Simulation-based Efficiency Gain Analysis of 21.2%-efficient Screen-printed PERC Solar Cells

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We demonstrate a procedure for quantifying efficiency gains that treats resistive, recombinative, and optical losses on an equal footing. For this, we apply our conductive boundary model as implemented in the Quokka cell simulator. The generation profile is calculated with a novel analytical light-trapping model. This model parameterizes the measured reflection spectra and is capable of turning the experimental case gradually into an ideal Lambertian scheme. Simulated and measured short-circuit current densities agree for our 21.2%-efficient screen-printed passivated emitter and rear cell and for our 23.4%-efficient ion-implanted laser-processed interdigitated back-contacted cell. For the loss analysis of these two cells, we set all experimentally accessible control parameters (e.g., saturation current densities, sheet resistances, and carrier lifetimes) one at a time to ideal values. The efficiency gap to the ultimate limit of 29% is thereby fully explained in terms of both individual improvements and their respective synergistic effects. This approach allows comparing loss structures of different types of solar cells, for example, passivated emitter and rear cell and interdigitated back-contacted cells. Copyright

“…The emitter has a sheet resistance of 75 Ω and a saturation current density of 100 fA/cm 2 in the non‐metalized region. These and more data were reported in .…”

Section: Cells Investigatedmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Breakdown of the efficiency gap to 29% based on experimental input data and modeling

Brendel

Dullweber

Peibst

et al. 2015

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“…Record efficiencies up to 22.1% have been reported for industrial‐type PERC cells . However, with the strongly reduced carrier recombination at the PERC cells rear side, the conversion efficiency of industrial p‐type PERC cells is mainly limited by the high emitter saturation current density J 0E of around 90 fA/cm 2 of conventional homogeneously POCl 3 diffused emitters . In this paper we investigate two alternative emitter formation technologies which both strongly reduce the phosphorus surface concentration thereby decreasing Shockley–Read–Hall and Auger recombination.…”

Section: Introductionmentioning

confidence: 99%

Emitter saturation current densities of 22 fA/cm² applied to industrial PERC solar cells approaching 22% conversion efficiency

Dullweber

Hannebauer

Dorn

et al. 2016

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Passivated Emitter and Rear Cells (PERC) are currently being introduced into mass production. The conversion efficiency of industrial p-type PERC cells is limited by the emitter saturation current density of around 90 fA/cm 2 of conventional homogeneously POCl 3 diffused emitters. In this paper we investigate two alternative emitter formation technologies. The first approach named in-situ oxidation inserts a short thermal oxidation in-between the phosphorus silicate glass deposition and the drive-in of a conventional homogeneous POCl 3 diffusion thereby reducing the phosphorus surface concentration. The second approach named Gas Phase Etch Back (GEB) selectively removes around 40 nm of the highly doped surface of the POCl 3 diffused emitter by the reactive gas phase of the wet chemical rear polishing bath. Whereas the conventional POCl 3 emitter exhibits a phosphorus surface doping concentration of 3 × 10 20 cm À3 , the in-situ oxidation and the GEB process reduce the doping concentration to 7 × 10 19 cm À3 and 4 × 10 19 cm À3 , respectively. Accordingly, the emitter saturation current density is reduced to excellent values of 22 fA/cm 2 (in-situ oxidation) and 28 fA/cm 2 (GEB) compared with 89 fA/cm 2 for the reference POCl 3 diffusion. Whereas the reference POCl 3 emitter limits the PERC conversion efficiency η to 21.1% and the open circuit voltage V oc to 655 mV, the in-situ oxidation improves the PERC current-voltage parameters up to 21.3% and 663 mV. The highest efficiency of 21.6% is obtained with the selective GEB emitter. When solving series resistance issues with the most advanced GEB emitter, the measured V oc and J sc values would support PERC conversion efficiencies up to 21.9%.

“…19 The second constraint, the carrier recombination at the metalsemiconductor contacts, also limits the overall performance of c-Si solar cells with standard absorber thicknesses ($180 μm). 20 In order to constrict this limitation, c-Si solar cells with PERC designs on ptype wafers were developed reaching efficiencies above 23%. 21 In this design, the rear side is passivated by dielectric layers where metal contacts are locally contacting the underlying Si.…”

mentioning

confidence: 99%

Fourteen percent efficiency ultrathin silicon solar cells with improved infrared light management enabled by hole‐selective transition metal oxide full‐area rear passivating contacts

Nasser

Borra

Ciftpinar

et al. 2021

The present study investigates the application of hole‐selective transition metal oxide (TMO) layers (MoOx, V2Ox, and WOx) with silver (Ag) as full‐area rear contact to 22.5 μm‐thick low‐quality Cz p‐type c‐Si solar cells. Thin films of metal oxides are deposited directly on p‐type c‐Si by thermal evaporation at room temperature. The large work function of these TMOs creates strong accumulation at the interface with p‐type c‐Si, which allows only holes to transport and simultaneously suppress the interfacial recombination current density (J0) and contact resistivity (ρc). The current generation and losses of 22.5 μm‐thick solar cells with different hole‐selective TMO/Ag at the rear are simulated. The presence of TMO/Ag at the rear is found to significantly reduce parasitic light absorption at longer wavelengths which becomes more pronounced for ultrathin wafers, providing significant advantages over conventional Al contact. The best device performance was attained by the MoOx/p‐type c‐Si solar cells, demonstrating a considerably high efficiency (η) of 14% with Voc of 555 mV, FF of 76.0%, and Jsc of 33.2 mA/cm2. Furthermore, the present work is the first to employ MoOx, V2Ox, and WOx as rear contact in ultrathin p‐type c‐Si solar cells.