Recombination Current Density Research Articles

Pre-annealing for improved LPCVD deposited boron-doped poly-Si hole-selective contacts

We demonstrate the beneficial effect of a pre-annealing step prior to the boron diffusion on passivation and contact resistivity of industrially LPCVD deposited poly-Si/SiOX hole-selective contacts. We investigate the influence of the pre-annealing temperature on passivation quality, measured as implied open-circuit voltage and recombination current density, and on changes in crystallinity, characterized by Raman spectroscopy. A clear increase in passivation quality is observed on planar and textured surfaces as well as for various poly-Si thicknesses (100–230 nm) and thermal SiOX growth temperatures (600–800 °C). On planar surfaces and without the use of atomic hydrogenation, we report an increase in iVOC of around 5 mV with every additional increase of pre-annealing temperature by 50 °C (>900 °C) leading to an iVOC of 720 mV (J0 = 9.3 fA/cm2). After atomic hydrogenation, the effect of the pre-annealing is less pronounced. Nevertheless a gain in iVOC (reduction in J0) of 5–10 mV (2–5 fA/cm2) is achieved when comparing samples without pre-annealing with samples after a pre-annealing at 1050 °C. On textured surfaces on the other hand, this trend is more pronounced after atomic hydrogenation, for which a pre-crystallisation at 1050 °C leads to an iVOC (J0) of 705 mV (16.8 fA/cm2), which is a gain (reduction) of 24 mV (21.7 fA/cm2) compared to samples without a pre-annealing step.

Analysis of variation in recombination characteristics due to light and heat in industrial silicon solar cells

This work presents a comprehensive analysis of the variation in performance parameters of monocrystalline and multicrystalline silicon solar cells when subjected to illumination at elevated temperature. Higher degradation and better regeneration in performance parameters namely open circuit voltage (VOC), short circuit current density (JSC) and fill factor (FF) are observed for monocrystalline solar cells. Suns-VOC measurement clearly indicate that the recombination current densities within the space charge region (J02) and rest of the solar cells (J01) together play an important role in light and elevated temperature induced degradation (LeTID) and subsequent regeneration characteristics. During the degradation phase, both J01 and J02 changed significantly for monocrystalline and multicrystalline solar cells. During regeneration, even though J01 improved for both the types of solar cells, notable reduction in J02 was observed only for monocrystalline solar cells. FF loss analysis shows that the recombination in the space charge region is majorly responsible for degradation and regeneration in FF. In contrast to most of the previous studies, we report similar reduction in external quantum efficiency (EQE) at 984 nm, 877 nm and 658 nm and propose that the formation of defects related to LeTID are not only in the deep bulk, but are distributed throughout the bulk. Absence of any improvement in EQE after prolonged exposure to light and heat suggests that defect transformation and gettering are not sufficient enough to regenerate JSC in multicrystalline solar cells. EQE maps at 407 nm suggest that LeTID behavior of emitter is different from that of bulk.

Double-Barrier Quantum-Well Structure: An Innovative Universal Approach for Passivation Contact for Heterojunction Solar Cells

The main drawbacks of modern solar-cell technologies are low-quality surface passivation, recombination losses, and carrier selectivity, which limit their efficiency. Therefore, this study proposes an innovative universal approach for a double-barrier two-dimensional (2D) quantum well (QW) passivation structure for solar cells. To this end, c-Si solar cells were examined as model cells. Preliminary investigations (e.g., contact resistance, passivation, and recombination current density) were conducted with a stack of SiOx/nc-Si/SiOx QW on n-type surfaces, and excellent results were obtained with a 30 nm-thick nc-SiOx(n) carrier-selective layer. Furthermore, the effects of different QW thicknesses and doping doses on the surface passivation of such contacts were studied, and the best results were achieved for a 5 nm QW. These QWs also exhibited a low degree of dopant diffusion, which was suppressed by the double SiOx layer. Furthermore, the 2D QW passivation structure with carrier-selective layers, which was denoted as a heterojunction with quantum well (HQW) solar cell, exhibited an excellent passivation improvement and had a lifetime (τeff) of 2746 μs and an implied open-circuit voltage (iVoc) of 736 mV for a 5 nm 2D QW structure. Moreover, a fabricated 5 nm 2D QW-based silicon heterojunction (SHJ) solar cell exhibited an open-circuit voltage (Voc) of 732.5 mV, a short-circuit current density (Jsc) of 39.5 mA/cm2, a fill factor (FF) of 77.95%, and an efficiency (Eff) of 22.55%. To validate these findings, theoretical calculations were performed using the experimental results, which confirmed the resonance tunneling of charge carriers across the 5 nm HWQ structure.

