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Summary Cost-effective photovoltaics (PVs) require a high energy yield with a long system lifetime. However, both are adversely affected by temperature. Here, we assess the economic impact of thermal effects on PV systems by establishing a temperature-dependent levelized cost of energy (LCOE) model. Using this model, we introduce an equivalent ratio γ (with the unit of absolute efficiency %/K) as a new metric that quantitatively translates the LCOE gain obtained by reducing the module temperature ( T m o d ) to an equivalent absolute power conversion efficiency increase. The substantial value of γ motivates us to investigate the root causes of heating in solar cells and modules, with a focus on crystalline-Si (c-Si) PVs, given its market dominance. To link the heat analysis with T m o d , we establish and validate an opto-electronically coupled thermal model to predict T m o d . This modeling approach enables the quantification of possible ways to mitigate undesired heating effects.

Perovskite/silicon tandem solar cells promise power conversion efficiencies beyond the Shockley–Queisser limit of single-junction devices; however, their actual outdoor performance is yet to be investigated. Here we fabricate 25% efficient two-terminal monolithic perovskite/silicon tandem solar cells and test them outdoors in a hot and sunny climate. We find that the temperature dependence of both the silicon and perovskite bandgaps—which follow opposing trends—shifts the devices away from current matching for two-terminal tandems that are optimized at standard test conditions. Consequently, we argue that the optimal perovskite bandgap energy at standard test conditions is

Summary Silicon heterojunction (SHJ) solar cells employ nanometer-thin stacks of intrinsic and doped hydrogenated amorphous silicon (a-Si:H) films as carrier-selective contacts. To achieve excellent carrier selectivity, the a-Si:H must be carefully optimized to guarantee an atomically sharp a-Si:H/c-Si interface. In this work, by combining experiments with molecular dynamics and ab initio calculations, we unveil that H atoms bonded to internal-void surfaces in a-Si:H broaden its optical band gap via a filamentary effect near the valence-band maximum. The photovoltaic performance of rear-emitter SHJ solar cells can be significantly improved by tailoring the Si−H bonding state in the front a-Si:H passivation layer, resulting in a power conversion efficiency (PCE) of 23.4% on a 6-in cell. By implementing double antireflection coatings (ARCs) of SiNx and SiOx, the PCE is further improved to 23.9%. More importantly, the ARC devices show prominently improved damp-heat stability without encapsulation in 1,000-h aging at 85°C, 85% relative humidity.

Polysilicon passivating contacts, consisting of a stack of tunnel-oxide and doped polysilicon layers, can simultaneously provide excellent surface passivation and low contact resistivity for silico...

Summary High-performance passivating contact is a prerequisite for high-efficiency crystalline silicon (c-Si) solar cells. In this work, an electron-conductive, hole-blocking contact based on titanium nitride (TiN) deposited by reactive magnetron sputtering is presented. Quasi-metallic TiN combined with an ultrathin SiO2 passivation layer (SiO2/TiN) is demonstrated to be an effective electron-selective contact on c-Si, featuring a low-contact resistivity of 16.4 mΩ.cm2 and a tolerable recombination current parameter of ∼500 fA/cm2. By implementing the dual-function SiO2/TiN contact, which acts simultaneously as a surface passivating layer and metal electrode, an efficiency of 20% is achieved by an n-type c-Si solar cell with a simple structure. This work not only demonstrates a way to develop efficient n-type c-Si solar cells with dual-function metal nitride contacts at a low cost but also expands the pool of available carrier transport materials, from metal oxides to metal nitrides, for photovoltaic devices.

This paper outlines the development of fully screen-printed, uniformly diffused, bifacial, n-type silicon solar cells produced using a lean processing sequence and industry-standard equipment. An average batch efficiency of 21.4% was measured at standard test conditions for an optimised bifacial cell batch (i.e. illumination on the front surface only). The results of open circuit voltage (VOC) and fill factor (FF) loss analyses are presented for select batches. By targeting reductions in the largest recombination components, optimised batch VOC was increased by 15 mV compared to the baseline case. The two largest recombination components limiting VOC in optimised devices are front contact recombination and passivated rear surface recombination. The largest FF loss components for optimised devices are the emitter sheet resistance and front contact resistance.

Bifacial monolithic perovskite/silicon tandem solar cells exploit albedo—the diffuse reflected light from the environment—to increase their performance above that of monofacial perovskite/silicon tandems. Here we report bifacial tandems with certified power conversion efficiencies >25% under monofacial AM1.5G 1 sun illumination that reach power-generation densities as high as ~26 mW cm–2 under outdoor testing. We investigated the perovskite bandgap required to attain optimized current matching under a variety of realistic illumination and albedo conditions. We then compared the properties of these bifacial tandems exposed to different albedos and provide energy yield calculations for two locations with different environmental conditions. Finally, we present a comparison of outdoor test fields of monofacial and bifacial perovskite/silicon tandems to demonstrate the added value of tandem bifaciality for locations with albedos of practical relevance. Bifacial solar cells can outperform monofacial cells by exploiting sunlight reflected off the ground surface. De Bastiani et al. show that bifacial perovskite/silicon tandem with an optimized bandgap can deliver a power density of 26 mW cm–2 and compare its performance to monofacial cells under outdoor conditions.

