Efficient All‐Perovskite Tandem Solar Cells with Low‐Optical‐Loss Carbazolyl Interconnecting Layers

Abstract

Combining wide‐bandgap (WBG) and narrow‐bandgap (NBG) perovskites with interconnecting layers (ICLs) to construct monolithic all‐perovskite tandem solar cell is an effective way to achieve high power conversion efficiency (PCE). However, optical losses from ICLs need to be further reduced to leverage the full potential of all‐perovskite tandem solar cells. Here, metal oxide nanocrystal layers anchored with carbazolyl hole‐selective‐molecules (CHs), which exhibit much lower optical loss, is employed to replace poly(3,4‐ethylenedioxythiophene) polystyrenesulfonate (PEDOT: PSS) as the hole transporting layers (HTLs) in lead‐tin (Pb‐Sn) perovskite sub‐cells and ICLs in all‐perovskite tandem solar cells. Optically transparent indium tin oxide nanocrystals (ITO NCs) layers are employed to enhance anchoring of CHs, while a mixture of two CHs is adopted to tune the surface energy‐levels of ITO NCs. The optimized mixed Pb‐Sn NBG perovskite solar cells demonstrate a high PCE of 23.2%, with a high short‐circuit current density (Jsc) of 33.5 mA cm‐2. A high PCE of 28.1% is further obtained in all‐perovskite tandem solar cells, with the highest Jsc of 16.7 mA cm‐2 to date. Encapsulated tandem solar cells maintain 90% of their reference point after 500 h of operation at the maximum power point (MPP) under 1‐Sun illumination.

Self‐assembled monolayers for perovskite solar cells

“…Panel (A) reproduced with permission from refs. 83, 129–134, 11a, respectively. Copyright 2022 Springer Nature, 2023 Wiley, 2023 Wiley, 2024 The Royal Society of Chemistry, 2023 Springer Nature, 2023 Springer Nature, 2023 Wiley, 2023 Wiley, respectively.…”

“…Recently, our group also published a study on achieving an NBG PVK efficiency of 23.2% and a high‐efficiency tandem cell of 28.1% using a combination of mixed SAMs (Me‐4PACz:MeO‐2PACz = 1:1) and ITO nanocrystals (ITO NCs) as the ICL. Furthermore, the encapsulated cells maintained 90% of their initial point after operating at the MPP for 500 h 11a …”

“…Here, we propose our own views and prospects. Firstly, from the energy level perspective, as shown in Figure 8G, the presence of Sn in NBG PVK leads to a shallower HOMO energy level (approximately −5.27 eV), 11b which results in PEDOT:PSS being commonly used as the HTL layer in NBG PSCs, rather than PTAA or NiO x , which have superior stability and hole mobility. Moreover, commonly used SAMs tend to shift the surface WF of MOs toward a deeper value, which is more unfavorable for hole transfer.…”

“…In the development of these strategies, SAMs have emerged as a promising approach 9 . Notably, in the currently published literature, the highest power conversion efficiencies (PCE) for single‐junction mid‐bandgap PSCs (25.6%), 10 all‐PVK tandem solar cells (over 28%) 11 and silicon/PVK tandem solar cells (32.5%) 12 have all been achieved through the incorporation of SAMs.…”