Surface modifications by wet oxidation method removing getter layer in crystalline silicon cells.

Reducing the impurity atom content in crystalline silicon (c-Si) can effectively reduce the recombination current density (J 0) and improve the photoelectric conversion efficiency (PCE) of solar cells. Phosphorus diffusion gettering (PDG) has been proven to be an effective method to remove impurity atoms from c-Si. However, the research studies show that the traditional tube thermal diffusion method will cause a large number of dislocations on the silicon surface during the oxidation process, reducing the effectiveness of gettering. In this paper, the wet oxidation method is systematically used to remove phosphorus-rich layers (PRL) and modify the surface. The gettering effectiveness is measured by the minority carrier lifetime (τ eff) and bulk carrier lifetime (τ bulk) of silicon wafers. The results show that wet oxidation can reduce J 0 by 27.0% and increase τ eff by 26.3%. For the bulk region, the average τ bulk can be increased by more than 6-14%. In addition, with the final PCE comparison, the efficiency of the wet oxidation cell will be improved by 0.12%. These works indicate that the wet oxidation method can significantly improve the gettering effectiveness and the PCE of c-Si solar cell fabrication.

A novel passivating contact approach for enhanced performance of crystalline silicon solar cells

Passivated contacts based on ultrathin silicon oxide (SiOx) layers and phosphorus-doped nanocrystalline silicon oxide (nc-SiOx(n)) layers have been examined for their application in tunnel oxide-passivated contact (TOPCon) solar cells. Passivated contact nc-SiOx(n)/SiOx, is accomplished by implementing a thermally grown SiOx tunnel layer and a plasma-enhanced chemical vapor deposited (PECVD)-grown nc-SiOx(n) layer, which are subsequently transformed into a more crystalline phase by annealing at a higher temperature. In this research, a 3.2 × 3.2 cm solar cell was fabricated, where the base material was n-type crystalline silicon (c-Si(n)), and an aluminum oxide (Al2O3) acts as a passivation layer which helps to enhanced the passivation properties and indium tin oxide (ITO) layer was used on the front side, which could serve as an anti-reflection coating (ARC), respectively. The influence of the temperature, doping level, and thickness of nc-SiOx(n) on the surface passivation of the contacts was investigated. Superior recombination current density (Jo) values of up to 2.9 fA/cm2 were assessed for the nc-SiOx(n)/SiOx contacts. TOPCon solar cells with top boron-doped emitter, Al2O3, and ITO/rear stack of nc-SiOx(n)/SiOx passivation contacts were formed and resulted in Voc = 650 mV and FF = 78%. Furthermore, we focused on ameliorating the achievements of solar cells using a transparent passivating contact-based nc-SiOx(n), as well as the passivation process and operating principle.

Full quantum simulation of Shockley–Read–Hall recombination in p-i-n and tunnel diodes

We have included Shockley–Read–Hall (SRH) generation/recombination in Non-equilibrium Green’s function (NEGF) calculations via a multiphonon relaxation model. The model has been used to study how the presence of defects affects the current–voltage characteristics of GaAs p-i-n diodes, and of an InGaAs tunnel diode. Regarding p-i-n diodes, we show that SRH generation/recombination is responsible for ideality factors approaching the theoretical value of two in the forward bias regime, while in reverse bias the recombination current density varies slowly with the applied voltage. In all the considered cases, the defects located in the center of the active region proved to be the most effective in allowing trap-assisted tunneling from the valence to the conduction band. Finally, the inclusion of SRH recombination in NEGF simulations of Esaki tunnel diodes permits to predict a realistic degradation of the peak-to-valley current ratio.

