Structural and optical properties of Ti and Cu co‐doped ZnO thin films for photovoltaic applications of dye sensitized solar cells

This article investigates thermal laser separation (TLS) on p -type Czochralski-grown silicon (Cz-Si) passivated emitter and rear cells (PERC) and n -type Cz-Si heterojunction (SHJ) solar cells. The TLS comprises of two laser-based processes: the crack initiation by a scribe laser and the crack propagation by a cleave process leading to separated cells with smooth edge surfaces. The sole impact of the cleave process on the cells’ passivation layers is examined by performing it without the initial scribe, not separating the samples. By means of photoluminescence imaging, different cleave laser powers P C on passivated PERC and SHJ cell precursors are investigated, and the optimum P C values are then chosen for the processing of metallized and fired host cells with half cell and shingle cell layouts. Both, the cleave process as well as the complete TLS process are then separately performed in order to investigate the effect of each individual process by Suns V OC measurements taken before and after processing. For monofacial PERC cells, a drop in pseudofill factor Δ pFF = – 0.3%abs is recorded after TLS of the host cell into five shingle cells with 31.35 mm cell width. The effect on bifacial SHJ cells is stronger with Δ pFF = – 2.1%abs. Thereby, the cleave process itself does not induce significant losses in the cell performance for both cell types. The main losses are attributed to the recombination at the newly created unpassivated edges after complete TLS.

Thermal Laser Separation of PERC and SHJ Solar Cells

Minimizing the optical parasitic absorption loss in hydrogenated amorphous silicon (a‐Si:H) and transparent conductive oxide (TCO) layers is considered an effective approach to further improve the power conversion efficiencies (PCEs) of crystalline silicon heterojunction (SHJ) solar cells. In this work, carrier‐selective passivating contacts for both polarities, e.g., alkali fluoride/aluminum electron‐selective contact and transition metal oxide/silver hole‐selective contact, are used to completely replace the doped a‐Si:H layers in SHJ solar cell, forming a totally TCO‐ and dopant‐free asymmetric structure. By minimizing the charge carrier transporting and recombination losses on the front‐side electron‐selective contact through interface engineering, an improved photovoltaic performance with a short‐circuit current density of 40.5 mA cm−2, an open‐circuit voltage of 0.709 V, and a fill factor of 79.6% is realized, resulting in a final PCE exceeding 22.9%. The successful demonstration of this work provides an effective way to further boost the efficiency, as well as reduce the cost of SHJ solar cells with a TCO‐free and doped a‐Si:H‐free configuration, using a moderate and simplified fabrication process.

Enabling Transparent‐Conductive‐Oxide Free Efficient Heterojunction Solar Cells by Flexibly Using Dopant‐Free Contact

Unlocking the full potential of passivating contacts, increasingly popular in the silicon solar cell industry, requires determining the minority carrier lifetime. Minor passivation drops limit the functioning of solar cells; however, they are not detected in devices with open-circuit voltages below 700 mV. In this work, simulations and experiments were used to show the effect of localized surface defects on the overall device performance. Although the defects did not significantly affect lifetime measurements prior to electrode deposition or open-circuit voltage measurements at standard-test conditions, they had a significant impact on the point of operation and, in turn, device efficiency (up to several percent efficiency drop). Furthermore, this study demonstrates that localized defects can have a detrimental effect on well-passivated areas located several centimeters away through electrical connection by the electrode. This leads to a low-injection lifetime drop after electrode deposition. Thus, commonly measured lifetime curves before metallization (and therefore internal voltage) are usually not representative of their respective values after metallization. The low-injection lifetime drop often observed after electrode deposition can be derived from such local surface defects and not from a homogeneous passivation drop.

Influence of local surface defects on the minority-carrier lifetime of passivating-contact solar cells

Illumination-Dependent Temperature Coefficients of the Electrical Parameters of Modern Silicon Solar Cell Architectures

Analysis of edge losses on silicon heterojunction half solar cells

Today, an increasing number of companies are working with heterojunction technology because of its higher efficiency potential and decreasing LCOEs compared to traditional solar cells [1] [2]. One of the major challenges for SHJ solar cells is the use of low temperature silver paste for metallization because of 1) their lower conductivity and 2) their need of alternative interconnection strategies as described by Faes et. al. [2]. As heterojunction technology is relatively new and as new wafer sizes are about to be adopted, metallization and interconnection are facing challenges and opportunities [3]. To screen quickly the multiple possibilities, a specific modelling for heterojunction has to be developed. The parameters describing the metallization and interconnection of a module are numerous and highly interdependent. In this field, performance optimization is always a compromise to be made mainly between the additional series resistance of the elements (TCO, finger, busbar, ribbons) and their impact on the photo-generated current. Optimal results are expressed in term of finger width, grid pitch, number of busbar and ribbons, section of ribbons, etc. Even under standard conditions (STC), the optimizations are obviously dependent on the parameters of the non-metallized cell. Also, the results differ whether the optimization criterions include the cost of the individual elements (€/Wp). For these reasons, CTMOD, a multidimensional prediction model of the performance and material cost of each possible architecture, is essential.

CTMOD: A cell-to-module modelling tool applied to optimization of metallization and interconnection of high-efficiency bifacial silicon heterojunction solar module

http://manuscript.elsevier.com/S0927024822001386/pdf/S0927024822001386.pdf

Characterization of UV–Vis–NIR optical constants of encapsulant for accurate determination of absorption and backscattering losses in photovoltaics modules

The use of half-cells is known to be an effective way to increase cell-to-module (CTM) ratio, thanks to lower resistive losses. Multi-wire interconnection allows reducing silver paste consumption; offering better effective shading compared to flat ribbons. The number and the diameter of wires influence the series resistance and photo-generated current values in opposite ways, leading to an optimal value in CTM. In this paper, the impact of grid resistance and effective shading of wires on the optimum number and diameter of wires is evaluated. Two module architectures are considered, halfand full-cells. Decreasing grid resistance by a factor two, even if it allows using fewer wires, has only a small impact on CTM gain (+ 0.3 %). A large range of possible values of effective shading is found in the literature. The sensitivity analysis shows that it has a major impact on CTM (± 1.3 %), at constant consumption in amount of wires. The use of halfcells allows to employ less wires with a smaller diameter than in full-cell modules. It is a double gain, in CTM performance (+ 2.2 %) and in consumption of raw material (40 %).

https://hal.archives-ouvertes.fr/hal-01895240/document

Julien Eymard

Papers

Analysis of edge losses on silicon heterojunction half solar cells

CTMOD: A cell-to-module modelling tool applied to optimization of metallization and interconnection of high-efficiency bifacial silicon heterojunction solar module

Characterization of UV–Vis–NIR optical constants of encapsulant for accurate determination of absorption and backscattering losses in photovoltaics modules

Performance simulations of a 72-cell, a-si het module with different tab-interconnection geometries

Performance of two-flux and four-flux models for predicting the spectral reflectance and transmittance factors of flowable dental resin composites.