Efficiency Enhancement of CIGS Solar Cells via Recombination Passivation

Abstract

Cu­(In,Ga)­Se2 (CIGS) solar cells attract intense interest both in research and industry fields due to their high power conversion efficiencies, low costs, and high stabilities. The power conversion efficiency of a CIGS solar cell is limited by the deep level defects distributed on the surface and in the bulk of the CIGS solar cells. In this work, we elucidate that the deep level defects are significantly suppressed during the CdS buffer layer deposition process via a chemical bath deposition (CBD) method. The X-ray photoelectron spectroscopy results show the incorporation of cadmium (Cd) into CIGS during the CdS deposition process, which is the main reason for the reduced deep level nonradiative recombination defects. Raman spectroscopy and secondary ion mass spectroscopy further reveal the reduction of nonradiative recombination deep level defects due to Cd incorporation. Besides, the high-resistivity i-ZnO layer provides field-effect passivation, leading to the enhancement of the power conversion efficiency from 11.0 to 12.1%. By a combination of the incorporation of Cd, i-ZnO passivation, and optimization of the band gap of CIGS, the champion power conversion efficiency of the CIGS solar cell is as high as 15.5% without an antireflective layer and alkali metal postdeposition treatment. Our results provide insights into the effect of the CdS buffer layer, CBD method, and high-resistivity i-ZnO layer on the performance of CIGS solar cells, which is quite helpful to further improve the power conversion efficiency of CIGS solar cells.

9.3% Efficient Flexible Cu2ZnSn(S,Se)4 Solar Cells with High‐Quality Interfaces via Ultrathin CdS and Zn0.8Sn0.2O Buffer Layers

“…It is well known that the CdS film has been one of the most efficient buffer layers for CZTSSe solar cells, due to the favorable effect of the CBD preparation process and the efficient passivation of surface defects through the diffusion of Cd 2þ . [33,34] Therefore, a 10 nm CdS film is required as an interface passivation layer to protect the surface of the CZTSSe layer and passivate the heterojunction interface defects. Moreover, it effectively reduces the content of Cd compared with the standard device, which is of great significance to protect the environment.…”

Thermal Effect on the Electronic Properties of ZnO/CdS/CIGSeS Solar Cell at/near the Heterojunction Interfaces

“…For the proposed mechanism regarding the carrier separation in the CIGS-based solar cells, the ODC domains in the CIGS surface region have been linked to internal homojunctions, which can promote the efficient separation of charge carriers and avoid carrier recombination. The formation of an inversion layer occurs by a method of Cd from CdS into copper vacancies of ODC , during a chemical bath process; the donor defect Cd Cu contributes free electrons to the ODC surface resulting in an n-type inversion layer. Furthermore, the surface sulfidation increases the contribution of the valence band to enlarge the inversion effect, thereby improving the V oc .…”

Front Transparent Passivation of CIGS-Based Solar Cells via AZO

“…The Mo hole transport layer is deposited at RT via a one−stage direct−current (DC) magnetron sputtering method with a DC voltage and current of 386 V and 0.65 A, respectively. The CIGS absorbing layer with a thickness of ~2.3 μm ( Figure 1 i) is grown via a three−stage co−evaporation method in a home−made five−source co−evaporation system, as has been described in our published paper [ 8 ]. The CdS buffer layer is synthesized via a chemical bath deposition (CBD) method at 70 °C.…”

“…The consensus on V oc,loss has been reached, predominantly ascribing it to the non−radiative recombination induced by the bulk and interface defects [ 7 ]. Many strategies involving the doping of isoelectronic elements such as Ag and Cd into the CIGS absorbing layer [ 6 , 8 ], and passivation of interface defects [ 9 ], have been exploited to passivate the unpopular non−radiative recombination defects in CIGS solar cells. These strategies mainly focus on the passivation of defects located in the CIGS and buffer layers and their interface, which is extremely insufficient because many layers and interfaces exist in the CIGS solar cell having a typical configuration of substrate/Mo/CIGS/buffer layer/high−resistive layer (HRT)/transparent conductive oxide (TCO)/metal electrode/anti−reflective layer [ 8 , 9 , 10 ].…”