Combining electron‐ and hole‐selective materials in one crystalline silicon (Si) solar cell, thereby avoiding any dopants, is not considered for application to photovoltaic industry until only comparable efficiency and stable performance are achievable. Here, it is demonstrated how a conventionally unstable electron‐selective contact (ESC) is optimized with huge boost in stability as well as improved electron transport. With the introduction of a Ti thin film between a‐Si:H( i )/LiF and Al electrode, high‐level passivation ( S eff = 4.6 cm s –1 ) from a‐Si:H( i ) and preferential band alignment ( ρ C = 7.9 mΩ cm 2 ) from low work function stack of LiF/Ti/Al are both stably retained in the newly constructed n ‐Si/a‐Si:H( i )/LiF/Ti/Al ESC. A detailed interfacial elements analysis reveals that the efficiently blocked inward diffusion of Al from electrode by the Ti protecting layer balances transport and recombination losses in general. This excellent electron‐selective properties in combination with large process tolerance that enable remarkable device performance, particularly high efficiencies of 22.12% and 23.61%, respectively, are successfully approached by heterojunction solar cells with dopant‐free ESC and dopant‐free contacts for both polarities.

Specific contact resistance (ρC) plays a significant role in determining the efficiency of dopant‐free heterojunction (DFHJ) silicon solar cells. Existing methods allow accurate measurement of ρC only in the majority carrier collection region. Herein, taking the heterojunctions of transition metal oxide/c‐Si(n) as an example, how to extract ρC from the minority carrier (hole) collection region by ingeniously using the expanded Cox and Strack method is demonstrated. On the basis of technology computer‐aided design and a double (diode + resistance) equivalent circuit model, the improved method can separate the electron current density and hole current density from each other and thus the corresponding resistance for both polarities can be well determined. The effectiveness of the improved method in precisely extracting the corresponding ρC is further verified by a series of experimental examples. A general method of unambiguously extracting specific contact resistance in DFHJ silicon solar cells is established.

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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.