Poly-Si thickness and temperature dependent oxide disruption induced by penetration of the interfacial oxide in (p) poly-Si/SiOx passivating contacts

Passivating contacts based on polycrystalline silicon on an interfacial oxide (poly-Si/SiO x ) require a fine-tuned in-diffused dopant profile at the surface of the crystalline silicon wafer. In particular, a strong dopant in-diffusion causes excessive recombination. This study contributes to reveal the yet unclear mechanism of this degradation of passivation. Boron in-diffusion from co-sputtered (p) poly-Si layers through the interfacial oxide is investigated for several layer thicknesses and plateau temperatures during the solid phase crystallization. It is shown that for higher temperatures and unexpectedly also for thicker layers the observed recombination current density increases up to a total loss of passivation, accompanied by a physical interfacial oxide disruption, which is not observed for intrinsic reference layers. This behavior is supported by simple numerical calculations. The recombination current densities are transferred into the actual surface recombination velocity which in turn reveals an exponential increase towards higher boron concentrations at the interface between the oxide and the crystalline Si base. It is concluded that rather dopant penetration of the interfacial oxide is responsible for the degradation of passivation than the actual boron concentration at the interface itself as reported before in literature. • Co-sputtered (p) poly-Si/SiO x passivating contacts degrade towards thicker poly-Si and higher annealing temperatures. • The identified degradation mechanism is a physical disruption of the interfacial oxide. • The degradation is rather driven by boron penetration than by the actual boron concentration at the interface. • Modelling of the actual surface recombination velocity reveals an exponential relation to the interface boron concentration.

Atomic scale controlled tunnel oxide enabled by a novel industrial tube‐based PEALD technology with demonstrated commercial TOPCon cell efficiencies > 24%

AbstractIn this work, we report on a significant breakthrough in fabricating the critical tunnel oxide layer of tunnel oxide passivated contacts (TOPCon) high‐efficiency solar cells compatible with high‐volume manufacturing. We show that the tunnel oxide can be controlled at the atomic scale, enabled by an innovative tube‐type industrial plasma‐assisted atomic layer deposition (PEALD) method. In combination with an in situ doped poly‐Si (n+) layer grown by plasma‐enhanced chemical vapor deposition, a uniform, ultrathin ~1.3 nm SiOxlayer is obtained at thec‐Si/SiOx/poly‐Si (n+) interface. Extremely low recombination current densities down to 2.8 fA/cm2and an implied open‐circuit voltage (iVoc) as high as 759 mV are achieved, comparable to state‐of‐the‐art laboratory results. The developed tube‐type PEALD SiOxis applied to industrial TOPCon solar cells resulting in a solar cell efficiency and open‐circuit voltage of up to 24.2% and 710 mV, respectively. The tunnel oxide process window is about 2.4 Å, highlighting the importance of precisely controlling the tunnel oxide thickness at the atomic scale for TOPCon solar cells. The newly developed tube‐type industrial PEALD SiOxmethod opens up a promising new route toward mass production of high‐efficiency industrial TOPCon solar cells. Furthermore, the developed tube‐type PEALD method can easily be integrated with the industrial tube‐type plasma‐enhanced chemical vapor deposition (PECVD) method, thus enabling the deposition of all thin film layers in TOPCon solar cells in one integrated PEALD/PECVD system. This significantly simplifies manufacturing complexity and fosters the commercialization of next‐generation high‐efficiency industrial TOPCon solar cells.

Surface passivation in c-Si solar cells via a double-barrier quantum-well structure for ameliorated performance

Modern solar cell technology suffers low surface passivation, high recombination losses at the interface, and dopant diffusion losses that limit solar cell’s efficiency. Therefore, a double-barrier quantum-well (DBQW) structure-based surface passivation contact is introduced here to resolve these shortcomings. In this regard, DBQWs of different thicknesses with stacks of SiOx/ nc-SiOx (3, 5, 8, and 10 nm)/SiOx layers were explored as surface passivation layers and dopant diffusion barriers. Multiple characterizations were utilized to examine DBQW thickness-dependent properties, such as contact resistance, passivation, and recombination current density; the best result was for the 5-nm-thickness QW passivation layer. To justify the obtained result, theoretical calculations were carried out based on the experimental results, which suggested the resonance tunneling of charge carriers across the 5 nm DBQW structure. Furthermore, SIMS was explored to examine the diffusion barrier property of these QWs, which revealed that dopant diffusion was suppressed by the QW with the double SiOx layer. Finally, the nc-SiOx(n) /5-nm QW/c-Si surface passivation structure showed substantial enhancement in a lifetime (τeff) of 3560 μs, an implied open-circuit voltage (iVoc) of 735 mV, and reduced recombination current density (Jo) = 1.5 fA/cm2.

