Chiral‐induced spin selectivity is recently demonstrated in a range of spin‐dependent optoelectronics and electrochemistry. Herein, a new type of amorphous chiral tartaric acid‐FeNi coordination ...polymer fabricated by electrodeposition methods, achieving both high spin‐polarization and high electrocatalytic activity for oxygen evolution, is reported. Circular dichroism shows signature optical activity from the coordination polymer. Conductive atomic force microscopy measurements demonstrate a high spin polarization through the chiral electrocatalyst, which significantly suppresses the formation of hydrogen peroxide byproducts compared to the achiral ones. These chiral Fe‐Ni electrocatalysts exhibit a low overpotential of 205 and 280 mV to achieve 10 and 100 mA cm−2, respectively.
This study demonstrates a new type of chiral Fe‐Ni electrocatalyst for enhanced oxygen evolution reaction (OER) through spin control by chiral‐induced spin selectivity. A high spin‐polarized current is generated in chiral electrocatalyst that suppresses the formation of H2O2 byproduct. Chiral catalyst shows a low OER overpotential and exhibits a 35% increase of current density compared to the achiral ones.
We report a large area of millimeter-scale p-n junction damage caused by potential-induced degradation (PID) of lab-stressed crystalline-Si modules. Kelvin probe force microscopy results show ...electrical potential change across the junction, and a recovery was observed after heat treatment. Electron-beam induced current results support the large-area damage instead of local shunts and a much lower collected current for the affected junction area. Furthermore, secondaryion mass spectrometry indicates that the large-area damage correlates with sodium contamination. The consistent results shed new light on PID mechanisms to investigate that are essentially different than the widely reported local junction shunts.
Stacking solar cells with decreasing band gaps to form tandems presents the possibility of overcoming the single-junction Shockley-Queisser limit in photovoltaics. The rapid development of ...solution-processed perovskites has brought perovskite single-junction efficiencies >20%. However, this process has yet to enable monolithic integration with industry-relevant textured crystalline silicon solar cells. We report tandems that combine solution-processed micrometer-thick perovskite top cells with fully textured silicon heterojunction bottom cells. To overcome the charge-collection challenges in micrometer-thick perovskites, we enhanced threefold the depletion width at the bases of silicon pyramids. Moreover, by anchoring a self-limiting passivant (1-butanethiol) on the perovskite surfaces, we enhanced the diffusion length and further suppressed phase segregation. These combined enhancements enabled an independently certified power conversion efficiency of 25.7% for perovskite-silicon tandem solar cells. These devices exhibited negligible performance loss after a 400-hour thermal stability test at 85°C and also after 400 hours under maximum power point tracking at 40°C.
The open-circuit voltage (V
) deficit in perovskite solar cells is greater in wide-bandgap (over 1.7 eV) cells than in perovskites of roughly 1.5 eV (refs.
). Quasi-Fermi-level-splitting ...measurements show V
-limiting recombination at the electron-transport-layer contact
. This, we find, stems from inhomogeneous surface potential and poor perovskite-electron transport layer energetic alignment. Common monoammonium surface treatments fail to address this; as an alternative, we introduce diammonium molecules to modify perovskite surface states and achieve a more uniform spatial distribution of surface potential. Using 1,3-propane diammonium, quasi-Fermi-level splitting increases by 90 meV, enabling 1.79 eV perovskite solar cells with a certified 1.33 V V
and over 19% power conversion efficiency (PCE). Incorporating this layer into a monolithic all-perovskite tandem, we report a record V
of 2.19 V (89% of the detailed balance V
limit) and over 27% PCE (26.3% certified quasi-steady state). These tandems retained more than 86% of their initial PCE after 500 h of operation.
Organic‐inorganic hybrid two‐dimensional (2D) perovskites (n≤5) have recently attracted significant attention because of their promising stability and optoelectronic properties. Normally, 2D ...perovskites contain a monocation e.g., methylammonium (MA+) or formamidinium (FA+). Reported here for the first time is the fabrication of 2D perovskites (n=5) with mixed cations of MA+, FA+, and cesium (Cs+). The use of these triple cations leads to the formation of a smooth, compact surface morphology with larger grain size and fewer grain boundaries compared to the conventional MA‐based counterpart. The resulting perovskite also exhibits longer carrier lifetime and higher conductivity in triple cation 2D perovskite solar cells (PSCs). The power conversion efficiency (PCE) of 2D PSCs with triple cations was enhanced by more than 80 % (from 7.80 to 14.23 %) compared to PSCs fabricated with a monocation. The PCE is also higher than that of PSCs based on binary cation (MA+‐FA+ or MA+‐Cs+) 2D structures.
