Interface Characterization and Electrical Transport Mechanisms in a-Si:H/c-Si Heterojunction Solar Cells

Abstract

The fabrication of amorphous silicon/crystalline silicon ͑a-Si:H/c-Si͒ heterojunction solar cell and an understanding of the fundamental conduction mechanism in the device are presented. In the first part, the effect of intrinsic amorphous silicon ͓a-Si:H͑i͔͒ layer thickness on the performance of a-Si:H/c-Si solar cells has been studied. The thickness of a-Si:H͑i͒ layer formed on n-type c-Si substrate was controlled accurately with spectroscopy ellipsometry ͑SE͒. Based on SE results, we discuss the influence of the a-Si:H͑i͒ thickness on the interface quality and thereby cell performance. Then, in the latter part, we present the temperaturedependent current density-voltage curves, in the dark, in order to elucidate the dominant transport mechanisms in a-Si:H/c-Si heterojunction solar cells with and without incorporation of a-Si:H͑i͒ layers. Finally, using optimum design considerations, we obtained a solar cell efficiency of 17.43%.

Dopant-free multilayer back contact silicon solar cells employing V2Ox/metal/V2Ox as an emitter

“…Finally, the MLBC solar cell employing a VMV (12 nm Ca) emitter exhibited the lowest value of E a , which may be explained by the fact that the increased recombination in the VMV (12 nm Ca) emitter bulk is due to the existence of a large Schottky barrier and reverse bias. 30 Consequently, the use of a VMV (12 nm Ag) as an emitter in an MLBC solar cell can provides the largest value of E a (E a ¼ 0.75 eV) of all the emitters considered, which is also in good agreement with the increased V OC shown in Fig. 3(d).…”

“…5(c), the diffusion-recombination model is dominant at the interface of VMV (Ag)/n-Si and VMV (Au)/n-Si contacts due to the increase in the exponential factor A with increasing 1/kT. 29,30 Meanwhile, the multi-tunneling capture emission (MTCE) model determined the charge carrier transport property between V 2 O x /n-Si and VMV (Ca)/n-Si contacts at a high forward-bias voltage because the A values remain fairly stable with increasing 1/kT. 31 The MTCE process is more related to the bulk recombination in the emitter than to interface defect states, and, thus, the use of VMV (Ca) as an emitter produces a larger recombination rate and lower V OC , as shown in Fig.…”

Current transport studies of amorphous n/p junctions and its application in a‐Si:H/HIT‐type tandem cells

“…These E a( J 0) values are less than kT at room temperature and are also less than the energy band gap of a‐Si:H(n) and a‐Si:H(p). Thus, the dominant carrier transports in the n/p junction cannot be the direct tunneling through the barrier . We propose the MTCE model for the present system.…”

Electrical Interface Characterization of Ultrathin Amorphous Silicon Layers on Crystalline Silicon

“…A band bending will occur at the heterojunction and will certainly influence the barrier height at the interface. However, Dao et al [ 19 ] suggested that for interfaces with a high defect density, defect states within the bandgap play a significant role with respect to the barrier height. Therefore, our measured barrier height represents an “effective” barrier height considering band bending, band offset, bandgap widening, and defect state density.…”