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 ( ρ c ) between the Mg(Acac) 2 /Mg/Ag electron‐selective heterocontacts and n‐type c‐Si substrates are lower than 10 mΩ cm 2 , 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.
The radial dose distribution in water and silicon for ions with a wide range of energies, and the energy dissipation of normally incident electrons of energies 0.025, 0.1, 1 and 10 MeV in C, Al, Cu, Sn and Pb have been calculated on the basis of classical collision dynamics and a general logarithmic polynomial range-energy relationship. The results of the present work almost agree well with Monte Carlo calculations and measured data.
Emission of secondary electrons induced by the passage of low energy positrons through thin carbon foils was studied by the Monte Carlo method. The positron and electron elastic cross sections were calculated by partial wave analysis. The inelastic positron-valence-electron was described by the energy loss function obtained from dielectric theory. The positron-core-electron interaction was modelled by the Gryzinski's excitation function. Positron transport inside the carbon foil was simulated in detail. Secondary electrons created by positrons and high energy secondary electrons through inelastic interactions were tracked through the foil. The positron transmission coefficient and secondary electron yielded in forward and backward geometry are calculated and dependences on positron energy and carbon foil thickness are discussed.
Abstract Crystalline silicon (c‐Si) solar cells featuring carrier‐selective passivating contacts have become a prominent path to develop highly efficient photovoltaic devices. Development of electron‐selective materials that can provide excellent surface passivation and low contact resistivity to c‐Si substrates while presenting good environmental stability is crucial for practical implementation. Here, an easy approach is demonstrated to achieve low resistivity Ohmic contacts between slightly doped n‐type c‐Si and aluminum electrodes via simple spin‐coating of metal acetylacetone (MAcac) film on a c‐Si surface. Contact resistivity of 1.3 m Ω cm 2 (18.2 m Ω cm 2 with an a‐Si:H(i) passivating layer) is realized when a thin calcium acetylacetone (CaAcac) interlayer is introduced between c‐Si and Al. An n‐Type c‐Si solar cell with a full area rear a‐Si:H(i)/CaAcac/Al electron‐selective contact is demonstrated with a power conversion efficiency of 21.6%. This work not only demonstrates an approach to develop highly efficient n‐type c‐Si solar cells with effective electron‐selective passivating contacts, but also contributes toward accomplishing a simplified fabrication process for photovoltaic devices, from vacuum to solution processing.
Crystalline silicon solar cells produced by doping processes have intrinsic shortages of high Auger recombination and/or severe parasitic optical absorption. Dopant-free carrier-selective contacts (DF-CSCs) are alternative routines for the next generation of highly efficient solar cells. However, it is difficult to achieve both good passivating and low contact resistivity for most DF-CSCs. In this paper, a high-quality dopant-free electron-selective passivating contact made from ultra-low concentration water solution is reported. Both low recombination current (J0) ~10 fA/cm2 and low contact resistivity (ρc) ~31 mΩ·cm2 are demonstrated with this novel contact on intrinsic amorphous silicon thin film passivated n-Si. The electron selectivity is attributed to relieving of the interfacial Fermi level pinning because of dielectric properties (decaying of the metal-induced gap states (MIGS)). The full-area implementation of the novel passivating contact shows 20.4% efficiency on a prototype solar cell without an advanced lithography process. Our findings offer a very simple, cost-effective, and efficient solution for future semiconductor devices, including photovoltaics and thin-film transistors.
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