Defining a parameter of plasma-enhanced CVD to characterize the effect of silicon-surface passivation in heterojunction solar cells

Abstract

The hydrogen content (C H ) and microstructure of a hydrogenated amorphous-silicon (a-Si:H) layer fabricated by plasma-enhanced chemical vapor deposition (PECVD) were analyzed to determine the effect of surface passivation on crystalline silicon (c-Si). The ratio of radio-frequency power to gas pressure (C pp in W&Pa %1 ) of the PECVD system is defined as a characterization parameter. It was found that C H and the passivation of a-Si:H layers were sensitively affected by C pp . However, C H remained almost constant at the same C pp even though the PECVD power and pressure were widely varied. We determined that an optimal region exists in the range of 0.75 < C pp < 1.25, where a high implied open-circuit voltage of 732 mV was obtained from a passivated a-Si:H/c-Si/a-Si:H structure, indicating that C pp was a useful parameter for characterizing the surface passivation effect of a a-Si:H layer on c-Si.

Improved opto-electronic properties of silicon heterojunction solar cells with SiOx/Tungsten-doped indium oxide double anti-reflective coatings

“…Amorphous and crystalline silicon (a-Si=c-Si) hetero-junction (SHJ) solar cell is a promising candidate to achieve low cost, high efficiency solar cell and module, owing to its outstandingly low recombination, high open circuit voltage (V oc ), simple structure, low process temperature and low temperature coefficient. [1][2][3][4] Panasonic has presented the world's highest cell efficiency (25.6%, designated area 143.7 cm 2 ) for back contact SHJ solar cell. 5) And this record has been increased to 26.3% by KANEKA.…”

Review—Process Research on Intrinsic Passivation Layer for Heterojunction Solar Cells

“…Nevertheless, in the presence of pressure changes, the passivation window of the passivated films shrank. The best τ eff was achieved at a hydrogen-to-silane gas flow rate ratio of 1 at the pressure of 66.7 Pa. Guo et al 33 adjusted the deposition conditions using the RF-PECVD method by varying the power from 25 W to 525 W at a specific gas pressure (100 pa, 200 pa, 300 Pa), while maintaining other parameters constant, substrate temperature of 170 °C, electrode spacing of 35 mm, gas flow rates of 50 sccm and 200 sccm for SiH 4 and H 2 , respectively. The n-type silicon wafer has an i-a-Si: H layer deposited on both sides of it without any impurity doping.…”

Plasma-deposited hydrogenated amorphous silicon films: multiscale modelling reveals key processes

“…These graphs show that the ux of physisorbed silyl radicals, their direct chemisorption and consequently the growth rate increase with the substrate temperature. According to eqn (16) shown in the ESI, † the H abstraction process in particular is responsible for the creation of dangling bonds in the absence of ion sputtering, while the chemisorption leads to the consumption of dangling bond. Then, when substrate temperature is below 450 K, chemisorption overcomes the H abstraction and hence, lower density of dangling bond sites is established.…”

“…Up to day, extensive experimental efforts were undertaken to reveal the effect of plasma-based process conditions 14 on the quality and structure of the deposited lms. 15,16 In particular, effect of plasma power density and incident precursor ux variation onto the lm structure, morphology and characteristics has been investigated with the involvement of subsequent sophisticated lm characterization. 17,18 Effect of hydrogenation was studied experimentally with the aim to better control the structure and morphology of hydrogenated silicon.…”