Triple whammy: Reported here is the fabrication of 2D perovskites (n=5) with triple cations. The resulting perovskites feature longer carrier lifetime, greater mobility, and higher conductivity. The efficiency of 2D perovskite solar cells (PSCs) with triple cations was enhanced by more than 80 % (from 7.80 to 14.23 %) compared to PSCs fabricated with a monocation. The efficiency is also higher than that of PSCs based on binary cation 2D structures.
Deep defect states of Cadmium Telluride deposited via close space sublimation and magnetron sputtering are evaluated via steady state and time resolved photoluminescence. Intensity dependent ...photoluminescence measurements for as-grown and cadmium chloride treated samples reveal the recombination mechanism associated with each transition. The as-grown sputtered film photoluminescence is weak with broad features while the close space sublimation film photoluminescence is comparatively bright and dominated by a deep donor acceptor pair recombination. Unlike excitonic or free-to-bound transitions, donor acceptor pair recombination exhibits a distance dependence that determines the distribution of transition energies and recombination rates. We measure the PL lifetime with respect to energy as a direct observation of the increasing donor acceptor pair recombination rate with decreasing donor-acceptor separation.
Wide-bandgap (∼1.7–1.8 eV) perovskite solar cells have attracted substantial research interest in recent years due to their great potential to fabricate efficient tandem solar cells via combining ...with a lower bandgap (1.1–1.3 eV) absorber (e.g., Si, copper indium gallium diselenide, or low-bandgap perovskite). However, wide-bandgap perovskite solar cells usually suffer from large open circuit voltage (Voc) deficits caused by small grain sizes and photoinduced phase segregation. Here, we demonstrate that in addition to large grain sizes and passivated grain boundaries, controlling interface properties is critical for achieving high Voc's in the inverted wide-bandgap perovskite solar cells. We adopt guanidinium bromide solution to tune the effective doping and electronic properties of the surface layer of perovskite thin films, leading to the formation of a graded perovskite homojunction. The enhanced electric field at the perovskite homojunction is revealed by Kelvin probe force microscopy measurements. This advance enables an increase in the Voc of the inverted perovskite solar cells from an initial 1.12 V to 1.24 V. With the optimization of the device fabrication process, the champion inverted wide-bandgap cell delivers a power conversion efficiency of 18.19% and sustains more than 72% of its initial efficiency after continuous illumination for 70 h without encapsulation. Additionally, a semitransparent device with an indium tin oxide back contact retains more than 88% of its initial efficiency after 100 h maximum power point tracking.
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•Guanidinium bromide treatment to tune the doping properties of perovskite films.•Formation of a graded perovskite homojunction enhances built-in electric field.•Enhancement of open-circuit voltage from 1.12 to 1.24 V after the treatment.•Inverted wide-bandgap perovskite solar cells deliver a maximum efficiency of 18.19%.
We located the electrical junction (EJ) of Cu(In, Ga)Se 2 (CIGS) and Cu 2 ZnSnSe 4 (CZTS) solar cells with ~20-nm accuracy using a scanning capacitance spectroscopy (SCS) technique. A procedure was ...developed to prepare the cross-sectional samples and grow critical high-quality insulating layers for the SCS measurement. We found that CIGS has a buried homojunction with the EJ located at ~40 nm inside the CIGS/CdS interface. An n-type CIGS was probed in the region 10-30 nm away from the interface. By contrast, the CZTS/CdS cells have a heterointerface junction with a shallower EJ (~20 nm) than CIGS. The EJ is ~20 nm from the CZTS/CdS interface, which is consistent with asymmetrical carrier concentrations of the p-CZTS and n-CdS in a heterojunction cell. The unambiguous determination of the junction locations helped explain the large open circuit voltage difference between the state-of-the-art devices of CIGS and CZTS.
We applied a novel analytical technique-nearfield transport imaging (TI)-to photovoltaic materials for charge-carrier transport mapping in nanometer-scale. We measured the diffusion length of a ...well-controlled gallium arsenide (GaAs) thin-film samples and it agrees well with the results calculated by time-resolved photoluminescence. We report for the first time on TI experiments on thin-film cadmium telluride, including the effective carrier diffusion length, as well as the first near-field imaging of the effect of a single small defect on carrier transport and recombination in a GaAs sample. Furthermore, by changing the scanning setup, we were able to do near-field cathodoluminescence (CL), and correlated the results with standard CL results. The TI technique shows great potential for high spatial resolution mapping transport properties in solar cell materials.
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