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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. [ABSTRACT FROM AUTHOR]

The challenge of Fermi-level pinning significantly complicates the establishment of Ohmic, low-resistance contacts for lightly doped n-type crystalline silicon (c-Si), a critical requirement for economically feasible device development. In this novel study, we present an innovative approach by introducing an ultra-thin zirconium oxide (ZrO x) film to achieve an Ohmic contact in n-type c-Si. The ZrO x films are deposited through e-beam evaporation at room temperature, and their properties are characterized using spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and contact resistivity (ρ c) measurements. Our investigation unveiled a pronounced dependence of the contact resistivity on the thickness of the ZrO x layer, with the lowest ρ c value of 22 mΩ cm2 achieved with an ultrathin 1 nm ZrO x film. To demonstrate our study's feasibility, we applied ZrO x as an electron-selective rear-side contact layer in a lightly doped n-type c-Si solar cell with a boron-diffused emitter on the front side. This yielded a photovoltaic conversion efficiency (PCE) of 16% and a notable fill factor (FF) exceeding 79%. These findings clearly emphasized the significant promise of ZrO x as an emerging and highly effective electron-selective contact layer for lightly doped n-type c-Si devices. [ABSTRACT FROM AUTHOR]

We present the feasibility of integrating substoichiometric molybdenum oxide (MoOx) as hole‐selective rear contact into the production sequence of industrial scale p‐type crystalline silicon (c‐Si) solar cells. Thin films of MoOx are deposited directly on p‐type c‐Si by thermal evaporation at room temperature. It is found that Ag/MoOx/p‐type c‐Si rear contact structure exhibits low contact resistivity and modest surface recombination current density. The attained peak efficiency (η) of the fabricated solar cells is 17.65% with Voc of 626 mV, Jsc of 36.8 mA/cm2, and fill factor (FF) of 76.63%. Next, a complete loss analysis of a MoOx/p‐type Si heterojunction solar cell is carried out for the first time by using Quokka simulation software that employs characteristics of different layers which constitute the fabricated solar cell. Based on this loss analysis, the dominant loss mechanisms are defined and a roadmap to attain the desired highest possible efficiency from industrial scale p‐type c‐Si solar cells with full‐area MoOx hole‐collecting rear contact is explored. [ABSTRACT FROM AUTHOR]

In this study, we report on the passivation quality of atomic layer deposition grown ultra-thin Al2O3 and Al2O3 capped with plasma-enhanced chemical vapor deposition deposited SiNx on Cz p-type wafers for the rear side of a passivated emitter and rear cell (PERC). Different activation recipes using N2, forming gas (FG), and two-step annealing for different durations are investigated before SiNx deposition. The effect of different Al2O3 thicknesses and corresponding activation processes on the Al2O3/SiNx passivation performance, after a high temperature firing step, is studied to reach a new optimization toward higher efficiency and lower cost. A record high iVoc of 720 mV is obtained after firing step from Al2O3/SiNx stacks with Al2O3 thickness as thin as ∼2 nm with FG annealing. Our results demonstrate that, under well-optimized process conditions, ultra-thin Al2O3 thicknesses provide superior passivation quality as compared to the larger thicknesses which are commonly applied in the PERC industrial line and the potential for further improvement of industrial PERC solar cells in terms of cost reduction and efficiency. [ABSTRACT FROM AUTHOR]

Summary: Conventional silicon heterojunction solar cells employ defects‐prone a‐Si:H layers for junction formation and passivation purposes. Substituting these layers with hole‐selective MoOx and electron‐selective TiOx can reduce parasitic absorption and energy band offsets issues associated with doped silicon films. In this work, dopant‐free asymmetric heterostructure Si solar cells are studied with and without SiO2 passivation layer, and their performance has been compared. The inclusion of ultrathin SiO2 insulator as a passivation layer promotes significant band bending that induces interface inversion of crystalline silicon as well as maintains the electric field required to tunnel charge carriers. The energy band diagram studies and variation of oxide thickness show that the IV characteristics of the solar cell critically depend on the insulator thickness; as the carriers tunnelling through the insulator becomes negligible at larger thicknesses. The simulated structure with MoOx as front hole‐selective contact and without any passivation exhibited conversion efficiency of 15.73%, which improved to 18.69% by incorporating passivated a‐Si:H. However, by employing rear SiO2/TiOx stack with the front SiO2/MoOx, the device performance enhanced to open‐circuit voltage of 785 mV, short‐circuit current density of 41 mA/cm2, fill factor of 77%, and simulated conversion efficiency of 24.83%, which is ∼10% enhancement in the performance as compared to reference device employing traditional a‐Si:H with dopant‐free films. Novelty Statement: For the first time, a dopant‐free asymmetric silicon heterostructure solar cell (DASH) employing silicon oxide (SiO2) as a passivation layer has been physically modelled using Silvaco TCAD. The dopant‐free MoOx and TiOx as hole‐ and electron‐selective contacts have been incorporated. An ultrathin SiO2 promotes band bending that induces interface inversion of absorber as well as facilitating carrier tunnelling. An efficiency of 24.83% has been numerically attained which is the best performance among DASH structures designed with oxide passivation. The 2‐D cross‐section view of the proposed device employing dopant‐free layers and oxide passivated film is illustrated in Figure 1 for which we have applied memory intensive numerical method based on the computation of Poisson, charge transport and continuity equations in the Silvaco ATLAS module. In order to undertake in‐depth analysis of the proposed structure, a simple device based on MoOx/cSi wafer was first designed and simulated in order to understand the charge transport behaviour. The electrical and optical parameters for various layers have been shown in the Table and the current density due to tunnelling of charge carriers across Silicon oxide (SiO2) passivated layer has been calculated via Fowler‐Nordheim approximation. The reference structure with traditional intrinsic a‐Si:H has also been simulated. [ABSTRACT FROM AUTHOR]