Parasitic absorption in transparent electrodes is one of the main roadblocks to enabling power conversion efficiencies (PCEs) for perovskite‐based tandem solar cells beyond 30%. To reduce such losses and maximize light coupling, the broadband transparency of such electrodes should be improved, especially at the front of the device. Here, the excellent properties of Zr‐doped indium oxide (IZRO) transparent electrodes for such applications, with improved near‐infrared (NIR) response, compared to conventional tin‐doped indium oxide (ITO) electrodes, are shown. Optimized IZRO films feature a very high electron mobility (up to ≈77 cm2 V−1 s−1), enabling highly infrared transparent films with a very low sheet resistance (≈18 Ω □−1 for annealed 100 nm films). For devices, this translates in a parasitic absorption of only ≈5% for IZRO within the solar spectrum (250–2500 nm range), to be compared with ≈10% for commercial ITO. Fundamentally, it is found that the high conductivity of annealed IZRO films is directly linked to promoted crystallinity of the indium oxide (In2O3) films due to Zr‐doping. Overall, on a four‐terminal perovskite/silicon tandem device level, an absolute 3.5 mA cm−2 short‐circuit current improvement in silicon bottom cells is obtained by replacing commercial ITO electrodes with IZRO, resulting in improving the PCE from 23.3% to 26.2%.

We present an electron-conductive, hole-blocking contact for silicon solar cell in this work. Quasi-metallic titanium nitride (TiN), deposited by reactive magnetron sputtering, is proven to be an effective electron-selective contact for silicon solar cell, simultaneously achieving a low contact resistivity (ρ c ) of ~ 16 mΩ∙cm2 and a tolerable contact recombination parameter (J 0c ) of ~ 500 fA/cm2. By the implementation of the dual-function SiO 2 /TiN contact, which acts simultaneously as efficient surface passivating and metal electrode, a power conversion efficiency of 20% is achieved on an n-type silicon solar cell with a simple structure. This work demonstrates a way to develop efficient n-type Si solar cells with dual-function metal nitride contacts at a low cost.

We report a novel flexible solar tracking system based on a photothermal-thermomechanical (PT-TM) actuator comprised of Ti3C2Tx MXene and polyvinylidene fluoride (PVDF) bilayer. The actuation function of the proposed device originates from photothermal and surface plasmon-assisted effects in MXenes, coupled with thermomechanical deformation of in-plane aligned PVDF polymer. Two types of solar tracking modes are evaluated based on the experimental deformation behavior of the PT-TM actuator. We find that the uniaxial East-West solar tracking option increases the overall energy intensity reaching the solar module by over 30%, in comparison with the optimized tilting-controlled mode. We also demonstrate the thermally driven self-oscillation of the MXene-PVDF device, which may have promising potential for optically and thermally driven soft robotics. The PT-TM actuator devices display robust mechanical strength and durability, with no noticeable degradation in their performance after more than 1000 cycles.

The main challenge for interdigitated back-contact (IBC) solar cells is to reduce the fabrication complexity, which consists of multiple high-temperature processing and patterning steps. Patterned ion implantation has been proposed to simplify the manufacture of IBC solar cells, and the annealing of boron and phosphorus implanted areas is still a problem for the application. In this study, a new method consisting of laser annealing and a subsequent low-temperature oxidation (LA&OX) has been developed to co-anneal boron implanted p + and phosphorus implanted n + regions by a single step. We found that an additional laser annealing before oxidation could improve the electrical properties of boron-implanted p + regions effectively; however, it has almost no effect on the phosphorus-implanted n + regions. An industrially feasible IBC solar cell fabrication technology has been proposed based on the patterned ion implantation and LA&OX processing. The main fabrication steps of the IBC solar cell could be reduced to ten steps, and only one high-temperature oxidation step is required. As-designed IBC cell shows a potential efficiency higher than 23% according to simulations with the experimental parameters.

