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Inverted planar perovskite solar cells offer opportunities for a simplified device structure compared with conventional mesoporous titanium oxide interlayers. However, their lower open-circuit voltages result in lower power conversion efficiencies. Using mixed-cation lead mixed-halide perovskite and a solution-processed secondary growth method, Luo et al. created a surface region in the perovskite film that inhibited nonradiative charge-carrier recombination. This kind of solar cell had comparable performance to that of conventional cells. Science , this issue p. 1442 High open-circuit voltages were achieved for planar perovskite solar cells by creating a graded junction. The highest power conversion efficiencies (PCEs) reported for perovskite solar cells (PSCs) with inverted planar structures are still inferior to those of PSCs with regular structures, mainly because of lower open-circuit voltages ( V oc ). Here we report a strategy to reduce nonradiative recombination for the inverted devices, based on a simple solution-processed secondary growth technique. This approach produces a wider bandgap top layer and a more n-type perovskite film, which mitigates nonradiative recombination, leading to an increase in V oc by up to 100 millivolts. We achieved a high V oc of 1.21 volts without sacrificing photocurrent, corresponding to a voltage deficit of 0.41 volts at a bandgap of 1.62 electron volts. This improvement led to a stabilized power output approaching 21% at the maximum power point.

Highlights By anchoring the perovskite sites with the functional groups of CzBP (P = O···Pb, N–H···I and P = O···N–H), the bulk nonradiative recombination is suppressed and ion migration is inhibited. Doping perovskite films with CzBP led to enhanced intercrystallite interactions in the bulk and improved photoluminescence quantum yield. Using a typical electron-rich moiety as the π-linker to replace the classic alkyl spacer in CzBP facilitated the charge-carrier transport processes and the passivation effect of carbazole further contributed to high V OC . The optimized 2,7-CzBP-treated device achieves the highest power conversion efficiency (PCE) of 25.88%, with V OC of 1.189 V for 0.090 cm 2 and the perovskite solar cell module with a PCE of 21.04% for 14 cm 2 . For 2,7-CzBP, the more extended conjugation and the more linear molecular geometry result in a more effective improvement in the performance. Organic additives with multiple functional groups have shown great promise in improving the performance and stability of perovskite solar cells. The functional groups can passivate undercoordinated ions to reduce nonradiative recombination losses. However, how these groups synergistically affect the enhancement beyond passivation is still unclear. Specifically, isomeric molecules with different substitution patterns or molecular shapes remain elusive in designing new organic additives. Here, we report two isomeric carbazolyl bisphosphonate additives, 2,7-CzBP and 3,6-CzBP. The isomerism effect on passivation and charge transport process was studied. The two molecules have similar passivation effects through multiple interactions, e.g., P = O···Pb, P = O···H–N and N–H···I. 2,7-CzBP can further bridge the perovskite crystallites to facilitates charge transport. Power conversion efficiencies (PCEs) of 25.88% and 21.04% were achieved for 0.09 cm 2 devices and 14 cm 2 modules after 2,7-CzBP treatment, respectively. The devices exhibited enhanced operational stability maintaining 95% of initial PCE after 1000 h of continuous maximum power point tracking. This study of isomerism effect hints at the importance of tuning substitution positions and molecular shapes for organic additives, which paves the way for innovation of next-generation multifunctional aromatic additives.

Inverted perovskite solar cells based on weakly polarized hole-transporting layers suffer from the problem of polarity mismatch with the perovskite precursor solution, resulting in a nonideal wetting surface. In addition to the bottom-up growth of the polycrystalline halide perovskite, this will inevitably worse the effects of residual strain and heterogeneity at the buried interface on the interfacial carrier transport and localized compositional deficiency. Here, we propose a multifunctional hybrid pre-embedding strategy to improve substrate wettability and address unfavorable strain and heterogeneities. By exposing the buried interface, it was found that the residual strain of the perovskite films was markedly reduced because of the presence of organic polyelectrolyte and imidazolium salt, which not only realized the halogen compensation and the coordination of Pb 2+ but also the buried interface morphology and defect recombination that were well regulated. Benefitting from the above advantages, the power conversion efficiency of the targeted inverted devices with a bandgap of 1.62 eV was 21.93% and outstanding intrinsic stability. In addition, this coembedding strategy can be extended to devices with a bandgap of 1.55 eV, and the champion device achieved a power conversion efficiency of 23.74%. In addition, the optimized perovskite solar cells retained 91% of their initial efficiency (960 h) when exposed to an ambient relative humidity of 20%, with a T80 of 680 h under heating aging at 65 °C, exhibiting elevated durability.

