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Herein, an optical loss analysis of the recently introduced silicon carbide–based transparent passivating contact (TPC) for silicon heterojunction solar cells is presented, the most dominant losses are identified, and the potential for reducing these losses is discussed. Magnesium fluoride is applied as an antireflective coating to reduce the reflective losses by up to 0.8 mA cm−2. When applying the magnesium fluoride, the passivation quality of the layer stack degrades, but is restored after annealing on a hot plate in ambient air. Afterwards, a road map for TPC solar cells toward an efficiency of 25% is presented and discussed. The largest part in efficiency gain is achieved by reducing the finger width and by increasing the passivation quality. Furthermore, it is shown that TPC solar cells have the potential to achieve short‐circuit current densities above 42 mA cm−2 if the finger width is reduced and the front‐side indium tin oxide (ITO) layer can be replaced by an ITO silicon nitride double layer. [ABSTRACT FROM AUTHOR]

In this work, we propose a route to achieve a certified efficiency of up to 24.51% for silicon heterojunction (SHJ) solar cell on a full‐size n‐type M2 monocrystalline‐silicon Cz wafer (total area, 244.53 cm2) by mainly improving the design of the hydrogenated intrinsic amorphous silicon (a‐Si:H) on the rear side of the solar cell and the back reflector. A dense second intrinsic a‐Si:H layer with an optimized thickness can improve the vertical carrier transport, resulting in an improved fill factor (FF). In order to reduce the plasmonic absorption at the back reflector, a low‐refractive‐index magnesium fluoride (MgF2) is deposited before the Ag layer; this leads to an improved gain of short circuit current density (Jsc). In total, together with MgF2 double antireflection coating and other fine optimizations during cell fabrication process, ~1% absolute efficiency enhancement is finally obtained. A detailed loss analysis based on Quokka3 simulation is presented to confirm the design principles, which also gives an outlook of how to improve the efficiency further. [ABSTRACT FROM AUTHOR]

The organic passivated carbon nanotube (CNT)/silicon (Si) solar cell is a new type of low‐cost, high‐efficiency solar cell, with challenges concerning the stability of the organic layer used for passivation. In this work, the stability of the organic layer is studied with respect to the internal and external (humidity) water content and additionally long‐term stability for low moisture environments. It is found that the organic passivated CNT/Si complex interface is not stable, despite both the organic passivation layer and CNTs being stable on their own and is due to the CNTs providing an additional path for water molecules to the interface. With the use of a simple encapsulation, a record power conversion efficiency of 22% is achieved and a stable photovoltaic performance is demonstrated. This work provides a new direction for the development of high‐performance/low‐cost photovoltaics in the future and will stimulate the use of nanotubes materials for solar cells applications. [ABSTRACT FROM AUTHOR]

To improve the infrared (IR) response, a high‐refractive‐index intrinsic amorphous silicon (a‐Si:H) layer is introduced after metallization of bifacial silicon heterojunction (SHJ) solar cells, resulting in a transparent conductive oxide (TCO)/a‐Si:H back reflector, which functions like distributed Bragg reflector (DBR). This concept is demonstrated by both Sentaurus Technology Computer‐Aided Design (TCAD) simulation and experimental methods. The TCO/a‐Si:H back reflector can increase rear internal reflectance by reducing the transmission loss, thus improving the IR external quantum efficiency. The using of Sn‐doped In2O3 (ITO)/a‐Si:H back reflector in >23.5% efficiency SHJ solar cells can improve short‐circuit current density by 0.4 mA cm−2 which is quite similar as using the more expensive ITO/Ag back reflector, while keeping a cell bifaciality of 55%. This brings its advantage for monofacial application case. Future studies would be nice to work on higher transparent back reflectors to broaden the application in bifacial case. This back‐reflector design promotes IR response of SHJ solar cells with transferring to a wide variety of TCOs. [ABSTRACT FROM AUTHOR]

