Carrier‐selective contact‐based silicon heterojunction solar cells are fabricated using nickel oxide (NiOx) as a hole‐selective layer by thermal evaporation. The highest power conversion efficiency of ≈15.20% with a chemically grown SiOx interlayer is achieved from a Ag/ITO/NiOx/n‐Si/LiFx/Al cell structure in comparison with ≈12.43% without SiOx. The cells without and with the SiOx layer are analyzed by considering crucial parameters for conversion efficiency, such as minority carriers' diffusion lengths, lifetimes, recombination resistance, and density of interface defect states at the NiOx/n‐Si junction, by studying the dark/light current density–voltage, quantum efficiency, impedance, and parallel conductance characteristics. Device analysis provides evidence for the cell's open‐circuit voltage and short‐circuit current enhancement with the SiOx interlayer. This is due to an improvement in minority carrier lifetimes from ≈8.6 to ≈48.27 μs (photo‐conductance decay analysis), which is also estimated from ≈7.45 to ≈49.20 μs by impedance spectra analysis, increased minority carrier diffusion length from ≈171 to ≈952 μm, and decreased rear surface recombination velocity from ≈1106 to ≈170 cm s−1 (quantum efficiency analysis). These investigations reveal that engineering the n‐Si/LiFx interface by the SiOx interlayer is more important than the NiOx/n‐Si interface because of a thin unintentionally grown SiOx layer during NiOx evaporation simultaneously mediating silicon surface passivation.

For the broad use of solar photovoltaic devices, the device fabricated at commercially viable silicon wafers at room temperature is more preferable to harvest abundant solar energy. Silicon heterojunction solar cells at room temperature, based on carrier-selective layers without using any specified surface passivation layer on the silicon wafer is fabricated. Industrially feasible Cz n-type non-textured silicon wafers having the bulk lifetime of 300 ms are used for cell fabrication. The molybdenum oxide (MoO x ) and lithium fluoride (LiF x ) are used as hole-and electron-selective layers, respectively. The highest conversion efficiency of >15% from the simple architecture of Ag/TCO/MoO x /n-Si/LiF x /Al is achieved. The internal quantum efficiency of %96% is observed in the shorter wavelength region, whereas to understand relatively less response between 800 and 1100 nm wavelength region; effective minority carrier diffusion lengths are estimated. The authors also confirm the inversion layer formation in the silicon after MoO x contact from temperature dependent capacitance-voltage measurements, and quantify the crucial built-in-potential of %0.69 V from the cell structure due to the high work function of MoO x layer.

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