Halide perovskites are novel photovoltaic materials with soft ionic lattice that are continuously exposed to sunlight during operation. High-energy ultraviolet (UV) irradiation will cause halide ion oxidation within the perovskite layer, accelerating halide ion migration and component loss, which results in a marked degradation in the device's photovoltaic performance. Here, we introduce a 2,3-bis(2,4,5-trimethyl-3-thienyl) maleimide (BTTM) molecule capable of interconversion between UV and visible light into the perovskite structure, intensifying the light stability of the perovskite layer via ion anchoring. Meanwhile, the incorporation of BTTM promotes the growth of perovskite crystals and efficiently passivates defects within the perovskite film, significantly boosting the open-circuit voltage of the perovskite solar cells. This results in a power conversion efficiency increase from 22.07% to 24.71%. Under UV irradiation (365 nm), BTTM molecules mitigate the degradation of perovskite by suppressing the ion migration of iodide ions. After cumulative exposure to 5 kWh/m2 of continuous UV irradiation, BTTM-based devices retain over 90% of their initial power conversion efficiency, demonstrating significantly enhanced UV stability. This study offers a straightforward approach to UV protection, providing novel insights for the environmental application of perovskite solar cells under intense UV irradiation.

The organic-inorganic lead halide perovskite layer is a crucial factor for the high performance perovskite solar cell (PSC). We introduce CH 3 NH 3 Br in the precursor solution to prepare CH 3 NH 3 PbI 3−x Br x hybrid perovskite, and an uniform perovskite layer with improved crystallinity and apparent grain contour is obtained, resulting in the significant improvement of photovoltaic performance of PSCs. The effects of CH 3 NH 3 Br on the perovskite morphology, crystallinity, absorption property, charge carrier dynamics and device characteristics are discussed, and the improvement of open circuit voltage of the device depended on Br doping is confirmed. Based on above, the device based on CH 3 NH 3 PbI 2.86 Br 0.14 exhibits a champion power conversion efficiency (PCE) of 18.02%. This study represents an efficient method for high-performance perovskite solar cell by modulating CH 3 NH 3 PbI 3−x Br x film.

Perovskite solar cells (PSCs) are undergoing rapid development and the power conversion efficiency reaches 25.7% which attracts increasing attention on their commercialization recently. In this review, we summarized the recent progress of PSCs based on device structures, perovskite-based tandem cells, large-area modules, stability, applications and industrialization. Last, the challenges and perspectives are discussed, aiming at providing a thrust for the commercialization of PSCs in the near future.

A thin NiO layer (∼164 nm in thickness) is fabricated on the surface of TiO2 photoanode by a simple hydrothermal method. The TiO2/NiO photoanode prepared on the hydrothermal temperature of 100 °C (TiO2/NiO-100) shows enhancement of light-harvesting ability and excellent dye adsorption amount. Moreover, the intensity-modulated photovoltage spectroscopy, intensity-modulated photocurrent spectroscopy and electrochemical impedance spectroscopy measurements illustrate that the NiO layer makes the dye-sensitized solar cells (DSSCs) with TiO2/NiO photoanodes shorten electron transport time, lengthen electron lifetime and obtain a higher charge collection efficiency than that of DSSCs with TiO2 photoanodes. Hence, the TiO2/NiO photoanode can efficiently decrease the electron transport resistance and charge recombination action. The DSSCs with TiO2/NiO-100 have an improvement photovoltaic performance and can obtain a higher value of power conversion efficiency (8.93 ± 0.34%) than that of DSSCs with TiO2 photoanodes (8.17 ± 0.33%) under full sunlight illumination (100 mW cm−2, AM 1.5 G).

The polypyrrole (PPy) electrode is synthesized by chemical oxidative polymerization on fluorine-doped tin oxide glass. Then the ferrous sulfide (FeS) nanoparticles is formed during the PPy nanoparticles by immersing the PPy electrodes in fresh Na 2 S methanol solution (0.1 M) for 20 min. The synergistic effect of PPy and FeS nanoparticles make PPy/FeS CE possesses perfect transparency, good conductivity and excellent electrocatalytic activity for the reduction of triiodide/iodide. This would be attributed to improve the contact between counter electrode and electrolyte and enhance the collection and transmission of electrons. The transparent and high-efficiency PPy/FeS CE appears to be a potential candidate to the high cost and corrodible Pt CE of DSSCs. The dye-sensitized solar cells (DSSCs) based on PPy/FeS electrode can obtain a higher power conversion efficiency (PCE) of 7.48 % than that of DSSCs with pure PPy electrode (6.45 %) or Pt electrode (7.10 %) under full sunlight illumination (100 mW cm −2 , AM 1.5 G). Furthermore, the DSSC based on PPy/FeS electrode would obtain a high value of PCE (5.72 %) with back illumination.