Crystal silicon heterojunction solar cells by hot-wire CVD

Abstract

Hot-wire chemical vapor deposition (HWCVD) is a promising technique for fabricating Silicon heterojunction (SHJ) solar cells. In this paper we describe our efforts to increase the open circuit voltage (Voc) while improving the efficiency of these devices. On p-type c-Si float-zone wafers, we used a double heterojunction structure with an amorphous n/i contact to the top surface and an i/p contact to the back surface to obtain an open circuit voltage (Voc) of 679 mV in a 0.9 cm 2 cell with an independently confirmed efficiency of 19.1%. This is the best reported performance for a cell of this configuration. We also made progress on p-type CZ wafers and achieved 18.7% independently confirmed efficiency with little degradation under prolong illumination. Our best Voc for a p-type SHJ cell is 0.688 V, which is close to the 691 mV we achieved for SHJ cells on n-type c-Si wafers.

The silane depletion fraction as an indicator for the amorphous/crystalline silicon interface passivation quality

“…Silicon heterojunction solar cells have a high conversion efficiency potential, [1][2][3][4][5] up to 23% to date. 6 The passivation of the crystalline silicon ͑c-Si͒ wafer surfaces is usually performed by very thin intrinsic amorphous silicon ͑a-Si:H͒ layers, deposited by rf plasma-enhanced chemical vapor deposition ͑PECVD͒ ͑Refs.…”

Computer Modeling of Heterojunction with Intrinsic Thin Layer “HIT” Solar Cells: Sensitivity Issues and Insights Gained

“…We find that currently, no group has been able to duplicate what Sanyo has achieved in terms of cell efficiency. Very few groups have reached beyond 19% efficiency: Helmholtz Zentrum Berlin on N-type textured wafers (Schimdt et al, 2007) and the National Renewable Energy Laboratory (NREL) on P-type textured wafers (Wang et al, 2008(Wang et al, , 2010 have achieved this feat. Good results have also been obtained by the group of EPFL, IMT, Neuchâtel, Switzrland with high open-circuit voltsge (V oc ) on flat wafers.…”

Silicon solar cells with front hetero-contact and aluminum alloy back junction

“…Silicon solar cells with a heterojunction front emitter made of thin layers of hydrogenated amorphous silicon (a-Si:H) and an a-Si:H back hetero-contact have demonstrated efficiency higher than 22% [1] and 19% [2] on high-quality n-and p-type monocrystalline silicon (c-Si), respectively. The a-Si:H has been deposited by various chemical vapor deposition (CVD) techniques and here in NREL we have focused mostly on developing and optimizing a-Si:H thin film deposited by hot-wire chemical vapor deposition (HWCVD).…”

“…One of the key advantages of the a-Si:H/c-Si hetero-interface is the low surface recombination velocity (SRV) and high Voe resulting from the low interface state density. SRV below 20 cm/sec [3] and Voc above 710 and 675 mV [2,4,5] have been consistently produced at NREL by HWCVD of double sided Si hetero-junction (SHJ) cells on n-and p-type c-Si, respectively. NREL's cells use HWCVD instead of plasma enhanced CVD to eliminate the potential ion damage to the high-quality c-Si wafer surface during deposition.…”