Fill Factor Losses and Deviations from the Superposition Principle in Lead Halide Perovskite Solar Cells

The enhancement of the fill factor in the current generation of perovskite solar cells is the key for further efficiency improvement. Thus, methods to quantify the fill factor losses are urgently needed. Two methods are presented to quantify losses due to the finite resistance of the semiconducting layers of the solar cell as well as its contacts. The first method is based on the comparison between the voltage in the dark and under illumination analyzed at equal recombination current density and results in a voltage‐dependent series resistance. Furthermore, the method reveals the existence of a strong photoshunt under illumination. The second method is based on measuring the photoluminescence of perovskite solar cells as a function of applied voltage. Thereby, the recombination current is determined as a function of voltage from short circuit to open circuit, and the presence of the photoshunt is explained with a high resistance of the electron and/or hole transport layers combined with field screening in the absorber.

Outstanding Surface Passivation for Highly Efficient Silicon Solar Cells Enabled by Innovative AlyTiOx/TiOx Electron‐Selective Contact Stack

Passivating contacts based on transition metal oxides (TMOs) have the potential to overcome existing performance limitations in high‐efficiency crystalline silicon (c‐Si) solar cells, which is a significant driver for continuing cost/Watt reductions of photovoltaic electricity. Herein, innovative stacks of Al‐alloyed TiO x (Al y TiO x ) and pure TiO x as transparent electron‐selective passivating contacts for n‐type c‐Si surfaces are explored. An optimized stack of 2 nm Al y TiO x and 2 nm TiO x is shown to provide both record‐quality surface passivation and excellent electrical contact, with a surface recombination current density prefactor J 0 of 2.4 fA cm−2 and a specific contact resistivity ρ c of 15.2 mΩ cm2. The performance of this innovative stack significantly exceeds previously reported values for pure or doped TiO x single layers, SiO x /TiO x stacks, a‐Si:H/TiO x stacks, and other transparent contact technologies. Furthermore, an excellent efficiency of 21.9% is attained by incorporating the optimized stack as a full‐area rear contact in an n‐type c‐Si solar cell. The findings set a new benchmark for the passivation performance of metal oxide‐based passivating contacts, bringing it to a level on par with state‐of‐the‐art SiO x /poly‐Si contacts while greatly improving optical transparency.

Enhanced energy conversion performance of silicon solar cells by quantum-confinement effect of polysilicon oxide

We propose a highly transparent polysilicon oxide (poly-SiOx)/crystalline silicon (c-Si) front passivation contact (poly-SiOx/c-Si) to overcome the parasitic current drawback and enhance the stability of silicon heterojunction (SHJ) solar cells. Poly-SiOx has a mixed-phase crystalline structure with large crystalline grains embedded in a wide-gap amorphous silicon oxide (a-SiOx) matrix, resulting in a quantum confinement effect. While the large crystalline phase facilitates dopant activation toward high conductivity (elevated Fermi level), resulting in substantial band bending at the c-Si/poly-SiOx interface for additional field-effect passivation, the a-SiOx matrix allows additional chemical surface passivation. Thus, passivation quality with an implied open-circuit voltage of 732 mV and a recombination current density of 4.3 fA/cm2 was achieved. Owing to the interaction between the quantum confinement effect and the wide-gap a-SiOx phase, the mixed-phase structure had a wide bandgap (1.98 eV), significantly increasing the absorption of the device in the short-wavelength region (≤500 nm). A hybrid rear-emitter SHJ solar cell using poly-SiOx/c-Si achieved an efficiency of 23.95% with Voc = 723 mV, a short-circuit current density of 40.9 mA/cm2, and a fill factor of 81%.

