A carbazole-based self-assembled monolayer as the hole transport layer for efficient and stable Cs_0.25FA_0.75Sn_0.5Pb_0.5I₃solar cells

Abstract

An analysis is provided of MA-free Sn/Pb-perovskite solar cells fabricated using PEDOT:PSS, 2PACz, and Br-2PACz as the HTL. An efficiency of 19.51% has been reached by using Br-2PACz with improved device stability, thanks to suppressed recombination.

Recent progress in monolithic two-terminal perovskite-based triple-junction solar cells

“…Consequently, solar cells utilizing Br-2PACz demonstrated superior performance and stability compared to PEDOT:PSS and 2PACz. 106 In a later study they improved the wetting of the Sn-based perovskite on SAM by deposition of a carbazole alkylammonium iodide derivative (4CzNH 3 I) layer on top of Br-2PACz (Fig. 11).…”

Narrow Bandgap Metal Halide Perovskites for All-Perovskite Tandem Photovoltaics

“…Compared with the neat Pb PSCs, however, we find that the SAM-based mixed Sn−Pb PSCs do generally suffer from reduced batch-to-batch reproducibility. This problem has led to very few successful attempts made by a limited number of groups in the Sn-containing PSCs. − There are several reasons related to this, e.g., (i) unsuitable energy level alignment which will generate severe nonradiative carrier recombination, and (ii) poor coverage of the SAMs on the TCO substrate that will lead to the current leaking and/or detrimental side reactions between the perovskite and substrate. Most of the SAMs developed currently have HOMO levels around −5.6 to −5.9 eV, , which match the valence band maximum (VBM) of the neat Pb perovskite films but is much deeper than the VBM of most Sn-containing analogues, generally from −5.0 to −5.4 eV, ,,, as the energy level of the Sn 5s orbital is shallower than that of 6s of Pb .…”

Self-assembled monolayers as hole-transporting materials for inverted perovskite solar cells

“…In addition to Pb-based PSCs, Loi et al applied the Br-substituted carbazole SAM ([2-(3,6-dibromo-9 H -carbazol-9-yl)ethyl]phosphonic acid, Br-2PACz) and 2PACz in mixed tin/lead (Sn/Pb) PSCs to replace the normally-used PEDOT:PSS. 59 By comparing two liquid-phase deposition methods, they found that the ITO surface was fully covered via liquid-phase immersion while the spin-coating process did not give a dense SAM-HTL, with only a portion of SAM molecules attaching to the substrate (Fig. 3c).…”