a critical challenge. Interface engineering has been proven to be an effective way for solving the instability‐to‐moisture issue and enhancing the performance of inorganic–organic hybrid PSCs, while there are a few reports on interface engineering for inorganic PSCs. Here, a conjugated polymer, poly(N‐alkyldiketopyrrolo‐pyrrole dithienylthieno[3,2‐b]thio‐phene) (DPP‐DTT), with high mobility is introduced as a novel interface passivation for CsPbI2Br PSCs, which can significantly reduce nonradiative recombination in perovskite, leading to significant enhancement in both efficiency and stability of CsPbI2Br PSCs. Through DPP‐DTT passivation, a champion efficiency of 15.14% is obtained in CsPbI2Br PSCs. Moreover, the Lewis base DPP‐DTT can serve as an ultrahydrophobic agent to hold the photovoltaic performance of CsPbI2Br PSCs under ambient environment with humidity or thermal stress. These results provide a simple while highly effective route of fabricating the highly efficient and stable inorganic PSCs.

In planar perovskite solar cells (PSCs), defect‐induced recombination at the interface between the perovskite and hole transport layer (HTL) leads to a large potential loss and performance deterioration. Therefore, an effective method for improving interfacial properties is critical to boost the performance and stability of PSCs. Herein, a novel surface engineering technology is reported for passivating the perovskite surface with the polyfluoro organic compound tris(pentafluorophenyl)boron (TPFPB), which can yield large perovskite grains, reduced defect densities, and improved charge transport and phase stability for the perovskite film, and enhanced power conversion efficiency (PCE) and stability for PSCs. Using this strategy, a champion FA0.85MA0.15PbI3 perovskite cell achieves a high PCE of 21.6% as well as significantly improved air and light stabilities. This work demonstrates that TPFPB is a promising material for crystallization control and defect passivation and paves a new path for mitigating defects and further increasing the performance of planar PSCs.