Performance improvement of CdS/Cu(In,Ga)Se₂solar cells after rapid thermal annealing

Abstract

In this paper, we investigated the effect of rapid thermal annealing (RTA) on solar cell performance. An opto-electric conversion efficiency of 11.75% (Voc = 0.64 V, Jsc = 25.88 mA/cm2, FF=72.08%) was obtained under AM 1.5G when the cell was annealed at 300 °C for 30 s. The annealed solar cell showed an average absolute efficiency 1.5% higher than that of the as-deposited one. For the microstructure analysis and the physical phase confirmation, X-ray diffraction (XRD), Raman spectra, front surface reflection (FSR), internal quantum efficiency (IQE), and X-ray photoelectron spectroscopy (XPS) were respectively applied to distinguish the causes inducing the efficiency variation. All experimental results implied that the RTA eliminated recombination centers at the p–n junction, reduced the surface optical losses, enhanced the blue response of the CdS buffer layer, and improved the ohmic contact between Mo and Cu(In, Ga)Se2 (CIGS) layers. This leaded to the improved performance of CIGS solar cell.

Characterization of (CIGS)/(CdS) Hetrojunction for Solar Cell

“…Typically the most common material used for the back contact is molybdenum (Mo) (especially for soda lime glass substrates) and forms a non-blocking contact with CIGS, also other materials like tungsten (W), tantalum (Ta), manganese (Mn), titanium (Ti), have been used as back contact (Ramanathan et al,1998;Benmir and Aida, 2013). Variety of deposition techniques used to fabricate CIGS/CdS solar cells such as three stag process method (Ramanathan et al, 1998), thermal evaporation (Benmir and Aida, 2013), vacuum co-evaporation (Singh and Patra, 2010;Gloeckler, 2005), sputtering/selenization, (Urbaniak et al, 2016;Kumari and Verma, 2014), co-sputtering method (Li et al, 2012), i PLD method (Park et al, 2014), chemical bath deposition with efficiencies exceeding 18% (Dong-Sheng et al, 2013;Dhas et al, 2017), electrodeposition (Zhao et al, 2016;Saji et al, 2011), Physical vapor deposition (PVD) (Cojocaru-Miredin et al, 2011) and spin-coating method (Motoyoshi et al, 2010).Cadmium Sulfide (CdS) thin film plays important n-type absorber material based on CIGS and CdTe thin films (Nakada and Mizutani, 2002;Ramasamy et al, 2017). The CdS is still mostly used as a buffer layer or window layer for CIGS cells and other many p-types absorbers layers like Cu 2 S, CdTe, InP because of CdS belongs to n-type semiconductor compounds with wide band gap (2.0-2.42) eV and this leads to fabricate cells with high-efficiency (Mollica, 2016;Mustafa et al, 2017).…”

Phase equilibrium of Cd 1– x Zn x S alloys studied by first-principles calculations and Monte Carlo simulations

“…[1][2][3] The former is a typical material for the buffer layer of the high-efficiency CuIn 1−x Ga x Se 2 thin film solar cells. [4] However, cadmium, a kind of heavy metal toxic element, can do harm to the environment and human health. To reduce the cadmium usage as well as to improve the optical and electronic properties of the buffer layer, one feasible way is to replace CdS by Cd 1−x Zn x S solid solution.…”

Synthesis, structure, optical, and electric properties of Ce-doped CuInTe 2 compound

“…I-III-VI 2 ternary compound with chalcopyrite structures have been extensively studied due to their applications in photovoltaic cells. [1][2][3][4][5] CuInSe 2 solid solution with Ga substitution for In, and S substitution for Se, commonly referred to as Cu(In,Ga)(Se,S) 2 (CIGS), [6,7] is a leading candidate material of solar cells because of its high photoelectric transformation efficiency of 20.3%. [8] Since Te also belongs to VI group, the tellurium-based semiconductor with a chalcopyrite structure is widely investigated for its potential application in solar cells.…”