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The performance of perovskite photovoltaics is fundamentally impeded by the presence of undesirable defects that contribute to non-radiative losses within the devices. Although mitigating these losses has been extensively reported by numerous passivation strategies, a detailed understanding of loss origins within the devices remains elusive. Here, we demonstrate that the defect capturing probability estimated by the capture cross-section is decreased by varying the dielectric response, producing the dielectric screening effect in the perovskite. The resulting perovskites also show reduced surface recombination and a weaker electron-phonon coupling. All of these boost the power conversion efficiency to 22.3% for an inverted perovskite photovoltaic device with a high open-circuit voltage of 1.25 V and a low voltage deficit of 0.37 V (a bandgap ~1.62 eV). Our results provide not only an in-depth understanding of the carrier capture processes in perovskites, but also a promising pathway for realizing highly efficient devices via dielectric regulation. Performance of perovskite photovoltaics is greatly affected by undesirable defects that contribute to non-radiative losses. Here, the authors mitigate these losses by doping perovskite with KI to alter the dielectric response, thus defect capturing probability, resulting in inverted device with PCE of 22.3% and low voltage loss.

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.

Thermally evaporated C 60 is a near-ubiquitous electron transport layer in state-of-the-art p–i–n perovskite-based solar cells. As perovskite photovoltaic technologies are moving toward industrialization, batch-to-batch reproducibility of device performances becomes crucial. Here, we show that commercial as-received (99.75% pure) C 60 source materials may coalesce during repeated thermal evaporation processes, jeopardizing such reproducibility. We find that the coalescence is due to oxygen present in the initial source powder and leads to the formation of deep states within the perovskite bandgap, resulting in a systematic decrease in solar cell performance. However, further purification (through sublimation) of the C 60 to 99.95% before evaporation is found to hinder coalescence, with the associated solar cell performances being fully reproducible after repeated processing. We verify the universality of this behavior on perovskite/silicon tandem solar cells by demonstrating their open-circuit voltages and fill factors to remain at 1950 mV and 81% respectively, over eight repeated processes using the same sublimed C 60 source material. Notably, one of these cells achieved a certified power conversion efficiency of 30.9%. These findings provide insights crucial for the advancement of perovskite photovoltaic technologies towards scaled production with high process yield. Batch-to-batch reproducibility of device performances is crucial for perovskite photovoltaics moving towards industrialization. Here, the authors show that commercial as-received C 60 source materials may coalesce during repeated thermal evaporation processes, jeopardizing such reproducibility.

Traditional photothermal agents of indocyanine green (ICG) have poor stability, short circulation time, and poor brain permeability due to the blood—brain barrier (BBB), greatly impairing their therapeutic efficacy in glioblastoma (GBM). Herein, we develop a novel kind of SiNPs-based nanoprobes to bypass the BBB for photothermal therapy of GBM. Typically, the SiNPs-based nanoprobes are composed of the particle itself, the BBB-targeting ligand of glucosamine (G), and the therapeutic agent of ICG. We demonstrate that the as-synthesized nanoprobes could cross the BBB through glucose transporter-1 (GLUT1)-mediated transcytosis, followed by accumulation at GBM tissues in mice. Compared with free ICG, G-ICG-SiNPs show stronger stability (for example, the fluorescence intensity of G-ICG-SiNPs loaded with the same dose of ICG decays by 34.6% after 25 days of storage, while the fluorescence intensity of ICG decays by 99.5% under the same conditions). Furthermore, the blood circulation time of G-ICG-SiNPs increases by about 17.3-fold compared with their ICG counterparts. After injection of the therapeutic agents into the GBM-bearing mice, GBM-surface temperature rises to 45.3 °C in G-ICG-SiNPs group after 5-min 808 nm irradiation but climbs only to 36.1 °C in equivalent ICG group under the identical conditions, indicating the superior photothermal effects of G-ICG-SiNPs in vivo .

