In the paper [1], the reported values of the oxygen to total flow ratio, defined as r(O2) in %, should be multiplied by a factor of 3 ± 0.1, which corresponds to the correct calibration factor for the mass flow controllers. This correction should be applied consistently throughout the paper where the r(O2) (%) is mentioned. It is important to note that this correction does not change the conclusion of the article, and all the results presented remains valid.

Silicon heterojunction (SHJ) solar cells have reached record efficiency, particularly in all-back contacted architectures. Despite this, two-side contacted SHJ cells still suffer from parasitic absorption and series resistance losses in the amorphous silicon contacts. An alternative to the doped amorphous silicon layer is microcrystalline silicon, which exhibits improved transparency and charge transport, while maintaining the superior passivation quality of all-silicon contact stacks. However, depositing thin, highly crystalline films has remained a challenge until recently. In this work, we use deposition temperatures <200 degrees C to improve the performance of p-type mu c-Si:H contact layers. With these layers, we demonstrate J(SC) gains of 1 mA/cm(2), while reducing series resistance below 1 Omega cm(2), leading to screen printed 4 cm(2) cells with certified eta = 23.45%. Using a suite of device and material characterization techniques, we show that reduced deposition temperature leads to an increase in crystalline volume fraction from 35% to 55% for p-type films, which mitigates parasitic absorption in the front contact and facilitates hole extraction. These improvements are explained as resulting from higher transparency in the p-type layer accompanied by higher band bending in the c-Si wafer. These findings provide a method to improve SKI solar cells performance, while offering insight into the importance of hand bending considerations when optimizing heterojunction designs.

We report independently confirmed 22.15% and record 22.58% power conversion efficiencies for thin (130–140 μm) p-type and n-type monolike Si solar cells, respectively. We comparatively assessed advanced n-type and p-type monolike silicon wafers for potential use in low-cost, high-efficiency solar cell applications by using phosphorus diffusion gettering for material-quality improvement and silicon heterojunction solar cell fabrication for assessment of performance in high-efficiency photovoltaic device architecture. We show that gettering improves material quality and device properties significantly, depending on the type of doping (n-type or p-type), wafer position in the ingot, drive-in temperature, and cooling profile. Owing to the high open circuit voltage (725 mV), the record n-type solar cell also represents the highest reported solar cell efficiency for cast silicon to date.

Presents corrections to the paper, “Highly conductive and broadband transparent Zr-doped In2O3 as front electrode for solar cells,” (Morales-Masis, M. et al), IEEE J. Photovol., vol. 8, no. 5, pp. 1202–1207, Sep. 2018.

We discuss here optical losses in silicon heterojunction solar cells and strategies to minimize them. Optical losses originate from most non-crystalline-silicon layers involved in the solar cell. A breakdown for typical values is shown evidencing that suppressing absorption from the front amorphous silicon layers gives the largest gain. Other losses are interdependent, and reducing absorption from one layer in the infrared part of the spectrum boosts absorption from the other layer. The use of nanocrystalline silicon layers in lieu of amorphous silicon enables a reduction of the absorption at a given thickness but thicker layers are seen to be necessary, reducing the eventual optical gain in optimized devices. For the front transparent conductive oxide (TCO), infrared light saved from absorption in the front TCO will be shared between absorption in the c-Si wafer and in the rear electrode, and a share will also be outcoupled from the device through reflection (and transmission in the case of bifacial devices). The cell architecture will therefore dictate how much of the current saved from parasitic absorption in the front TCO will eventually benefit to the device. Using a thin ITO combined with silicon oxide is a route to provide similar electrical performances with reduced indium use and a slight cell-efficiency boost. Switching to a high-mobility Zr-doped indium oxide layer enables to use as thin as 35-nm-thick layers with still low series resistance, which outperforms optically in a cell configuration but yields similar results in a module configuration.

A monolithic two-terminal perovskite/silicon tandem solar cell based on an industrial, high-temperature tolerant p-type crystalline silicon bottom cell with a steady-state power conversion efficiency of 25.1% is demonstrated.