Surface texturing of transparent conducting oxides and plasmonic interfaces are two important techniques used separately in thin film solar cells to reduce reflection and enhance light-trapping. In this study, we merge the effects of Al:ZnO surface texturing and Ag nanoparticles (AgNPs) plasmonics in a single light-trapping interface to investigate their combined light trapping efficiency on a-Si:H thin film. Light scattered by this interface is optimized by placing a thin SiO2 spacer layer between AgNPs and a-Si:H absorber layer. Our results indicate that the AgNPs embedded in SiO2 significantly enhance absorption at energies close to the band gap of a-Si:H. Surface texturing by wet etching of Al:ZnO combined with AgNP produces the highest optical extinction of a- Si:H thin film at the band edge. Furthermore, the measured photocurrent in a-Si:H shows a clear increase not only at AgNPs resonance wavelength but over the entire wavelength range. (a) Superstrate configuration of a-Si:H thin film on Al:ZnO, (b) diffuse scattered light by textured Al:ZnO, (c) scattering by plasmonic metal nanoparticles, and (d) double light scattering by plasmonic metal nanoparticles and textured Al:ZnO. [ABSTRACT FROM AUTHOR]

In this study, aluminum induced texturing (AIT) technique is used to increase light absorption in thin film by way of increasing the portion of the diffuse transmitted light (haze). For this purpose, various AIT process parameters such as starting aluminum thicknesses, annealing temperature and time, etching time, etchant's concentrations, and temperature of etching are known to affect the final texture. We have investigated the effect of aluminum thickness and etching time on AIT process while keeping the other parameters fixed. Our results show that by changing initial aluminum thickness and etching time, it is possible to control surface morphology of glass substrate and the resulting optical diffuse transmittance. In addition, diffuse transmittance is increased over the visible range of solar spectra and total absorption by a-Si:H is increased. [ABSTRACT FROM AUTHOR]

Aluminum doped zinc oxide (AZO) thin films are prepared on ultra-thin flexible glass and flexible polyethylene terephthalate (PET) substrates at room temperature by radio frequency (RF) magnetron sputtering. Optimization of films has been achieved by varying process parameters to reach the demands of proper conductive layer for thin silicon solar cell applications. Structural analysis of the films was done by X-ray diffraction spectroscopy. Optical and electrical properties of the films were carried out by means of UV-Visible spectroscopy, and four point probe measurements. Thickness of the films was obtained by spectroscopic ellipsometry. Transmission measurements clearly show that by decreasing pressure transmission of the AZO film is improved in the UV region. Our results show that by varying the deposition parameters, low resistivity films of 1.1×10-3 Ωcm and 1×10-3 Ωcm were obtained on PET and on ultra-thin flexible substrates, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • High temperature firing stable n + TOPCon on textured n-type Cz c-Si wafer. • 1.2 nm SiO x / n + poly-Si maintained i V OC =720.1 mV & J 0S =3.9 fA/cm2. • The hydrogenation mechanism in n + TOPCon/AlO x is reaction limited. • TOPCon/SiN x (n = 1.96, 2.04, 2.18) and AlO x /SiN x yield the same passivation quality. Passivating contacts based on poly-Si/SiO x also referred to as TOPCon (tunnel oxide passivated contacts) have substantially improved the performance of crystalline silicon (c-Si) solar cells. Hydrogenation in TOPCon has the utmost importance for achieving high quality surface passivation and enhanced solar cell performance. In this work, the hydrogenation mechanism and high-temperature fast firing behavior of phosphorus-doped TOPCon structures, on textured crystalline Si; coated with ALD–AlO x , PECVD–SiN x , and AlO x /SiN x stacks, are investigated. Using hot plate annealing series, our results show that thermal activation for hydrogenation is required for TOPCon/AlO x , while the hydrogenation is already activated for TOPCon/SiN x. For AlO x , activation energies (E A) are calculated in the 0.28 – 0.52 eV range, implying that hydrogenation is reaction limited rather than bulk diffusion of hydrogen atoms. The effect of TOPCon layers (SiO x and poly-Si thickness, ex-situ phosphorus diffusion, AlO x /SiN x) is explored. Among all, SiO x is the most critical factor affecting the firing stability. The firing stability is achieved for TOPCon/1.2 nm SiO x with i V OC of 720.6 mV and J 0S =3.03 fA/cm2 while excellent passivation with i V OC of 735.1 mV and J 0S =2.73 fA/cm2 are not maintained in TOPCon/1.6 nm SiO x after fast firing. The reason for this stability difference is explained by the fact that higher number of interfacial defects in 1.2 nm SiO x is beneficial for preventing blister formation during fast firing. [ABSTRACT FROM AUTHOR]