Si‐Doped Cu(In,Ga)Se₂ Photovoltaic Devices with Energy Conversion Efficiencies Exceeding 16.5% without a Buffer Layer

Abstract

In this communication, novel and simplified structure Cu(In,Ga)Se2 (CIGS) solar cells, which nominally consist of only a CIGS photoabsorber layer sandwiched between back and front contact layers but yet demonstrate high photovoltaic efficiencies, are reported. To realize this accomplishment, Si‐doped CIGS films grown by the three‐stage coevaporation method, B‐doped ZnO transparent conductive oxide front contact layers deposited by chemical vapor deposition, and heat–light soaking treatments are used. Si‐doping of CIGS films is found to modify the film surfaces and grain boundary properties and also affect the alkali metal distribution profiles in CIGS films. These effects are expected to contribute to improvements in buffer‐free CIGS device performance. Heat–light soaking treatments, which are occasionally performed to improve conventional buffer‐based CIGS device performance, are found to be also effective in enhancing buffer‐free CIGS photovoltaic efficiencies. This result suggests that the mechanism behind the beneficial effects of heat–light soaking treatments originates from CIGS bulk issues and is independent of the buffer materials. Consequently, over 16.5% efficiencies, including an independently certified value, are demonstrated from completely buffer‐free CIGS photovoltaic devices.

Perovskite Tandem Solar Cells: From Fundamentals to Commercial Deployment

“…155 For example, the i-ZnO/ AZO layer applied in the CIGS bottom cell is proved to be an effective RL in the 2T TSC, making it possible to directly grow PSC top cell on CIGS bottom cell. 145 However, CIGS solar cells with high PCEs are usually fabricated via a vacuum method like sputtering 328 or co-evaporation, 329 which usually leads to large roughness for CIGS films and upper AZO layers. 330 The large roughness of AZO results in a difficulty in the subsequent fabrication of PSC which is usually deposited via a solution method and composed of several functional layers with thicknesses in the range of a few tens to hundreds of nanometers.…”

An over 18%-efficient completely buffer-free Cu(In,Ga)Se2 solar cell

“…4,16) We have investigated the potential of completely buffer-free CIGS solar cells and reported the effectiveness of the use of Si-doped CIGS films as the photoabsorber layer to enhance the efficiency. 17,18) In the current study, a photovoltaic efficiency of over 18%, a value approaching that of conventional buffer-based CIGS photovoltaic cells, is achieved and thus can serve as a benchmark for this type of buffer-free CIGS device.…”

“…Details of film growth and device fabrication processes can be found in our previous reports. 17,18) Heat-light soaking (HLS) treatments (90 °C, 0.4-1 sun illumination, N 2 atmosphere or in vacuum) were performed on completed CIGS devices to activate metastable acceptors in CIGS. In this study, two HLS apparatuses were employed.…”

Advances in solar photovoltaics: Technology review and patent trends

“…Its cell efficiency record is 22.1%. On the other hand, CIGS cell technology with efficiency record of 22.9% can be manufactured using screen-printing, spray coating, spin coating, MOCVD, or electron beam deposition [31,32].…”