Metal halide perovskites, owing to their straightforward bandgap tuning through variations in halide stoichiometry, have demonstrated significant potential in various optoelectronic devices. However, unwanted halide segregation under operational conditions, such as light illumination and voltage bias, limits practical applications, and the underlying mechanisms still require in-depth investigation. In this thesis, we experimentally explore both voltage-induced and light-induced halide segregation to uncover the photoelectrochemical origins of this phenomenon. We start with an examination of voltage-induced halide segregation and study the impact of voltage bias on halide perovskite devices. Through conducting a series of prolonged voltage biasing tests, complemented by extensive characterization techniques, we identify various voltage thresholds in mixed-halide perovskite devices and directly visualize the voltage-induced halide redistribution. Furthermore, we show that monolithic perovskite/silicon tandem solar cells exhibit superior reverse-bias resilience compared to perovskite single-junction devices, positioning them at a higher technology readiness level for addressing the challenge of partial shading. Lastly, we delve into light-induced halide segregation and examine the effect of organic hole transport layers (HTLs) on the photoluminescence behavior at perovskite/organic HTL interfaces. We demonstrate that the highest occupied molecular orbital energy of the HTL influences the reactivity of the I2/HTL redox reaction, halogen diffusion, and light-induced halide segregation at these interfaces. Our findings offer new insights into a variety of voltage-induced and light-induced instabilities in halide perovskite materials and devices from a photoelectrochemical standpoint, guiding the development of perovskite-based optoelectronic devices towards stable operation.

Abstract The performance of perovskite photovoltaics is fundamentally impeded by the presence of undesirable defects that contribute to non-radiative losses within the devices. Although mitigating these losses has been extensively reported by numerous passivation strategies, a detailed understanding of loss origins within the devices remains elusive. Here, we demonstrate that the defect capturing probability estimated by the capture cross-section is decreased by varying the dielectric response, producing the dielectric screening effect in the perovskite. The resulting perovskites also show reduced surface recombination and a weaker electron-phonon coupling. All of these boost the power conversion efficiency to 22.3% for an inverted perovskite photovoltaic device with a high open-circuit voltage of 1.25 V and a low voltage deficit of 0.37 V (a bandgap 1.62 eV). Our results provide not only an in-depth understanding of the carrier capture processes in perovskites, but also a promising pathway for realizing highly efficient devices via dielectric regulation.

Thermally evaporated C is a near-ubiquitous electron transport layer in state-of-the-art p-i-n perovskite-based solar cells. As perovskite photovoltaic technologies are moving toward industrialization, batch-to-batch reproducibility of device performances becomes crucial. Here, we show that commercial as-received (99.75% pure) C source materials may coalesce during repeated thermal evaporation processes, jeopardizing such reproducibility. We find that the coalescence is due to oxygen present in the initial source powder and leads to the formation of deep states within the perovskite bandgap, resulting in a systematic decrease in solar cell performance. However, further purification (through sublimation) of the C to 99.95% before evaporation is found to hinder coalescence, with the associated solar cell performances being fully reproducible after repeated processing. We verify the universality of this behavior on perovskite/silicon tandem solar cells by demonstrating their open-circuit voltages and fill factors to remain at 1950 mV and 81% respectively, over eight repeated processes using the same sublimed C source material. Notably, one of these cells achieved a certified power conversion efficiency of 30.9%. These findings provide insights crucial for the advancement of perovskite photovoltaic technologies towards scaled production with high process yield.

Indoleamine 2, 3-dioxygenases (IDO1 and IDO2) and tryptophan 2, 3-dioxygenase (TDO) are tryptophan catabolic enzymes that catalyze the conversion of tryptophan into kynurenine. The depletion of tryptophan and the increase in kynurenine exert important immunosuppressive functions by activating T regulatory cells and myeloid-derived suppressor cells, suppressing the functions of effector T and natural killer cells, and promoting neovascularization of solid tumors. Targeting IDO1 represents a therapeutic opportunity in cancer immunotherapy beyond checkpoint blockade or adoptive transfer of chimeric antigen receptor T cells. In this review, we discuss the function of the IDO1 pathway in tumor progression and immune surveillance. We highlight recent preclinical and clinical progress in targeting the IDO1 pathway in cancer therapeutics, including peptide vaccines, expression inhibitors, enzymatic inhibitors, and effector inhibitors.