Sputtered Phosphorus‐Doped poly‐Si on Oxide Contacts for Screen‐Printed Si Solar Cells

The impact of the phosphorus doping density in direct current‐sputtered polysilicon layers on surface passivation and contact resistance by fabricating polysilicon on oxide (POLO) contacts is studied, when applying doping densities ranging from 3 × 1019 to 4 × 1020 cm−3. Hydrogenation is performed either via a hydrogen‐releasing AlO x layer and postdeposition anneals in forming gas using a tube furnace at 400 °C, or by rapid firing of an AlO x /SiN y stack in a conveyor belt furnace at 810 °C. The study shows that the forming gas anneal of the weakly in situ phosphorus‐doped poly‐Si layers with AlO x enables a passivation quality with an implied open‐circuit voltage of up to 734 mV and a recombination current density down to 1.8 fA cm− 2. For fast firing, a high phosphorus concentration of 4 × 1020 cm−3 is required for comparably high passivation quality with a recombination current density down to 1.3 fA cm− 2. A p‐type POLO back‐junction solar cell featuring such ex situ doped sputtered POLO contacts with a cell efficiency of 22.4% and an open‐circuit voltage of 714 mV is fabricated. To our knowledge, this is the highest open‐circuit voltage published so far with sputtered POLO contacts.

Interdigitated back-contacted crystalline silicon solar cells fully manufactured with atomic layer deposited selective contacts

The interdigitated back-contacted (IBC) solar cell concept has been extensively studied for single-junction cells and more recently as a good choice for three-terminal tandem devices. In this work, carrier-selective contacts based on transition metal oxides deposited by atomic layer deposition (ALD) technique are applied to IBC c-Si(n) devices. In the first part of the study, we develop a hole-selective contact based on thin ALD vanadium oxide (V2O5) layers without using an amorphous silicon interlayer. The ALD process has been optimised, i.e. number of ALD cycles and deposition temperature, as a trade-off between surface passivation and contact resistivity. Noticeable surface passivation with recombination current densities around 100 fA/cm2, as well as reasonable contact resistivity values below 250 mΩcm2 are reached using 200 ALD V2O5 cycles deposited at a deposition temperature of 125 °C (∼10 nm layer thickness). The optimised ALD V2O5-based contact is combined with both an ALD TiO2-based electron-selective contact and an excellent surface passivation in non-contacted regions provided by ALD Al2O3 films, to form a fully ALD IBC c-Si(n) solar cell scheme. Fabricated devices yield photovoltaic efficiencies and pseudo efficiencies, i.e. calculated without series resistance losses, of 18.6% and 21.1% respectively (3 cm × 3 cm device area). These results reveal the potential of the ALD technique to deposit transition metal oxide (TMO) films as selective contacts on high efficiency devices, paving the way of using low thermal-budget, low cost and highly scalable processes for a highly demanding IBC solar cell architecture in the photovoltaic industry.

Industrial metallization of fired passivating contacts for n-type tunnel oxide passivated contact (n-TOPCon) solar cells

Poly-Si/SiO x passivating contacts enable the manufacturing of highly-efficient Si solar cells, but their fabrication commonly relies on an extra high-temperature process such as dopant diffusion or thermal annealing for achieving excellent passivation and contacting properties. This extra process is eliminated in the fired passivating contact (FPC) approach used for simplified fabrication of poly-Si/SiO x passivating contacts. Instead, FPCs rely on the thermal budget of the fast/short and high-temperature firing process used for metallization of solar cells to achieve similar final properties. Despite this, compatibility of FPCs with industrially viable metallization techniques has not been demonstrated yet, which is studied in this work for fire-through Ag screen-printing and Ni/Ag plating. With screen-printing, low recombination current density ( J 0 ) down to 4.9 fA/cm 2 , low contact resistivity between the Ag contacts and the FPC ( ρ c,m ) down to 7.2 mΩ⋅cm 2 , and Ohmic transport through the FPC including the SiO x film were achieved using wet-chemically grown SiO x . Nevertheless, J 0 of metallized regions ( J 0,m ) exceeded 1000 fA/cm 2 . Reducing J 0,m was attempted by mitigating the blistering observed in FPCs, but J 0,m remained high. With Ni/Ag plating, excellent surface passivation with J 0 down to 2.7 fA/cm 2 and very low J 0,m < 50 fA/cm 2 were achieved, but no Ohmic contacts could be obtained. Integration of screen-printed FPCs in large-area n-TOPCon solar cells was also demonstrated, yielding average efficiencies of 18.4%, limited mainly by the high J 0,m and series resistance of the FPCs. The results presented reveal the challenges for the industrialization of FPCs and provide valuable insights for tackling these. • Fired passivating contacts (FPCs) developed relying only on the thermal budget of firing and not on conventional annealing. • Compatibility of FPCs with fire-through Ag screen-printing and Ni/Ag plating tested. • Screen-printing: J 0,pass ≈ 5 fA/cm 2 & ρ c < 10 mΩ∙cm 2 achieved, but J 0,metal was high. • Plating: J 0,pass < 3 fA/cm 2 & J 0,metal < 50 fA/cm 2 achieved, but contacts were non-Ohmic. • Integration of FPCs in screen-printed large-area n-TOPCon cells led to 18.4% efficiency.