Laser doping of semiconductors has been the subject of intense research over the past decades. Previous work indicates that the use of SiO2/SiNx stacks instead of a single dielectric film as the anti-reflection coating and passivation layer results in laser doped lines with superior properties. In this paper, the impact of the SiNx layer thickness in the SiO2/SiNx stacks on the properties of laser doped lines is investigated through resistance measurements of the laser doped line and the silicon-metal contact and the doping profile near the edge of the dielectric window, the latter being an important factor in determining the likelihood of high recombination or even shunting from the subsequent metallization process. Fundamentally, a problem of exposed and undoped silicon near the dielectric window is identified for most of the investigated parameter range. However, optimization of the laser parameters and dielectric film conditions is shown to be capable of preventing or at least minimizing this problem. The results indicate that for the used laser system, samples with thick dielectric stack processed using a low pulse energy and pulse distance yield the most favorable properties, such as low line resistance and low contact resistivity. Under these conditions, the laser doped regions laterally extend underneath the dielectric films, thus reducing the likelihood of high surface recombination.

Laser doping has been the subject of intense research over the past decade, due to its potential to enable high-efficiency, low-cost silicon solar cell fabrication. Information about the doping profile that is created by the process is critical for process optimization but is generally difficult to obtain. We apply the technique of secondary electron image (SEI) contrast to the characterization of the cross sections of laser-doped lines. We demonstrate that this technique can be used for a large range of different dopant sources and different laser doping methods and that good dopant contrast can be obtained under a relatively wide range of microscope parameters. Comparison of dopant contrast and doping density profiles shows that the substrate doping is an important parameter that can significantly influence the dopant contrast, particularly at low (~1018 cm-3) and high (~10 20 cm-3 ) dopant densities. When suitable calibration samples are used, the technique can be employed to obtain quantitative dopant density images for p-type laser-doped regions, albeit currently over a limited range of dopant densities and with relatively large error. Furthermore, the technique can be used to evaluate the risk of metallization shunts near the edges of dielectric film windows that are opened by the laser.

In this work, n-type silicon solar cells with local back surface field (LBSF) formed by Laser Chemical Processing (LCP) is presented. The effect of rear passivation layer and LBSF pitch on the efficiency is investigated. The SiO2/a-Si: H passivated contact is implemented into the n-type solar cells with LCP-LBSF. With the optimal pitch, an average efficiency of 20.4% and 19.8% is achieved on the LCP processed n-type solar cells with SiO2/SiNx stack and single SiNx rear passivation, respectively. Those cells' efficiency is mainly limited by the high surface recombination at the LCP doped regions. With the implementation of the SiO2/a-Si:H passivated contact to the LCP regions, an absolute efficiency gain of up to 1.5% is achieved for the n-type solar cells with SiNx rear passivation. The results show the potential to fabricate high efficiency n-type solar cells with simplified processing by using LCP and the passivated contact concept.

Ion implantation and laser processing technologies are very attractive for the fabrication of industrially feasible interdigitated back-contact (IBC) solar cells. In this work, p + emitters were fabricated by boron implantation and laser annealing, and the electrical properties of emitters were investigated. An emitter sheet resistance ( R sh ) in the range of 30-200 Ω/□ could be achieved by varying the implanted dose. The saturation current density ( J oe ) of the passivated p + emitter with R sh of ∼125 Ω/□ reached 95 fA/cm 2 , and the contact resistivity was determined to be as low as 5×10 -6 Ω·cm 2 . Such localized p + emitters can be applied to n-type IBC solar cells, which could avoid the high temperature thermal annealing step and related problems.

The authors acknowledge financial support from the Australian Solar Institute (ASI)/Australian Renewable Energy Agency (ARENA) under the ANU PV Core project, Postdoctoral Fellowship and Australia-Germany Collaborative Solar Research and Development projects. The authors also acknowledge support from the Australian Government’s NCRIS/EIF funding programs for access to Heavy Ion Accelerator Facilities at the Australian National University.

Laser doping of crystalline silicon has been the subject of intense research over the past decade, due to its potential to enable the fabrication of high efficiency and low-cost crystalline silicon solar cells. Information regarding the doping profile created by the process is critical for process optimisation, however is generally difficult to obtain. In this paper, a relatively new technique for characterising laser doping cross-sections — Secondary Electron Microscopy Dopant Contrast Image (SEMDCI) — is compared with the widely used Electron Beam Induced Current (EBIC) method. A good agreement between the two techniques regarding the p-n junction profile is demonstrated. The differences between the methods are attributed to the difference of the sensitivity. The comparison demonstrates the reliability and usefulness of the SEMDCI as a characterisation method for laser doping, which shows both the p-n junction outline and dopant distribution within the doped regions. The differences between the methods and the challenges associated with the application of the SEMDCI method are also discussed.

In this paper, the impact of the N2 anneal on laser processed silicon was investigated using photoluminescence (PL) imaging through comparing the PL signal of laser processed samples before and after N2 anneal. The samples capped with different dielectrics or without any dielectric (bare surface) prior to the laser processing were used, enabling the evaluation of the influence of the N2 anneal on the defects caused both by laser thermal effect and by the existence of dielectrics. Generally, it was found that N2 anneal is an effective way to reduce both the laser and dielectric induced defects.