Progress in Photovoltaics最新文献

Tunnel oxide passivating contacts with boron-doped polysilicon (i.e., p-type TOPCon) hold substantial potential for application in the devices with higher efficiency, that is, back-junction (BJ) or all-back-contact (BC) solar cells. However, achieving excellent passivation for p-type TOPCon remains a challenge. In this study, we propose a two-step oxidation (TSO) method using low-temperature oxidated silicon oxide (SiO_x) with a post-nitrous oxide/hydrogen plasma (N₂O/H₂) treatment to prepare high-quality ultrathin SiO_x and achieve highly passivated p-type TOPCon. Through optimization of plasma treatment pressure and annealing conditions, we achieve excellent passivation and contact properties of double-sided p-type TOPCon, with an implied open-circuit voltage (iV_oc) of 740 mV, marking the highest publicly reported value for p-type TOPCon. Additionally, we achieve a single-sided saturation recombination current density (J_0,s) of 4.0 fA/cm² and a contact resistivity of 22 mΩ cm². Semi-finished back-junction solar cell incorporating TSO-SiO_x exhibits excellent passivation performance with an iV_oc of 744 mV, demonstrating the feasibility of device applications. The two-step oxidation method proposed in this work enhances the passivation performance of p-type TOPCon, offering a technique with significant potential for industrial applications in preparing high-quality p-type TOPCon.

Current leakage through localized stacked structures, comprising opposite types of carrier-selective transport layers, is a prevalent issue in silicon-based heterojunction solar cells. Nevertheless, the behavior of this leakage region remains unclear, leading to a lack of guidance for structural design, material selection and process sequence control, thereby causing fluctuations of device performance. This study elucidates current-voltage characteristics, influential factors, and underlying carrier transport mechanism of the leakage region with different stacking sequences and explores their impact on various configurations of solar cells. Characteristics of the leakage region resembling Esaki diodes or reverse diodes are revealed, along with the bias conditions of the leakage region at different locations across the solar cell. The findings suggest that modulating the behavior of the leakage region is feasible for improving device performance or serving specific purposes. This work provides guidance for the design and assessment of current leakage in the edge region of front and back contact cells, in the gap region of conventional back-contacted cells, as well as in the tunneling region of tunneling back-contacted cells and tandem cells.

The use of single-layer polysilicon (poly-Si) in tunnel oxide passivated contact (TOPCon) structures has demonstrated excellent passivation and contact performance. However, commercial TOPCon solar cell fabrication requires screen-printing and cofiring techniques for electrode preparation. The single-layer structure is less efficient at preventing metal atoms in the electrode paste from penetrating the silicon bulk. Furthermore, the uniformity of doping concentration and crystallinity within this structure poses challenges as it fails to optimally meet the intricate requirements for achieving superior performance in terms of passivation, contact, and mitigating parasitic absorption. In this study, the deposition process of the amorphous silicon (a-Si) precursor layer using an in-line magnetron sputtering system incorporated an additional plasma oxidation step, resulting in a bilayer poly-Si structure with the newly introduced SiO_x acting as a partition. Detailed investigations were conducted into the passivation quality, contact resistivity, crystallinity, and the distribution of critical atoms in the bilayer structure. Subsequently, the bilayer configuration was utilized in the manufacturing process of TOPCon solar cells. These efforts resulted in a notable enhancement in open-circuit voltage (V_oc) and short-circuit current (I_sc), leading to a 0.06% efficiency improvement, based on the average performance of ~200 cells per group.

The poor crystal quality inside an absorber layer and the presence of various harmful defects are the main obstacles restricting the properties of Cu₂ZnSn (S, Se)₄ (CZTSSe) thin-film solar cells. Cation doping has attracted considerable research attention as a viable strategy to overcome this challenge. In this paper, based on Sb-substituted CZTSSe system, we prove that Ag partially substituting Cu may be a feasible strategy. After a series of characterization of the films, it was discovered that the crystal quality and crystallinity of the films were further improved by introducing Ag into Cu₂Zn(Sb, Sn) (S, Se)₄ (CZTSSSe), and the concentrations of Cu_Zn accepter defects and 2[Cu_Zn + Sn_Zn] defect clusters were effectively inhibited. At the same time, the carrier concentration is increased. The results show that when the Ag doping ratio is 15%, the photovoltaic conversion efficiency (PCE) reaches 8.34%, compared with the single-doped Sb element, the efficiency is increased by 24%. For the first time, this study investigates the collaborative effect of Sb, Ag dual-cation substitution in CZTSSe. The solar cell performance enhancement mechanism offers new potential for the advancement of CZTSSe thin-film solar cell technology in the future.

Over the past decade, silicon solar cells with carrier-selective passivating contacts based on polysilicon capping an ultra-thin silicon oxide (commonly known as TOPCon or POLO) have demonstrated promising efficiency potentials and are regarded as an evolutionary upgrade to the PERC (passivated emitter and rear contact) cells in manufacturing. The polysilicon-based passivating contacts also exhibit excellent gettering effects that relax the wafer and cleanroom requirements to some extent. In this work, we experimentally explore the impact of bulk iron contamination and polysilicon gettering on the passivation quality of the polysilicon/oxide structure and the resulting solar cells performance. Results show that both n- and p-type polysilicon/oxide passivating contacts are not affected by iron gettering, demonstrating robust and stable passivation quality. However, for a very high bulk iron contamination (1 × 10¹³ cm⁻³), the accumulated iron in the p-type lightly boron-doped emitter in crystalline silicon would degrade the emitter saturation current density. This can cause a reduction in both open-circuit voltage and short-circuit current. Meanwhile, this very high iron content (1 × 10¹³ cm⁻³) can further degrade the fill factor and temperature coefficient of the cells. On the other hand, for an initial iron content of 2 × 10¹² cm⁻³, which should be well above the iron level in the current industrial Czochralski silicon wafers, the resulting cells demonstrate similar performance as the control group with no intentional iron contamination. This work brings attention to both the benefits of polysilicon gettering effects as well as the potential degradation due to the accumulation of metal impurities in the p-type emitter region.

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since July 2024 are reviewed.