Tandem devices combining perovskite and silicon solar cells are promising candidates to achieve power conversion efficiencies above 30% at reasonable costs. State-of-the-art monolithic two-terminal perovskite/silicon tandem devices have so far featured silicon bottom cells that are polished on their front side to be compatible with the perovskite fabrication process. This concession leads to higher potential production costs, higher reflection losses and non-ideal light trapping. To tackle this issue, we developed a top cell deposition process that achieves the conformal growth of multiple compounds with controlled optoelectronic properties directly on the micrometre-sized pyramids of textured monocrystalline silicon. Tandem devices featuring a silicon heterojunction cell and a nanocrystalline silicon recombination junction demonstrate a certified steady-state efficiency of 25.2%. Our optical design yields a current density of 19.5 mA cm(-2) thanks to the silicon pyramidal texture and suggests a path for the realization of 30% monolithic perovskite/silicon tandem devices.

We applied hydrogen passivation, gettering and a combination of both to quasi-mono (qm) wafer material to enhance its bulk lifetime and prepared silicon heterojunction (SHJ) solar cells. We find that while our applied hydrogen passivation alone seems not to enhance lifetime, a gettering treatment increases bulk lifetime so that efficiencies up to 21.5% were achieved with a SHJ solar cell. This is close to the highest efficiency reported for such a cell. We find that the variation of the absorber thickness plays a minor role for the investigated solar cells and that similar efficiencies could have been obtained for Cz and gettered qm wafers. The latter is mainly due to the fact that the higher efficiency potential of the Cz material could not be fully exploited due to a degradation of surface passivation during the sputtering of the TCO on the cell, which could not be fully recovered in the final annealing step.

Broadband transparent and highly conducting electrodes are key to avoid parasitic absorption and electrical losses in solar cells. Here, we propose zirconium-doped indium oxide (IO:Zr) as a transparent electrode intrinsically meeting both requirements and demonstrate its application as the front electrode in silicon heterojunction (SHJ) solar cells. The exceptional properties of this material rely on the combination of high-doping and high electron mobilities, achieving with this a wide optical band gap (3.5-4 eV), low free carrier absorption, and high lateral conductivity. A single film of IO:Zr has an electron mobility of 100 cm(2)/V.s with a carrier density of 2.5-3 x 10(20) cm(-3), resulting in a sheet resistance of around 25 Omega/sq for 100-nm-thick films. Their implementation as a front electrode in SHJ solar cells results in an important gain in current density as compared to the standardly used Sn-doped indium oxide. This is due to reduced parasitic absorption in both, the UV and IR, as confirmed by external quantum efficiency measurements. SHJ devices with the optimized IO:Zr front electrode, resulting in current densities of 40 mA/cm(2), a fill factor of 80%, and a conversion efficiency of 23.4%.

Many silicon heterojunction solar cells tend to suffer modest fill factors due to high series resistance compared to homojunction or high-temperature-passivated-contact-based solar cells. Loss analysis indicates that this limitation lies in the high contact resistance between the wafer and the electrode (through the intrinsic (i) amorphous silicon (a-Si:H) passivating layer and amorphous silicon doped layers), mostly originating from the p-type contact. We implement p-type microcrystalline doped layers in heterojunction cells and demonstrate with 2-side contacted devices that a low CO2 concentration silicon oxide (SiO) plasma treatment on the a-Si: H (i) passivating layer allows to reach high crystallinity with thin layers without impeding passivation. The influence of the treatment time and CO2 concentration on lifetime and nucleation of the microcrystallites is discussed. We then show the potential of such a SiO treatment by comparing, in 2-side contacted devices, amorphous (without SiO treatment) and microcrystalline p-layer, the latter showing efficiency up to 21.5% prior to optimization.

Tandem solar cells that feature a high-bandgap perovskite cell on top of a lower bandgap silicon cell have the potential to reach efficiencies > 30%. Here, we present a versatile hybrid deposition method that yields conformal perovskite cells directly on textured silicon bottom cells, a prerequisite to achieve highest photocurrents and hence efficiencies. Furthermore, this low-temperature evaporation/spin-coating 2-step method produces high-quality perovskite materials with different bandgaps, here varied in the range of 1.5 eV to 1.8 eV. This flexibility enables the fabrication of monolithic 2-terminal perovskite/textured Si tandems that feature high photocurrents of about 19.5 mA/cm(2).

