Heterojunction (HJ) crystalline silicon (c‐Si) solar cells outstanding performance relies heavily on the excellent passivation provided by the amorphous Si (a‐Si:H) layer. However, recombination at ...the a‐Si:H/c‐Si interface can vary over time and become particularly detrimental for HJ modules performance making the full understanding of the recombination mechanisms at play of paramount importance. In this work, the variation of effective lifetime for high‐quality n‐type FZ c‐Si substrates coated with a‐Si:H(i) layer after several processing steps and over a period of 28 months is tracked. The root cause for degradation is identified by experimentally evaluating the surface recombination velocity (SRV) temperature‐ and injection‐dependence before and after degradation has occurred. By applying a model for the recombination at the a‐Si:H/c‐Si interface to temperature‐ and injection‐dependent SRV data, the authors are able to assess the lifetime decay as entirely ascribed to a loss of chemical passivation. Upon re‐annealing the samples, only a partial recovery of lifetime is obtained suggesting that effusion of hydrogen from the a‐Si:H layer has occurred. These results indicate that the usage of a capping layer is needed whereas a thorough engineering of the a‐Si:H(i) layer thickness may be necessary to avoid the loss of performance of a‐Si based heterojunction structures and modules.
The degradation of heterojunction solar cells is a problematic aspect of a technology otherwise extremely promising for the future of PV. In this work, the authors experimentally evaluate the quality of surface passivation before and after degradation and demonstrate that its root cause is the partial effusion of hydrogen from the a‐Si(i) layer.
Tin monosulfide (SnS) is of interest as a potential solar cell absorber material. We present a preliminary investigation of the effects of sputtering conditions on SnS thin-film structural, optical, ...and electronic properties. Films were RF sputtered from an SnS target using an argon plasma. Resistivity, stoichiometry, phase, grain size and shape, bandgap, and optical absorption coefficient can be varied by modifying argon pressure for a fixed deposition time. Most films have an indirect bandgap in the range of 1.08–1.18
eV. XRD patterns confirmed the films as mostly crystalline, and grain morphology was examined using profile and surface SEM images.
Hybrid organometal halide perovskites are known for their excellent optoelectronic functionality as well as their wide‐ranging chemical flexibility. The composition of hybrid perovskite devices has ...trended toward increasing complexity as fine‐tuned properties are pursued, including multielement mixing on the constituents A and B and halide sites. However, this tunability presents potential challenges for charge extraction in functional devices. Poor consistency and repeatability between devices may arise due to variations in composition and microstructure. Within a single device, spatial heterogeneity in composition and phase segregation may limit the device from achieving its performance potential. This review details how the nanoscale elemental distribution and charge collection in hybrid perovskite materials evolve as chemical complexity increases, highlighting recent results using nondestructive operando synchrotron‐based X‐ray nanoprobe techniques. The results reveal a strong link between local chemistry and charge collection that must be controlled to develop robust, high‐performance hybrid perovskite materials for optoelectronic devices.
Hybrid halide perovskite thin films exhibit complex chemistry at the nanoscale that can affect their optoelectronic performance. In situ characterization of chemistry and functionality, such as by operando X‐ray fluorescence and X‐ray beam induced current measurements of perovskite solar cells, reveals insights into the relationship between local current collection, nonstoichiometry, and chemistry composition in hybrid lead perovskite absorbers.
Temperature‐ and injection‐dependent lifetime spectroscopy (TIDLS) is extensively used for the characterization of defects in silicon material for photovoltaic applications. By coupling TIDLS ...measurements with Shockley–Read–Hall recombination models, the most important defects’ parameters can be assessed including the defect energy level Et and the capture cross section ratio k. However, while proving extremely helpful in a variety of studies aiming at the characterization of contaminated silicon, a generalized approach for the analysis of industrially‐relevant material has not yet emerged. In this contribution, we examine in detail the recently introduced defect parameters contour mapping (DPCM) methodology for TIDLS data analysis as a tool for direct visualization of possible lifetime limiting defects. Herein, we showcase the DPCM method's potential by applying it to two representative case studies selected from literature and we demonstrate that, even when data are scarce, invaluable information is obtained in an easy and intuitive way without any a priori assumption needed. We then apply the DPCM method to simulated TIDLS data to evaluate the general characteristics of its response and the optimal conditions for its application. This analysis proves that the temperature dependence of lifetime is the most critical information required toward a really univocal identification of metal impurities.
The correct identification of lifetime limiting impurities in silicon for photovoltaic application is often a problematic task, despite the many characterization techniques available. In this work, Bernardini et al. demonstrate that lifetime spectroscopy coupled with the Defect Parameters Contour Mapping approach greatly simplifies this task and represents a powerful tool applicable to many experimental scenarios.
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