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There exists a considerable density of interaggregate grain boundaries (GBs) and intra-aggregate GBs in polycrystalline perovskites. Mitigation of intra-aggregate GBs is equally notable to that of interaggregate GBs as intra-aggregate GBs can also cause detrimental effects on the photovoltaic performances of perovskite solar cells (PSCs). Here, we demonstrate full-scale GB mitigation ranging from nanoscale intra-aggregate to submicron-scale interaggregate GBs, by modulating the crystallization kinetics using a judiciously designed brominated arylamine trimer. The optimized GB-mitigated perovskite films exhibit reduced nonradiative recombination, and their corresponding mesostructured PSCs show substantially enhanced device efficiency and long-term stability under illumination, humidity, or heat stress. The versatility of our strategy is also verified upon applying it to different categories of PSCs. Our discovery not only specifies a rarely addressed perspective concerning fundamental studies of perovskites at nanoscale but also opens a route to obtain high-quality solution-processed polycrystalline perovskites for high-performance optoelectronic devices.

In the commercial development of perovskite solar cells, the main challenge lies in achieving efficient devices with high stability. Additive engineering in polycrystalline perovskites is considered as an effective approach to address this challenge by passivating surface defects and reducing carrier losses associated with these defects. In this work, the passivation effect of molecules with different side chain groups on perovskites and the role of binding energy in mitigating carrier loss are studied. The findings reveal that the thiophene group is particularly effective in passivating defects and enhancing hole transport. Consequently, devices treated with 2‐thienylmethylamine hydrochloride (TMAC) demonstrate a champion power conversion efficiency (PCE) of 24.63%. Furthermore, these TMAC‐treated devices exhibit remarkable stability, maintaining over 93.13% of their initial efficiencies after 1200 h of continuous illumination under maximum power point tracking (MPPT). This research presents a pathway to enhance the optoelectronic performance and stability of perovskite solar cells. [ABSTRACT FROM AUTHOR]

The buried interface between the electron transport layer (ETL) and the perovskite layer plays a crucial role in enhancing the power conversion efficiency (PCE) and stability of n–i–p type perovskite solar cells (PSCs). In this study, the interface between the chemical bath deposited (CBD) titanium oxide (TiO2) ETL and the perovskite layer using multi‐functional potassium trifluoromethyl sulfonate (SK) is modified. Structural and elemental analyses reveal that the trifluoromethyl sulfonate serves as a crosslinker between the TiO2 and the perovskite layer, thus improving the adhesion of the perovskite to the TiO2 ETL through strong bonding of the ─CF3 and ─SO3− terminal groups. Furthermore, the multi‐functional modifiers reduced interface defects and suppressed carrier recombination in the PSCs. Consequently, devices with a champion PCE of 25.22% and a fill factor (FF) close to 85% is achieved, marking the highest PCE and FF observed for PSCs based on CBD TiO2. The unencapsulated device maintained 81.3% of its initial PCE after operating for 1000 h. [ABSTRACT FROM AUTHOR]

Solar fuels offer a promising approach to provide sustainable fuels by harnessing sunlight1,2. Following a decade of advancement, Cu2O photocathodes are capable of delivering a performance comparable to that of photoelectrodes with established photovoltaic materials3–5. However, considerable bulk charge carrier recombination that is poorly understood still limits further advances in performance6. Here we demonstrate performance of Cu2O photocathodes beyond the state-of-the-art by exploiting a new conceptual understanding of carrier recombination and transport in single-crystal Cu2O thin films. Using ambient liquid-phase epitaxy, we present a new method to grow single-crystal Cu2O samples with three crystal orientations. Broadband femtosecond transient reflection spectroscopy measurements were used to quantify anisotropic optoelectronic properties, through which the carrier mobility along the [111] direction was found to be an order of magnitude higher than those along other orientations. Driven by these findings, we developed a polycrystalline Cu2O photocathode with an extraordinarily pure (111) orientation and (111) terminating facets using a simple and low-cost method, which delivers 7 mA cm−2 current density (more than 70% improvement compared to that of state-of-the-art electrodeposited devices) at 0.5 V versus a reversible hydrogen electrode under air mass 1.5 G illumination, and stable operation over at least 120 h.A study introduces a novel method to grow single-crystal Cu2O thin films with selected crystal orientations, highlighting enhanced bulk carrier mobility and carrier diffusion length along the [111] direction that yields Cu2O photocathodes with improved performance. [ABSTRACT FROM AUTHOR]

Antimony selenosulfide (Sb2(S,Se)3) solar cells bear great potential for sustainable photovoltaic technology, attributed to their excellent semiconductor properties. Despite the encouraging breakthroughs, the efficiency of Sb2(S,Se)3 solar cells still leaves much room for improvement due to the large open‐circuit voltage (VOC) deficit (the radiative VOC limit minus the high VOC). Herein, ammonium sulfide ((NH4)2S) solution is utilized to treat Sb2(S,Se)3 films to tailor their surface properties. The disappearance of the hole defect (H1) and the decrease of the defect concentration of hole defect (H2) confirm that non‐radiative recombination is suppressed greatly. Photovoltage decay lifetime is greatly increases from 67.9 to 297.9 µs. The upshifted valence band maximum optimizes the energy level alignment between the p–n heterojunction, enhancing the carrier transport. Remarkably, this treatment yields a record lowest VOC deficit of 0.49 V by now, and the best device with 10.41% efficiency, ca. 25% improvement over the control device (8.35%). This study provides valuable insight into reducing the VOC deficit in solar cells and related photoelectronic devices by minimizing non‐radiative recombination, and also presents a great potential strategy to achieve the lowest VOC deficit. [ABSTRACT FROM AUTHOR]