A Comprehensive Study of One-Step Selenization Process for Cu(In1−x Ga x )Se2 Thin Film Solar Cells

Abstract

In this work, aiming at developing a rapid and environmental-friendly process for fabricating CuIn1−xGaxSe2 (CIGS) solar cells, we demonstrated the one-step selenization process by using selenium vapor as the atmospheric gas instead of the commonly used H2Se gas. The photoluminescence (PL) characteristics indicate that there exists an optimal location with superior crystalline quality in the CIGS thin films obtained by one-step selenization. The energy dispersive spectroscopy (EDS) reveals that the Ga lateral distribution in the one-step selenized CIGS thin film is intimately correlated to the blue-shifted PL spectra. The surface morphologies examined by scanning electron microscope (SEM) further suggested that voids and binary phase commonly existing in CIGS films could be successfully eliminated by the present one-step selenization process. The agglomeration phenomenon attributable to the formation of MoSe2 layer was also observed. Due to the significant microstructural improvement, the current–voltage (J-V) characteristics and external quantum efficiency (EQE) of the devices made of the present CIGS films have exhibited the remarkable carrier transportation characteristics and photon utilization at the optimal location, resulting in a high conversion efficiency of 11.28%. Correlations between the defect states and device performance of the one-step selenized CIGS thin film were convincingly delineated by femtosecond pump-probe spectroscopy.

High‐temperature fabrication of Ag(In,Ga)Se2 thin films for applications in solar cells

“…Photovoltaic applications of AIGS thin films as the light‐absorbing layer of solar cells have been reported in our previous work and that of other groups . Among the approaches for fabricating high efficiency CIGS solar cell, such as selenization of the CuInGa precursor , single stage co‐evaporation , and three‐stage co‐evaporation , the three‐stage method is regarded as the most effective approach . In our previous studies, we deposited AIGS films by a modified three‐stage method using molecular beam epitaxy, and we achieved an efficiency of 10.7%.…”

Review of CIGS-based solar cells manufacturing by structural engineering

“…Some theoretical and experimental studies have been conducted to obtain high efficient CIGS-based solar cells. Among them, structural modifications of crystalline and electronic structures to tune its functionalities are considered to be a general route to enhance the CIGS-based solar cell efficiency (Asaduzzaman et al, 2016;Chen et al, 2017b;Chiril� a et al, 2013;Han et al, 2012;Ishizuka et al, 2011;Liao et al, 2013;Liu et al, 2011;Malitckaya et al, 2017;Puyvelde et al, 2014;Salom� e et al, 2013;Su et al, 2011;Sun et al, 2017).…”

“…The effects of impurity or doping are also briefly discussed including direct doping by the addition of impurities to the CIGS layer directly during or after the coating process and indirect doping, which is facilitated by the diffusion of related materials from the substrates and/or buffer layers (Asaduzzaman et al, 2016;Chiril� a et al, 2013;Malitckaya et al, 2017;Puyvelde et al, 2014;Salom� e et al, 2013;Shirakata, 2017;Sun et al, 2017). Moreover, selenization and annealing processes, which are considered to be important for tuning the electronic structure, are explained (Chen et al, 2017b;Ramanujam and Singh, 2017). Thus, the design of the CIGS layer morphology, which is used to control the reflection behavior, is discussed (Cai and Qi, 2015;Han et al, 2012;Ishizuka et al, 2011;Liao et al, 2013;Liu et al, 2011;Shirakata, 2017;Su et al, 2011).…”

Femtosecond Laser Fabrication of Micro and Nano-Structures on CIGS/ITO Bilayer Films for Thin-Film Solar Cells

“…Currently, most investigations focus on improving the photoelectric conversion efficiency of the CIGS solar cells by adjusting the material composition or optimizing thin-film preparation technology [ 6 , 7 , 8 , 9 ]. Different fabrication methods (e.g., co-evaporation, continuous evaporation, sputtering, vacuum evaporation, and spray pyrolysis [ 10 , 11 , 12 , 13 , 14 ]) can modify the elemental composition of the films, thus affecting surface particle size and absorptivity. In addition, heat treatment in different atmospheres can alter the surface morphology of films so that their bandwidth structure and photoelectric properties can be adjusted [ 2 , 15 ].…”