Current photovoltaic trends shows that both improved efficiency and lowered cost can be obtained by heterojunction solar cell technology [1]. Silicon heterojunction solar cells consist of crystalline silicon (c-Si) wafers with typically 3-15 nm thick amorphous silicon layers deposited on both sides to form electrically passivated contacts. A hydrogenated i/p layer stack forms the emitter at the front side and a hydrogenated i/n layer stack forms the back-surface field. The use of such layers in heterojunction cells has many advantages such as low process temperatures, low cost, large area deposition and high cell efficiencies. Such a device structure has be pioneered by Sanyo [2] starting in the early 1990s increasing efficiency steadily to currently 24.7% [3] and 26.6% [4] with a double-sided heterojunction and an IBC-SHJ cell, respectively. The Si heterojunction solar cell structure fabricated in our laboratories is given below and has a 20.5% efficiency.

Figure 1. The Si heterojunction solar cell structure fabricated in NÖHÜNAM. Comparison of the Si heterojunction solar cell technology and the efficiency values of standard Si based solar cells according to the data obtained from NREL [1].

The following studies are carried out in our laboratory on Si heterojunction solar cells:

• Improved efficiency with the development of the heterojunction solar cell process
• Tandem solar cells (Perovskite, etc.) where Si heterojunction solar cell is a sub cell
• New materials as TCO
• The use of graphene as a TCO in heterojunction solar cells
• Nano surface patterning

Referances:

[1] DE WOLF S., DESCOEUDRES A., HOLMAN Z. C., BALLIF C., “High-efficiency silicon heterojunction solar cells: A review”, Green, 2(1), 7-24, 2012.

[2] LIU, Y., SUN, Y., LIU, W., YAO, J., “Novel high-efficiency crystalline-silicon-based compound heterojunction solar cells: HCT (heterojunction with compound thin-layer)”, Physical Chemistry Chemical Physics, 16 (29), 15400-15410, 2014.

[3] PATEL, K., TYAGI, P. K., “Technological advances in a-Si: H/c-Si Heterojunction solar cells”. International Journal of Renewable Energy Research (IJRER), 4 (2), 528-538, 2014.

[4] TAGUCHI, M., YANO, A., TOHODA, S., MATSUYAMA, K., NAKAMURA, Y., NISHIWAKI, T., FUJİTA, K., MARUYAMA, E., “24.7% record efficiency HIT solar cell on thin silicon wafer”. IEEE Journal of Photovoltaics, 4(1), 96-99, 2014.

[5] TSUNOMURA, Y., YOSHIMINE, Y., TAGUCHI, M., BABA, T., KINOSHITA, T., KANNO, H., SAKATA, H., MARUYAMA, E., TAKANA, M., “Twenty-two percent efficiency HIT solar cell”. Solar Energy Materials and Solar Cells, 93(6), 670-673, 2009.

[6] MAKOTO, T., MIKIO, T., TAKAO, M., TORU, S., SHINYA, T., SHOICHI, N., HIROSGI, H., YUKINORI, K., “Development of New a-Si/c-Si Heterojunction Solar Cells: ACJ-HIT (Artificially Constructed Junction-Heterojunction with Intrinsic Thin-Layer)”. Japanese Journal of Applied Physics, 31(11R), 3518 –3522, 1992.

[7] http://www.kaneka.co.jp/en/service/news/nr201708252/, (erişim tarihi 05.02.2019).

Researchers:   Assist. Prof. Dr.  Ayşe SEYHAN

                        Res. Assist. Elif DAMGACI

                        Emre KARTAL