Figure 2.

Ref. [101] PL spectra of (a) the light absorption was observed when inserting ETL but no absorption after injecting Spiro-OMeTAD as HTL as the expected result. When CuIn0.75Ga0.25S₂ was injected as HTL, the high intensity was observed so that the light goes beyond perovskite to generate electrons, and holes may disturb the function of HTL [101]. Reprinted with permission from Solar RRL © 2020 WILEY–VCH Verlag GmbH & Co. KGaA, Weinheim, Germany. (b) PL spectra of pristine perovskite and two precursor solvents, ZnAc₂ and NH₄Ac, were added to the perovskite. This illustrates that the higher the perovskite intensity, the better the efficiency [65]. Reprinted with permission from the Journal of Alloys and Compounds © 2019 Elsevier B.V.