Emitter formation with boron diffusion from PECVD deposited boron-doped silicon oxide for high-efficiency TOPCon solar cells

We present a systematic study of emitter formation with dopant diffusion from boron (B)-doped hydrogenated silicon oxide (a-SiOx:H) deposited on textured n-type monocrystalline silicon (n-c-Si) wafers using a 13.56 MHz plasma-enhanced chemical vapor deposition (PECVD) system. The B atoms in the a-SiOx:H are activated and diffused into the n-c-Si wafer during a high-temperature annealing to form a p/n junction for solar cell application. Afterward, the B-doped SiOx layer is removed by hydrofluoric acid selective etching to obtain a clean surface for the deposition of AlOx passivation and SiNx antireflection layers. With the optimization of the PECVD deposition and the following annealing/etching processes, the B diffused region with a sheet resistance of 60–100 Ω/sq and a junction depth of 1.2–1.5 μm is obtained. A champion implied open-circuit voltage (iVoc) of 705 mV and a single-side saturated recombination current density (J0,s) of 17.6 fA/cm2 are obtained from a double-sided B diffused sample after the passivation with an atomic-layer-deposition (ALD) AlOx. In addition, the contact resistivity (ρc) at the metal/emitter interface is lower than 5 mΩcm2, where the metal contact is a Ti/Pd/Ag tri-layer structure. All of the material properties meet the requirements of high-efficiency solar cell. With the optimized emitter in the front, we made a SiOx and heavily phosphorus-doped polycrystalline silicon carbide (n-poly-SiCx) stack on the rear surface to form tunnel oxide passivated contact (TOPCon) solar cells. The results show that the iVoc of semi-finished TOPCon solar cell before metallization is more than 725 mV. Finally, a TOPCon solar cell with an efficiency of 24.24% is obtained, which is comparable with the TOPCon solar cells with the industrial thermally diffused emitter.

Small signal analysis of the modulation bandwidth of light-emitting diodes for visible light communication

We perform a theoretical investigation of the small-signal modulation characteristics of light-emitting diodes (LEDs) for visible light communication (VLC) applications. A comprehensive model for the small-signal frequency bandwidth is developed using a carrier rate equation with the ABC recombination model. Using the obtained general form of the 3-dB bandwidth (f3dB), we analyze the dependence of the bandwidth on various parameters of the LEDs. The internal quantum efficiency (IQE) is found to significantly influence the modulation bandwidth of LEDs. At a high current density, f3dB is approximately inversely proportional to IQE, suggesting the importance of a trade-off between high IQE and fast modulation speed. In addition, we analyze and discuss the effects of the radiative recombination coefficient, current density, and quantum-well thickness on f3dB, comparing the modeling results with previous experimental data. The presented model of the modulation bandwidth can be advantageous in understanding the modulation characteristics of LEDs for high-speed VLC.

Influence of Silicon Substrate Surface Finish on the Screen‐Printed Silver Metallization of Polysilicon‐Based Passivating Contacts

Passivated contact based on a thin interfacial oxide and a highly doped polysilicon layer has emerged as the next evolutionary step to increase the efficiencies of industrial silicon solar cells. To take maximum advantage from this layer stack, it is vital to limit the losses at the metal polysilicon interface, which can be quantified as metal polysilicon recombination current density (J0met) and contact resistivity. In cell concepts, wherein a large variety of silicon substrate surface finish can be obtained, it is essential to know how the surface finish affects theJ0metand contact resistivity. Herein, commercially available fire through silver paste and the metal‐polysilicon recombination current densities and contact resistivity are used for three different silicon substrate surface finishes, namely: planar or saw damage etched (SDE), chemically polished in acidic solution and alkaline pyramidal textured. Contact resistivity values below 3 mΩ cm2withJ0metin order of the recombination current density of the doped region (J0pass) are obtained for samples with planar surface for both 150 and 200 nm n+polysilicon layer thicknesses. The results presented in this work show that the samples with flat substrate morphology outperform the samples with textured surfaces.

