DOI: 10.1002/ijch.201400191 Development of Selective Electroless-Deposited Electrode in Heterojunction with Intrinsic Thin-Layer Solar Cell Areum Kim, Hyunjin Park, Eunmi Choi, Yinhua Cui, Seon Jea Lee, and Sung Gyu Pyo* [a] 1. Introduction Among silicon solar cells, which comprise 80% of the global solar cell market, the HIT solar cell, developed by SANYO, generally consists of laminated amorphous and monocrystalline silicon. [1–3] Its structure includes a very thin amorphous layer (p-type, n +-type, and i-type), gen- erated using the plasma chemical vapor deposition (CVD) method on the front and rear sides of n-type mon- ocrystalline silicon and indium tin oxide (ITO), and an Ag electrode on each side (Figure 1a). In contrast to monocrystalline silicon solar cells, the manufacturing tem- peratures for HIT solar cells – 200 8C or below – allow them to be very thin. The HIT solar cell also exhibits de- creased recombination at the interface and improved Voc due to the insertion of a very thin amorphous layer. The cell can also generate electricity from light reflected by its rear side. [4–7] However, the price of Ag, which usually comprises the major electrode in HIT cells, has increased continuously. Ag paste, due to the glass frits it contains, is more highly resistive than Ag itself, whose resistivity is 1.60 mW cm. Many studies have substituted a different electrode in order to achieve high efficiency. [8–10] In particular, Cu became popular as a new material for constructing elec- trodes because it has a resistivity of 1.70 mW cm. [11–16] The process of electroless plating can save both time and money because it is based on chemical reduction. Many researchers have conducted electroless plating of Cu as a main electrode, however it is rare to apply this method in HIT solar cells. [17–19] Lee et al. applied electroless- plated Cu electrodes in HIT cells, but cell performance was not measured. [20] Cu is oxidized more easily than Ag. When oxygen diffuses onto the surface of Cu, Cu oxide is formed and interrupts the electric flow. [21–22] Therefore, a certain process is required for surface treatment or the removal of the oxide layer to preserve the Cu, which comprises the main portion of the electrode. In this study, Cu was selected as a main electrode to re- alize an inexpensive HIT solar cell with high per- formance, and a simple process of electroless deposition was conducted. After applying various electroless deposi- tion solutions such as Sn and Ni to prevent the oxidation of the Cu surface, the characteristics of the capping layer were analyzed. Next, to reduce the contact resistance of the interface, the interface characteristics were evaluated after annealing. Finally, in order to compare our cell with existing commercial Ag HIT solar cells, we examined the possibility of commercializing the electrode fabricated using the proposed approach by determining its efficiency and FF using a solar simulator. Abstract : In this paper, we describe selective deposition of a major electrode and a protection electrode in a heterojunc- tion with intrinsic thin-layer (HIT) type solar cell. Sn and Ni were used for the protection electrode to prevent the oxida- tion of Cu, which was used for the main electrode. SEM and TEM were used to analyze the microstructural evolution and changes in the interface as a result of each electroless depo- sition. Finally, the performance of our solar cell created via electroless deposition was evaluated. We determined the photovoltaic conversion efficiency (PCE) to be 16.4%, the fill factor (FF) to be 72.2 %, the open circuit voltage (Voc) to be 681 mV, and the short circuit current ( Jsc) to be 33.0 mA/cm 2 . These output values match the performance of an Ag screen-printed solar cell and demonstrate the pos- sibility of commercializing an inexpensive HIT solar cell with high efficiency. Keywords: electrochemistry · electroless deposition · heterojunction with intrinsic thin-layer (HIT) solar cells · microstructural evolution · Sn [a] A. Kim, H. Park, E. Choi, Y. Cui, S. J. Lee, S. G. Pyo School of Integrative Engineering Chung-Ang University 221, Heukseok-Dong Dongjak-Gu, Seoul, 156-756 (Korea) Tel: (+ 82) 2-820-5781 Fax: (+ 82) 2-814-2651 e-mail: sgpyo@cau.ac.kr Isr. J. Chem. 2015, 55, 1070 – 1074 # 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1070 Full Paper