Today, solar cells are generally optimized for 25 degrees C, whereas in most climates, especially hot and sunny ones, the operating device temperature is usually much higher, e.g. in the range of 60 degrees C. We investigate the use of n-doped nanocrystalline silicon oxide layers (nc-SiOx:H(n)) as front contact stacks in silicon heterojunction solar cells and compare them with oxide-free front contacts. Whereas a short-circuit current density of 41 mAcm(-2) could be obtained due to the increased transparency of the nc-SiOx:H(n) layers, the fill-factor is drastically reduced and leads to a reduced efficiency at 25 degrees C. Albeit the FF can be partly recovered at 60 degrees C, the highest efficiencies at 60 degrees C were so far obtained for the solar cells with oxide-free front contact stacks.

Perovskite/silicon tandem solar cells are increasingly recognized as promising candidates for next-generation photovoltaics with performance beyond the single-junction limit at potentially low production costs. Current designs for monolithic tandems rely on transparent conductive oxides as an intermediate recombination layer, which lead to optical losses and reduced shunt resistance. An improved recombination junction based on nanocrystalline silicon layers to mitigate these losses is demonstrated. When employed in monolithic perovskite/silicon heterojunction tandem cells with a planar front side, this junction is found to increase the bottom cell photocurrent by more than 1 mA cm(-2). In combination with a cesium-based perovskite top cell, this leads to tandem cell power-conversion efficiencies of up to 22.7% obtained from J-V measurements and steady-state efficiencies of up to 22.0% during maximum power point tracking. Thanks to its low lateral conductivity, the nanocrystalline silicon recombination junction enables upscaling of monolithic perovskite/silicon heterojunction tandem cells, resulting in a 12.96 cm(2) monolithic tandem cell with a steady-state efficiency of 18%.

This work presents the influence of the intrinsic and doped amorphous silicon layers on the properties of a silicon heterojunction solar cell. Thickness series of all amorphous silicon layers were performed in both front and rear emitter to measure the impact of a given layer on the surface defect passivation, on the charge transport throughout the cell structure and on contact selectivity. Temperature dependent lifetime and IV measurements were performed to get an in depth understanding of the passivation mechanisms and of the effects of band offsets on charge extraction. Eventually, correlation between the different layers were evidenced. This study provides guidelines on the ideal structure for the fabrication of high-efficiency heterojunction solar cells, showing up to 22.7% efficiencies with devices employing standard PECVD amorphous silicon layers, industry-relevant ITO and screen printed silver as TCO and front metallization. It also gives insights on the best design to achieve a high energy yield for specific locations, exploiting the eventual improvements in efficiency for different irradiance and temperature when appropriate layer stacks are employed. Experimental details For this study, standard heterojunctions were fabricated using 240-μm-thick textured n-type float zone silicon wafers (2.8 Ωcm). Intrinsic and doped amorphous silicon layers were deposited by PECVD, then ITO and silver were sputtered to form 2x2 cm cells where the front silver contacts were screen printed. The injection-dependent minority carrier lifetime was measured after PECVD, and temperatureand illuminationdependent IV and EQE measurements were performed on cells. Series resistance and ideality factor were also extracted to unravel their respective roles on the fill factor.

Perovskite and silicon solar cells have recently been shown to be perfect partners for tandem devices with potentially very high efficiency at low additional costs over standard silicon cells. Here, we present the development of efficient perovskite top cells suitable for 4-terminal and monolithic tandem integration on silicon heterojunction bottom cells. We show a 4-terminal tandem measurement with 25.6% efficiency on small cells and 23.2% on a 1 cm 2 fully integrated device. Monolithic tandems with >20% efficiencies were developed on several types of silicon wafers, allowing for a direct optical comparison. We identify parasitic absorption to be the limiting factor for high performance and discuss several practical solutions to reduce them.