One of the challenges in fabricating high‐performance n‐type silicon heterojunction (SHJ) solar cells is developing a high‐quality transparent conductive oxide (TCO) electrode. Herein, the development and application of low‐temperature sputtered titanium‐doped indium oxide (ITiO) in n‐type, rear junction SHJ solar cells as a function of the oxygen flow ratio is presented. The microstructure, morphology, and optoelectronic properties are analyzed. The grain size of ITiO thin films decreases rapidly as the oxygen flow ratio is increased. Compared with an indium tin oxide (ITO) thin film, ITiO shows a superior balance in achieving excellent optoelectronic properties by reducing film resistivity but maintaining weak absorption. Higher fill factor is obtained by substituting ITiO for ITO as the front electrode in SHJ solar cells, which is mainly due to the improved carrier transport. Resistivity contributions of front‐side vertical and lateral carrier transport are disclosed by Quokka3 simulation. A champion cell efficiency of 23.81% with ITiO is achieved, which is so far the highest efficiency among the application of ITiO in SHJ solar cells to the best of our knowledge. The study demonstrates that ITiO is a promising TCO candidate for SHJ solar cells. [ABSTRACT FROM AUTHOR]

One of the challenges in fabricating high‐performance n‐type crystalline silicon (n‐type c‐Si) solar cells is the high‐quality n‐type c‐Si/metal contact. Schottky barriers are commonly found on the n‐type c‐Si/metal contact, which suppresses electron transportation. Herein, novel stacks of magnesium acetylacetonate (Mg(Acac)2)/magnesium (Mg)/silver (Ag) to form electron‐selective contacts for n‐type c‐Si solar cells are presented, which enables a dopant‐free process. An ohmic contact on n‐type c‐Si is formed using the Mg(Acac)2/Mg/Ag stacks. The transmission spectrum and ultraviolet photoelectron spectroscopy measurements show negligible conduction‐band offset and large valence‐band offset between Mg(Acac)2 and n‐type c‐Si, which indicates the electron‐transporting and hole‐blocking properties of Mg(Acac)2/n‐type c‐Si heterocontacts. Moreover, the contact resistivities (ρc) between the Mg(Acac)2/Mg/Ag electron‐selective heterocontacts and n‐type c‐Si substrates are lower than 10 mΩ cm2, which demonstrates the good electrode properties of the Mg(Acac)2/Mg/Ag stacks. The Mg(Acac)2/Mg/Ag electron‐selective stacks are applied on n‐type c‐Si solar cells with partial rear contact, and >20% efficiency is achieved, which is higher than that in a reference cell with only Ag contact. The stability of the n‐type c‐Si solar cell performance equipped with Mg(Acac)2/Mg/Ag contacts is verified under ambient conditions. This novel low‐temperature contact technique offers a reliable alternative for high‐performance n‐type c‐Si solar cells. [ABSTRACT FROM AUTHOR]

N‐type microcrystalline silicon carbide (μc‐SiC:H(n)) is a wide bandgap material that is very promising for the use on the front side of crystalline silicon (c‐Si) solar cells. It offers a high optical transparency and a suitable refractive index that reduces parasitic absorption and reflection losses, respectively. In this work, we investigate the potential of hot wire chemical vapor deposition (HWCVD)–grown μc‐SiC:H(n) for c‐Si solar cells with interdigitated back contacts (IBC). We demonstrate outstanding passivation quality of μc‐SiC:H(n) on tunnel oxide (SiO2)–passivated c‐Si with an implied open‐circuit voltage of 742 mV and a saturation current density of 3.6 fA/cm2. This excellent passivation quality is achieved directly after the HWCVD deposition of μc‐SiC:H(n) at 250°C heater temperature without any further treatments like recrystallization or hydrogenation. Additionally, we developed magnesium fluoride (MgF2)/silicon nitride (SiNx:H)/silicon carbide antireflection coatings that reduce optical losses on the front side to only 0.47 mA/cm2 with MgF2/SiNx:H/μc‐SiC:H(n) and 0.62 mA/cm2 with MgF2/μc‐SiC:H(n). Finally, calculations with Sentaurus TCAD simulation using MgF2/μc‐SiC:H(n)/SiO2/c‐Si as front side layer stack in an IBC solar cell reveal a short‐circuit current density of 42.2 mA/cm2, an open‐circuit voltage of 738 mV, a fill factor of 85.2% and a maximum power conversion efficiency of 26.6%. [ABSTRACT FROM AUTHOR]

