Advanced Characterisation of Chalcopyrite Electrodeposited Semiconductor for Enhanced Devices - ACCESSED

Coordinating Institution: Université du Luxembourg
Contracting Partner(s): CRP Gabriel Lippmann
From: 01/01/2009
To: 31/12/2011
Budget: 395,000.00€
Contact(s): Dale Phillip

Progress Summary 2009

The ACCESSED project follows the question how to improve electrodeposited and annealed (EDA) chalcopyrite semiconductors in order to reach the quality of physical vapour deposited (PVD) material. Annealing electrodeposited pre-cursors offers a low cost route to producing semiconductors, and can be used to make the chalcopyrite absorber layer copper indium gallium diselenide (Cu(In,Ga)Se2) in thin film solar cells. However, at present EDA has worse performance than other fabrication routes such as PVD.

The best PVD Cu(In,Ga)Se2 solar cells have an efficiency of 20 %, whilst EDA Cu(In,Ga)Se2 solar cells are stuck at 13.8 %. Therefore to investigate the underlying differences between the two approaches chemical, structural, and interfacial comparisons of electrodeposited Cu(In,Ga)Se2 will be made alongside reference PVD material. New methods will then be found to increase the similarity of the Cu(In,Ga)Se2 material to the PVD material and thus improve overall efficiency of thin film devices made from EDA absorber layers. The first year was concentrated on the synthesis of EDA-CuInSe2 material and PVD Cu(In,Ga)Se2 material for reference purpose. For the EDA route a stack of two reactive phases (In2Se3 and Cu or copper selenide) was electrodeposited.

Thermodynamic considerations promise a better recrystallization of such a stack in comparison to a layer, where all three elements are co-electrodeposited. The electrodeposition of indium selenide has been a critical step, since common stationary electrodeposition tends to be a slow process and to form dendrites on the surface. The electrodeposition set up was optimized to allow a controlled mass flow and the deposition bath was optimized to prevent the formation of indium hydroxide. In the end smooth and uniform layers of stoichiometric In2Se3 could be obtained.

The annealing of the electrodeposited In2Se3/Cu and In2Se3/CuxSey stacks led to single phase CuInSe2 material, which could be shown by X-ray diffractommetry (XRD). For the latter stack a case of complete recrystallization could be observed leading to crystal sizes up to 2μm which is a prerequisite for high performing solar cells. For PVD Cu(In,Ga)Se2 material the deposition conditions could be optimized so that solar cells with an efficiency of 14.7% could be achieved. Future work will be aiming on improving the photoactivity of the electrodeposited layers and the inclusion of Ga. This improved material will then be compared to PVD one with respect to chemical, structural and interfacial differences.

Refereed Scientific Publications: ---
Other Publications:
  • J. Fischer, P.J. Dale, and S. Siebentritt, ECS Transactions, 25, (2010) – to be published
  • P.J. Dale and L.M.Peter, Book chapter in, Advances in electrochemical science and engineering series – to be published
Project Website:

Figure 1: Lux-Tube Furnace

Figure 2: Pre-cursor stack consisting of electrodeposited In2Se3 on Mo-substrate covered by a layer of Cu2-xSe. Annealing this stacks leads to a copper indium diselenide semiconductor for thin film solar cells.