We characterize and discuss the impact of hydrogenation on the performance of phosphorus-doped polycrystalline silicon (poly-Si) films for passivating contact solar cells. Combining various characterization techniques including transmission electron microscopy, energy-dispersive X-ray spectroscopy, low-temperature photoluminescence spectroscopy, quasi-steady-state photoconductance, and Fourier-transform infrared spectroscopy, we demonstrate that the hydrogen content inside the doped poly-Si layers can be manipulated to improve the quality of the passivating contact structures. After the hydrogenation process of poly-Si layers fabricated under different conditions, the effective lifetime and the implied open circuit voltage are improved for all investigated samples (up to 4.75 ms and 728 mV on 1 Ω cm n-type Si substrates). Notably, samples with very low initial passivation qualities show a dramatic improvement from 350 μs to 2.7 ms and from 668 to 722 mV.

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.

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One of the most fundamental parameters of any photovoltaic material is its quasi‐Fermi level splitting (∆µ) under illumination. This quantity represents the maximum open‐circuit voltage (Voc) that a solar cell fabricated from that material can achieve. Herein, a contactless, nondestructive method to quantify this parameter for atomically thin 2D transition metal dichalcogenides (TMDs) is reported. The technique is applied to quantify the upper limits of Voc that can possibly be achieved from monolayer WS2, MoS2, WSe2, and MoSe2‐based solar cells, and they are compared with state‐of‐the‐art perovskites. These results show that Voc values of ≈1.4, ≈1.12, ≈1.06, and ≈0.93 V can be potentially achieved from solar cells fabricated from WS2, MoS2, WSe2, and MoSe2 monolayers at 1 Sun illumination, respectively. It is also observed that ∆µ is inhomogeneous across different regions of these monolayers. Moreover, it is attempted to engineer the observed ∆µ heterogeneity by electrically gating the TMD monolayers in a metal‐oxide‐semiconductor structure that effectively changes the doping level of the monolayers electrostatically and improves their ∆µ heterogeneity. The values of ∆µ determined from this work reveal the potential of atomically thin TMDs for high‐voltage, ultralight, flexible, and eye‐transparent future solar cells.

a very recent family of 2D nanomaterials, depth optical and optoelectronic studies of various 2D MXenes have been lacking yet. Similar to early demonstrated graphene, and TMD-based quantum dots (QDs), [4] a few research groups have introduced the synthesis of MXene (Ti 3 C 2 T x , T x = F 2 , (OH) 2) QDs via a solvothermal technique with etching Al atoms from the commercially available Ti 3 AlC 2. [5] In the same regard, we have also developed a simple and cost effective synthesis of Ti 3 C 2 T x QDs via chemical solution method, which follows the long-time magnetic stirring process initiated etching of Al atoms from commercial Ti 3 AlC 2 powder at room temperature. Such 2D material-based QDs are found effective for various optical and photonics applications. [6] The scientific investigations of lightmatter interactions and many body correlations have been highly fascinating research topics since a decade ago. The monolayer of TMDs provides a unique platform for such interactions, [7-9] which leads to the formation of many excitonic complexes. In particular, the reduced dielectric screening and strong Coulomb interaction in the monolayer of TMDs generate tightly bound high binding energy excitonic systems. [7] Moreover, excitons residing in the two different valleys at the K point of the Brillouin zone can also interact in the presence of a high density of excitons, [9,10] and facilitate the formation of high order excitons. In this regard, tightly bound biexcitons have been experimentally demonstrated in TMD monolayers, in WS 2 , WSe 2 , and MoS 2 monolayers. [11,12] However, the binding energies of these biexcitons determined in the range of 50−70 meV are 1 order higher in magnitude than the theoretically predicted values. [13] To resolve this discrepancy, Zhang et al. postulated the concept of excited state biexciton with the consideration that the biexciton structure as a charge is attached to the tail of a trion instead of four particles (e − h + e − h +) symmetric state, and calculated the binding energy of TMDs monolayer in the range of experimental value. [14] This postulate was furthermore experimentally validated in suspended MoSe 2 monolayer. [15] However, very recently, a few research groups independently reported the existence of four particles symmetric state of biexcitions in WSe 2 , [16-18] WS 2 , [18] and MoSe 2 , [19] monolayer, which is same as the earlier theoretical prediction. [13] These studies confirmed the formation Since the Ti 3 C 2 was discovered in 2011, the family of MXenes has attracted much attention. MXenes offer great potential in the tuning of many fundamental properties by the synthesis of new structures. The synthesis methods of MXene mainly require steps including immersing a MAX phase in hydrofluoric acid (HF) and processing at high temperatures. However, the HF may be hard to acquire in many countries and processing at high temperatures may cause risk issues. In this article, a simple and cost-effective synthesis of Ti 3 C 2 T x quantum dots (QDs) via chemical solution meth...