Controllable Formation of Ordered Vacancy Compound for High Efficiency Solution Processed Cu(In,Ga)Se₂ Solar Cells

Abstract

Solution processing of Cu(In,Ga)Se2 (CIGS) absorber makes it cost‐competitive in the photovoltaic market. It is reported that copper‐poor ordered vacancy compound (OVC) is crucial for high performance CIGS solar cells. However, in solution process method, controllable formation of OVC is unavailable and limited research has been carried out. In this work, the controllable formation of the OVC phase on the CIGS surface is successful by controlling the selenization temperature and intentional variation of Cu/(In+Ga) stoichiometry in precursors for top layers and bulk layers deposition. The effects of OVC contents on the device performance are investigated. The CIGS thin film with OVC phase exhibits a lower valence band position. Meanwhile, the CIGS devices with optimized OVC content show decreased interface defects density and better carrier collection ability. The above advantages translate into a champion PCE of 16.39% for CIGS device with OVC phase, which is the champion performance among non‐hydrazine solution‐processed CIGS solar cells. The results demonstrate that the controllable formation of OVC phase approach should make a significant contribution to the efficiency promoting of solution processed CIGS solar cells.

Enabling fine-grain free 2-micron thick CISe/CIGSe film fabrication via a non-hydrazine based solution processing route

“…The application of a gallium gradient, surface treatments, OVC near interface, Ag addition, and heavy alkali treatments are known to improve the performance of CIGSe films. As most of the aforementioned strategies have already been demonstrated for amine-thiol based CIGSe films, [8][9][10][11] our amine-thiol based uniform CIGSe film has more potential to improve its performance through these modifications.…”

“…7 Currently, the aminethiol solvent system has produced the highest efficiency nonhydrazine based solution processed device with an active area efficiency of 16.4% for CIGSe thin films. 8 This solution system has also successfully demonstrated gallium grading, 9 silver addition, 10 and surface treatments like sulfurization 11 and creating ordered vacancy compounds 8 for improvement of uniform CIGSe thin films through solution processing routes. Other than aminethiol, routes which have produced CIGSe devices with efficiency around 14-15% involve CuInGaS 2 (CIGS) nanoparticles, 12 alcohol based route, 13 and DMF-thiourea based route.…”

Defect Control for High‐Efficiency Cu2ZnSn(S,Se)4 Solar Cells by Atomic Layer Deposition of Al2O3 on Precursor Film

“…[10] As a substitute in the large-scale thin-film production technology of Cu(In,Ga)Se 2 (CIGS), kesterite thin-film solar cells including Cu 2 ZnSn(S,Se) 4 (CZTSSe) have the same advantages and device structures. [11][12][13][14] The current power conversion efficiency (PCE) of CZTSSe thin-film solar cells has reached 12.6%. [15] However, it is much lower than both its detailed balance limit efficiency and the efficiency of the corresponding CIGS devices, [16,17] which is mainly due to a large open-circuit voltage deficit.…”

Characterization of MOCVD-Prepared CIS Solar Cells

“…An ordered vacancy complex (OVC) is generally used to describe the Cu-deficient phase of CIS. Furthermore, the presence of an OVC generally indicates buried-junction characteristics [25][26][27].…”