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In this paper, the high efficiency TCO-n(aSi:H)-i(aSi:H)-p(c-Si)-$$\hbox {p}^{+}$$p+(aSi:H) heterojunction with intrinsic thin-layer (HIT) solar cell is analyzed. The effects of the intrinsic thin-layer and the back surface field (BSF) on the photovoltaic parameters of thin solar cells are discussed. The analytical results show that the intrinsic layer inserted at the a-Si:H/c-Si interface decreases the density of interface states. If the interface state density is lower than $$10^{11}\,\hbox {cm}^{-2}$$1011cm-2 in the presence of an intrinsic thin layer a-Si:H, the effect of recombination current density on the photovoltaic parameters becomes low. The BSF formed by hydrogenated amorphous silicon layer can increase the conversion efficiency by about 2.6 % and the open-circuit voltage to $$\sim $$~80 mV as compared to the HIT solar cell wherein the BSF is realized by crystalline silicon. The results obtained from the simulation studies are in good agreement with the literature, and might open promising opportunities for enhancing the design parameters of HIT cells.

The present paper accounts for a simulation study carried out to determine and optimize the effect of the high---low junction emitter front surface field (FSF) of thin heterojunction solar cell $$\text {n}^{+}$$n+(a-Si: H)/n(SiGe)/p(Si)). A theoretical model describing the behavior of heterojunction $$\text {n}^{+}$$n+---n---p type solar cells has been proposed. Besides, the expression of the photovoltaic equations allowing for the obtention of the optimal quantum efficiency of the solar cells based on the suggested model has been given. The effects of the a-Si:H-layer thickness and Ge fraction are discussed, using the computed results. The main role of an FSF layer is to reduce the effect of front surface recombination and the enhancement of light-generated free carriers' collection. This is primarily responsible for the increase of the spectral response compared with the conventional solar cell. This is achieved by the drastic reduction of the effective recombination at the emitter upper boundary and the optimum value of $$\text {n}^{+}$$n+ layer thicknesses (a-Si:H) is about 2 nm.

The present paper reports on a simulation study carried out to determine and optimize the effect of the high-low junction emitter (n+/n) of thin film SiGe/Si solar cell. The model is based on a simple analytical approach that draws on relevant device physics, including effective surface recombination velocity at the high-low junction and band discontinuities associated with heterojunctions. The collection of the light absorbed by the front surface field is discussed and an analytical solution is derived for the light-generated current in this layer. The photovoltaic parameters of SiGe/Si solar cells and those of the conventional cell Si/Si are compared. The findings revealed that the addition of Ge ~15 % to crystal Si highly enhances short-circuit current density and cell efficiency, whereas the SiGe band-gap degrades particularly the open-circuit voltage. The results also indicate that the solar cell maximum efficiency increase by about 1.7 % when the interface state density is lower than 1011 cm−2.