Surface passivation of crystalline silicon wafer via hydrogen plasma pre-treatment for solar cells

Zhang

ACS Appl. Mater. Interfaces

et al. 2014

We have investigated the role of hydrogen plasma pretreatment in promoting silicon surface passivation, in particular examining its effects on modifying the microstructure of the subsequently deposited thin hydrogenated amorphous silicon (a-Si:H) passivation film. We demonstrate that pretreating the silicon surface with hydrogen plasma for 40 s improves the homogeneity and compactness of the a-Si:H film by enhancing precursor diffusion and thus increasing the minority carrier lifetime (τ(eff)). However, excessive pretreatment also increases the density of dangling bond defects on the surface due to etching effects of the hydrogen plasma. By varying the duration of hydrogen plasma pretreatment in fabricating silicon heterojunction solar cells based on textured substrates, we also demonstrate that, although the performance of the solar cells shows a similar tendency to that of the τ(eff) on polished wafers, the optimal duration is prolonged owing to the differences in the surface morphology of the substrates. These results suggest that the hydrogen plasma condition must be carefully regulated to achieve the optimal level of surface atomic hydrogen coverage and avoid the generation of defects on the silicon wafer.

Section: Introductionmentioning

confidence: 99%

Role of Hydrogen Plasma Pretreatment in Improving Passivation of the Silicon Surface for Solar Cells Applications

Zhang

ACS Appl. Mater. Interfaces

et al. 2014

“…The substrate was immediately loaded into the sputtering chamber and exposed to FG plasma (FGP) at room temperature in order to induce hydrogen onto the substrate surface. 19) SiN x :H film was then deposited at room temperature. Tables I and II show the standard conditions of the FGP and sputtering process, respectively.…”

Section: Experimental Methodsmentioning

confidence: 99%

Single-crystal Si solar cells with pulsed-DC sputtered SiN_x:H anti-reflection film and phosphoric-acid-diffused n⁺ emitter

Yeh¹,

Wasa²

2015

Jpn. J. Appl. Phys.

A low-environmental-load single-crystal Si solar-cell fabrication method was demonstrated, in which SiN x :H anti-reflection film was formed using a pulsed-DC reactive sputtering method with Ar and a forming gas (FG: 3.8% H 2 in N 2 ), and an n + emitter was created using thermal diffusion of diluted phosphoric acid. In the SiN x :H film, it was shown that both exposure of the Si surface to FG plasma and FG annealing of the SiN x :H film dramatically decreased the surface recombination velocity, S, of the Si substrate, because of an improved Si/SiN x :H interface. The interface state density was found to be 2.1 ' 10 11 cm %2 &eV %1 and the minimum S was 72 cm&s %1 ; these values are comparable to those obtained using the plasma-enhanced chemical vapor deposition method. The characteristics of the fabricated solar cells were: a short-circuit current of 38.1 A&cm %2 , open-circuit voltage of 594.6 V, fill factor of 73.8, and an energy conversion efficiency of 16.7%.

Plasma Processes & Polymers

“…Species produced in NH 3 plasma can be used for surface etching and removing undesired oxides or deposits, such as As 2 O 3 and a‐C:H . By removing such impurities, one can achieve passivation of the material surface . Etching effects of ammonia plasma were also studied on organic low k films …”

Section: Introductionmentioning

confidence: 99%

E‐ and H‐mode transition in a low pressure inductively coupled ammonia plasma

Draškovič-Bračun

Mozetič

Zaplotnik

2017

Characteristics of ammonia plasma sustained by inductively coupled radiofrequency discharge has been studied in the range of powers between 50 and 1000 W and pressures between 10 and 90 Pa. In such an experimental setup pronounced differences between the E‐ and H‐mode were observed and explained to some details. Plasma was characterized by optical emission spectroscopy (OES) and residual gas spectrometry (RGA). The plasma luminosity changed for four orders of magnitude and the NH2 band vanished at higher powers (H‐mode). The RGA results indicated high density of NH2 radicals in the E‐mode while in the H‐mode the ammonia molecules almost entirely dissociated to H and N atoms. The N and H atoms created in the plasma recombined to the nitrogen and hydrogen molecules rather than to parent ammonia molecules on the way to the RGA.