• An increase of the carrier density and mobility can be achieved by using hydrogen during the sputtering process, ascribed to the additional H dopants in the films and passivation in the grain boundary. • Compared with reducing the oxygen gas flow, putting small amount of hydrogen into the sputtering mixture gases could be a better strategy to balance the electrical and optical properties of the ITO layers. • A degradation of both field-effect and chemical passivation quality was obtained for experimental devices with hydrogenated ITO, attributed to the etching effect of H on a-Si:H(n) and more effusion of H from a-Si:H(i) layer into ITO layers. • A significant improvement of FF (∼1.1 % abs) with sacrifice of J sc (∼0.3 mA/cm2) were obtained at 2% of f H2 and 0.8 Pa of pressure, yielding 0.18 % abs gain of efficiency. • The best solar cell with hydrogenated ITO exhibits η of 22.97%, V oc of 735 mV, FF of 82.15% and J sc of 38.03 mA/cm2. The influence of the oxygen flow ratio (f O2) and hydrogen flow ratio (f H2) on the optoelectronic properties of the indium tin oxide (ITO) films are studied together. An increase of the carrier density and mobility can be achieved by using hydrogen during the sputtering process, resulting in an improvement of the film conductivity. Compared with reducing the oxygen gas flow, putting small amount of hydrogen into the sputtering mixture gases could be a better strategy to balance the electrical and optical properties of the ITO layers. Quokka3 simulation demonstrates 0.1 % abs improvement of power conversion efficiency (η) at 2% of f H2 compared to reference based on the ITO material properties. Full-size M2 solar cells with various ITO layers were fabricated. A degradation of passivation quality for the devices with hydrogenated ITO (ITO:H) was observed after sputtering process, ascribed to the etching effect of hydrogen radicals on the amorphous silicon (a-Si:H) layer and the extraction of hydrogen from a-Si:H (i) to ITO layers. It is proved that this sputter damage can be eliminated by increasing the pressure of ITO:H above 0.5 Pa. Finally, a ∼ 0.18% gain of η was obtained at f H2 of 2% and pressure of 0.8 Pa and the best cell shows the η of 22.97%, V oc of 735 mV, FF of 82.15% and J sc of 38.03 mA/cm2. [ABSTRACT FROM AUTHOR]

• 10.72% efficiency c-Si solar cell is achieved with totally low-temperature processes. • In 2 S 3 is proved an excellent electron-selective contact material for c-Si solar cells. • In 2 S 3 thin films were deposited by a simple thermal evaporation process. • The crystal structures, optical and composition properties of In 2 S 3 were studied. Dopant-free carrier-selective contacts have gained attention for application in silicon solar cells because of their simpler preparation process and low-temperature fabrication. However, there were few reports on efficient p-Si solar cells having dopant-free electron contacts. In this study, indium sulfide (In 2 S 3) thin films were successfully deposited by simple thermal evaporation at room temperature and used as dopant-free electron-selective contacts on the front side of p-Si heterojunction solar cells. The changes in crystal structures, optical properties, compositions, and energy-band structures of the In 2 S 3 thin films due to different annealing temperatures were investigated. The champion conversion efficiency of 10.72% was achieved with lightly doped, textured front Czochralski (Cz) p-Si wafers, and a low thermal energy cost. This study demonstrates that In 2 S 3 film is an effective electron-selective contact for silicon solar cells, providing an alternative simple process to the fabrication of dopant-free optoelectronic devices. [ABSTRACT FROM AUTHOR]

The dopant-free back contact solar cells are demonstrated based on hole selective contact material, chromium trioxide (CrO x , x < 3) with a low melting point for high stability and high performance. In this contribution, CrO x is first applied in silicon based solar cell as the emitter. Integrating 5 nm CrO x and 2 nm LiF x into solar cell as the emitter and the back surface filed, resulted in a device efficiency of 13.6%. For further improvement, the back contact solar cell reaching an efficiency of 15.8% was fabricated, by implementing the multilayer films of CrO x (5 nm)/Au (4 nm)/ CrO x (5 nm) as the emitter. The formation of Cr(OH) 3 in ambient condition, resulted in a lower work function (4.8 eV) of the CrO x film. Furthermore, the multilayer back contact solar cell demonstrated a high stability due to CrO x covered with 500 nm Ag, when stored in ambient air longer than 170 days. [ABSTRACT FROM AUTHOR]