H₂ plasma treatment at the p/i interface of a hydrogenated amorphous Si absorption layer for high‐performance Si thin film solar cells

Abstract

Plasma treatment (PT) of the buffer layer for highly H2‐diluted hydrogenated amorphous silicon (a‐Si:H) absorption layers is proposed as a technique to improve efficiency and mitigate light‐induced degradation (LID) in a‐Si:H thin film solar modules. The method was verified for a‐Si:H single‐junction and a‐Si:H/microcrystalline silicon (µc‐Si:H) tandem modules with a size of 200 × 200 mm2 (aperture area of 382.5 cm2) under long‐term light exposure. H2 PT at the p/i interface was found to eliminate non‐radiative recombination centers in the buffer layer, and plasma‐enhanced chemical vapor deposition at low radio‐frequency power was found to suppress the generation of defects during the growth of a‐Si:H absorption layers on the treated buffer layers. With optimized H2 PT of the a‐Si:H single‐junction module, the stabilized short circuit current and fill factor increased, and the stabilized open circuit voltage moves beyond its initial value. The results demonstrate 7.7% stabilized efficiency and 10.5% LID for the a‐Si:H single‐junction module and 10.82% stabilized efficiency and 7.76% LID for the a‐Si:H/µc‐Si:H tandem module. Thus, the growth of an a‐Si:H absorption layer on a H2 PT buffer layer can be considered as a practical method for producing high‐performance Si thin film modules. Copyright © 2012 John Wiley & Sons, Ltd.

Record amorphous silicon single-junction photovoltaic module with 9.1% stabilized conversion efficiency on 1.43 m2

“…The H 2 plasma treatment was carried out in the same PECVD reactor just after the deposition of the buffer layer. Similar H 2 plasma treatments of a-Si:H layers in order to improve cell performance and reduce LID have been reported by others [27]. The insertion of this buffer layer had no significant impact on the initial performance.…”

CuOx/a‐Si:H heterojunction thin‐film solar cell with an n‐type µc‐Si:H depletion‐assisting layer

“…The best performance parameters are summarized in Table II for (a) an a-Si:H solar cell with a 4-nm n-μc-Si:H layer, (b) an CuO x (50-nm-thick)/i-a-Si:H HSC without the DAL, and (c) an n-CuO x (50-nm-thick)/i-a-Si:H HSC with the DAL. Cell (a) showed significantly low V OC and η of 0.5 V and 2.77%, respectively, compared with the values of~0.9 V and~9% for general p-i-n a-Si:H single-junction solar cells [20]. This indicates that the 4-nm n-μc-Si:H layer was too thin to serve as an independent n-type layer, and thus, we could use it as a DAL for the n-CuO x /i-a-Si:H HSC.…”

Highly improved passivation of c-Si surfaces using a gradient i a-Si:H layer

“…In SHJ solar cells, a key factor for high efficiency is suppressing carrier recombination at the a-Si:H/c-Si interface since it affects the minority carrier lifetime and open circuit voltage (Voc). To reduce recombination rates, the c-Si surface can be passivated by thermal annealing treatments, 5 H 2 plasma treatment, 6,7 or thin film deposition. 8 Among the various treatments, surface passivation using intrinsic a-Si:H (i a-Si:H) thin films has been very effective due to passivation of Si dangling bonds at the i a-Si:H/c-Si interface.…”