Effects of CuAlO2 on the heterojunction interface and performance of Cu2ZnSn(S,Se)4 thin-film solar cells

Delafossite CuAlO2 Modification‐Induced Synergistic Passivation Effects for Heterojunction Interface and Absorber toward Efficient Kesterite Solar Cells

“…Compared to SA‐0, more compact and continuous surface morphology with larger grain is observed for SA‐110 and SA‐150, which can be elucidated as below. In the previous report, [ 45 ] it was explained qualitatively for the Cu–Se liquid‐phase‐assisted grain growth via citing the viewpoint of Kim et al [ 51 ] In this work, two additional experimental evidences are provided expect for the probably aforementioned explanation. As listed in Table 1 and Table 2 , after CAO modification, Na concentration (derived from SLG) at absorber surface (and HEI) witnessed an appreciable increase from SA‐0 to SA‐110 and SA‐150 via energy‐dispersive X‐Ray spectroscopy (EDS) and X‐Ray photoelectron spectroscopy (XPS) characterizations, which improves the absorber surface chemisorption of Se molecules.…”

“…In other words, Fermi level ( E F ) rises for the buffer layer. Meanwhile, considering the result of the surface conduction type‐converted absorber after CAO modification revealed in the previous work, [ 45 ] that is, E F of the CAO‐modified absorber surface also rises. Thus, it can be known that the E F difference between absorber and buffer layer becomes smaller with the passivation effect of CAO, which is beneficial for the formation of the smaller positive conduction band offset and higher HEI quality accordingly.…”

“…One is the validating HOFP effect aiming at HEI induced by CAO that has been revealed and discussed in the previous work. [ 45 ] The other is the depressed carrier recombination within HEI profited from the upgraded CPE and the improved absorber crystalline quality. This is evident from the decreased A and increased R Sh values presented in Table 4, too.…”

“…Finally, we achieved a CAO modification CZTSSe solar cell exceeding 10% PCE, which outperforms the prior reports. [ 45,47 ] Expectantly, we believe that our findings will shed light on how to simultaneously achieve high‐quality HEIs and absorbers with effectively depressed carrier recombination in kesterite solar cells field. To this end, through cross direction, combination of kesterite and delafossite is an alternative strategy with promising perspectives.…”

“…Recently, we have proposed a novel HEI field passivation method to inhibit carrier recombination and subsequently improve interface quality by applying CAO to HEI. [ 45 ] To be specific, HEI elements interdiffusion between Cu from the absorber and Al from CAO takes place among the selenization process of the absorber and then, inducing the expected electrical property inversion of the absorber shallow bulk from p‐ to n‐type and constructing HOFP. Despite the study demonstrating the benefits of CAO applied in HEI, the impact of these upon absorber deep bulk and buffer layer CdS hasn't yet been investigated to date.…”