Inverted-structure perovskite solar cells (PVSCs) applying NiO x as the hole transport layer (HTL) have attracted increasing attention. It is still a challenge to optimize the contact between NiO x and the perovskite layer and to suppress energy loss at the interface. In this study, interface engineering was carried out by modifying the NiO x layer with different polymers such as polystyrene, poly(methyl methacrylate) (PMMA), or poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) to improve the surface contact between NiO x and the perovskite, to decrease the defect states, and to make the energy level alignment better. The NiO x /PMMA-based device presents a V oc as high as 1.19 V because of the improved interfacial contact and the interaction of the carbonyl and methoxy group with Pb 2+ . The NiO x /PTAA-based device with the structure ITO/NiO x / PTAA/(MAPbI 3 ) 0.95 (MAPbBr 2 Cl) 0.05 /PCBM/BCP/Ag exhibits the highest power conversion efficiency of 21.56% with a high V oc of 1.19 V. The enhanced performance can be attributed to the deepened highest occupied molecular orbital level of NiO x /PTAA, which matched well with that of the perovskite and suppressed interface energy loss as well. This work provides a facile approach for efficiently improving the V oc of NiO x -based PVSCs.

Although the 2D spacer modification is widely studied in perovskite solar cells (PVSCs), the energy level alignment between the 2D/3D interfaces makes it unfavorable for top surface passivation in the inverted p-i-n device structure. To address this issue, the effect of bottom interface modification is studied with three representative 2D spacers, i.e., the Ruddlesden-Popper 2D spacer, Dion-Jacobson 2D spacer, and strong passivation 2D spacer, in inverted p-i-n PVSCs. After optimization, the PVSCs with these 2D spacer modifications universally exhibit the best efficiencies of ≈21.6%, which constitutes dramatic improvement compared to the control device (20.7%). By lifting off the perovskite layer, the optoelectronic properties of the bottom surface are studied, and the mechanism underlying the improved device performance is unveiled to be uniformly originated from the formation of 2D/3D heterojunction, where the cascade valence band facilitates the hole collection and electron back scattering field suppresses the charge recombination at the anode interface. Besides, the unencapsulated device retains 90% of initial efficiency after 30 days of storage in ambient air with a relative humidity of 30 ± 5%, indicating excellent stability against moisture and oxygen. This study provides insight into the bottom interface modification with diverse 2D spacers for high-performance p-i-n structured PVSC devices.

Developing indium‐tin‐oxide (ITO)‐free flexible organic photovoltaics (OPVs) with upscaling capacity is of great significance for practical applications of OPVs. Unfortunately, the efficiencies of the corresponding devices lag far behind those of ITO‐based rigid small‐area counterparts. To address this issue, an advanced device configuration is designed and fabricated featuring a top‐illuminated structure with ultrathin Ag as the transparent electrode. First, a conjugated polyelectrolyte layer, i.e., PCP‐Li, is inserted to effectively connect the bottom Ag anode and the hole transport layer, achieving good photon to electron conversion. Second, charge collecting grids are deposited to suppress the increased resistance loss with the upscaling of the device area, realizing almost full retention of device efficiency from 0.06 to 1 cm2. Third, the designed device delivers the best efficiency of 15.56% with the area of 1 cm2 on polyimide substrate, representing as the record among the ITO‐free, large‐area, flexible OPVs. Interestingly, the device exhibits no degradation after 100 000 bending cycles with a radius of 4 mm, which is the best result for flexible OPVs. This work provides insight into device structure design and optimization for OPVs with high efficiency, low cost, superior flexibility, and upscaling capacity, indicating the potential for the future commercialization of OPVs.

High‐performance perovskite solar cells (PVSCs) with low energy consumption and green processing are highly desired, but constrained by the difficulty in morphology control and the poor understanding on morphology evolution mechanisms. To address this issue, here we studied the effect of antisolvents on the perovskite film formation. We found that both the antisolvents and the perovskite composition affect the perovskite film morphology greatly via influencing the intermediate phase, and different perovskite compositions require different antisolvents to reach the optimal morphology. This provides the opportunity to achieve high‐performance PVSCs with green antisolvent, that is, isopropanol (iPA) by changing the perovskite compositions, and leads to a power conversion efficiency (PCE) of 21.50% for PVSCs based on MA0.6FA0.4PbI3. Further, we fabricated “fully green” PVSCs with all layers prepared by green solvents, and the optimal PCE can reach 19%, which represents the highest among PVSCs with full‐green processing. This work provides insight into the perovskite morphology evolution and paves the way toward “green” processing PVSCs.