Impacts of plasmonic nanoparticles incorporation and interface energy alignment for highly efficient carbon-based perovskite solar cells

This work utilizes a realistic electro-optical coupled simulation to study the (i) impact of mesoporous TiO2 removal; (ii) the embedding of Ag@SiO2 and SiO2@Ag@SiO2 plasmonic nanoparticles; (iii) utilization of solution-processed inorganic p-type copper(I) thiocyanate (CuSCN) layer at the perovskite/carbon interface; and (iv) the increase of the work function of carbon electrodes (via incorporation of suitable additives/binders to the carbon ink) on the performance of carbon-based PSCs. Removal of mesoporous TiO2 increased the power conversion efficiency (PCE) of the device from 14.83 to 16.50% due to the increase in exciton generation rate and charge carriers’ mobility in the vicinity of the perovskite-compact TiO2 interface. Subsequently, variable mass ratios of Ag@SiO2 and SiO2@Ag@SiO2 plasmonic nanoparticles are embedded in the vicinity of the perovskite-compact TiO2 interface. In the optimum cases, the PCE of the devices increased to 19.72% and 18.92%, respectively, due to light trapping, scattering, and strong plasmonic fields produced by the plasmonic nanoparticles. Furthermore, adding the CuSCN layer remarkably increased the PCE of the device with a 0.93% mass ratio of Ag@SiO2 nanoparticles from 19.72 to 26.58% by a significant improvement of Voc and FF, due to the proper interfacial energy band alignment and the reduction of the recombination current density. Similar results were obtained by increasing the carbon work function, and the cell PCE was enhanced up to 26% in the optimal scenario. Our results pave the way to achieve high efficiencies in remarkably stable printable carbon-based PSCs.

Large-area bifacial n-TOPCon solar cells with in situ phosphorus-doped LPCVD poly-Si passivating contacts

The potential of passivating contacts incorporating in situ phosphorus (P)-doped polycrystalline silicon (poly-Si) films grown by low pressure chemical vapor deposition (LPCVD) is demonstrated in this work by integrating these layers at the rear side of large-area (241.3 cm 2 ) bifacial n-type Tunnel Oxide Passivated Contact (n-TOPCon) solar cells with diffused front emitter and screen-printed contacts. In situ doped poly-Si films are studied as their use could simplify the production of industrial n-TOPCon solar cells compared to the common approach relying on ex situ doping of intrinsic LPCVD poly-Si films. The developed poly-Si passivating contacts exhibited excellent characteristics with low recombination current densities in passivated and screen-printing metallized regions down to 2.3 fA/cm 2 and 65.8 fA/cm 2 , respectively, and a low contact resistivity of 2.0 mΩ⋅cm 2 . For reaching the best passivating contact characteristics and high solar cell efficiencies, a poly-Si film thickness of 150–200 nm was found to be optimal while a polished rear surface morphology was found to be beneficial. The best solar cell reached a certified power conversion efficiency of 23.01% along with a high open circuit voltage of 691.7 mV, enabled by the passivating contacts with the in situ doped poly-Si films. 1-cell glass-glass laminates were also fabricated with the developed solar cells, which showed no loss in their power output both upon 400 thermal cycles and after 1000 h of damp heat testing. Lastly, a roadmap is presented, indicating strategies to achieve efficiencies up to 25.5% with n-TOPCon solar cells incorporating the in situ P-doped LPCVD poly-Si films. • In situ P-doped LPCVD poly-Si passivating contacts integrated in n-TOPCon solar cells. • 241.3 cm 2 -large bifacial n-TOPCon devices with 23.01% certified efficiency demonstrated. • Using ≥ 150 nm of poly-Si and polished rear side improves the solar cell efficiency. • 1-cell glass-glass laminates of the devices pass damp heat and thermal cycling tests. • Roadmap to 25.5% efficiency presented.