2D PVSCs with “favorable” ion accumulation are realized via thermal–light post-treatment, which increases the built-in potential and device performance.

To address the instability issue, all inorganic perovskites composed of CsPbX 3 (X represents for I, Br, and Cl) have been developed. [6,7] Recently, the efficiency of CsPbI 3 PSCs has reached 21%. [8,9] Unfortunately, the photoactive α phase of CsPbI 3 tends to degrade to yellow δ phase at room temperature due to their unfavorable Goldschmidt tolerance factor (GTF) of 0.81. [10][11][12] Incorporating the smaller-size Br − can tune the tolerance factor to the ideal value of 1 for perovskite structure, but this results in the photoinduced halide segregation, which makes the perovskite film and device unstable under illumination. [13][14][15] Although the CsPbBr 3 is phase-stable under both heat and illumination, its bandgap (≈2.3 eV) is unsuitable for solar cell application due to its poor coverage with solar spectra. [11,12] By balancing the above pros and cons, the CsP-bI 2 Br seems one of the best choices among the all inorganic perovskites, which shows preferable bandgap (≈1.9 eV) and enhanced phase stability. Moreover, wide-bandgap perovskites are suitable for fabricating perovskite/Si or perovskite/organic tandem solar cells. In fact, the 1.9 eV bandgap of CsPbI 2 Br is also very suitable for perovskite/organic tandem solar cells to match with the state-of-art Y6 derivatives organic photovoltaics systems, [16][17][18][19][20] and this has been demonstrated by most recent works, which validate the great potential of the CsPbI 2 Br/organic tandem solar cells. [21,22] Besides the phase stability, the crystallinity and morphology of perovskite films also play an important role in determining the photovoltaic performance of PSCs. Controlling the nucleation and crystallization process, as is affected by the precursor solution formulation and the film formation process, is vital to obtain a high-quality perovskite film. [23][24][25][26][27][28] Wang et al. developed a solvent-controlled growth method to control the nucleation process of CsPbI 2 Br films, and obtained high quality CsPbI 2 Br films and PSC delivered a power conversion efficiency (PCE) of 14%. [29] Chen et al. developed an antisolvent assisted gradient thermal annealing method to control film formation process of CsPbI 2 Br films and finally reached a PCE of 16.07%. [30] Besides, the dynamic hot-air-assisted method has been proposed to control the crystallization of perovskite film for highly crystalline, pinhole-free black-phase CsPbI 2 Br films. [31,32] Recently, a relatively simple method was given by Byranvand et al., where they found high quality CsPbI 2 Br films with micrometer-scale grain size can be reached via simply extending the time of The inorganic perovskite solar cells (IPSC) are promising in the context of simultaneously delivering high efficiency and good stability. Developing a high-performance and larger band gap IPSC is particularly in demand for commercialization due to their suitability to match with the prevailing silicon solar cells for tandem devices, while this is hindered by the poor morphology and phase stability of inorgan...

Maximizing the efficiency while exploiting fully inherent advantages of organic photovoltaics (OPVs), e.g., ultra-flexibility, ultra-lightweight, rich color, etc., is of great significance for the commercialization of OPVs. To address it,...

Comprehensive Summary The surface properties and chemical interactions are critical for perovskite solar cells (PVSCs). In this work, we show that the polypropylene glycol (PPG) can simultaneously passivate the NiOx surface and grain boundaries of perovskite films, allowing more efficient charge transfer at the anode interface and reducing the recombination of PVSCs. As a result, the open‐circuit voltage (Voc) of MAPbI3 based inverted PVSCs increases from 1.087 V to 1.127 V, and the short‐circuit current density (Jsc) is increased from 20.87 mA·cm–2 to 22.32 mA·cm–2, thereby realizing the improvement of the device power conversion efficiency (PCE) from 18.34% to 20.12%. Moreover, the steady‐state output of the PVSCs is remarkably improved by incorporating PPG. Further analysis of surface properties suggests that part of the PPG at the interface can permeate into the precursor solution with the help of DMF solvent and remain in the perovskite layer to form a concentration gradient. The ether bond of PPG and the uncoordinated Pb2+ in the perovskite are coordinated to achieve passivation effects and improve device performance. Our work provides a rational strategy for the preparation of high‐performance PVSCs.