In₂O₃:H-Based Hole-Transport-Layer-Free Tin/Lead Perovskite Solar Cells for Efficient Four-Terminal All-Perovskite Tandem Solar Cells

Abstract

Narrow-band gap (NBG) Sn−Pb perovskites with band gaps of ∼1.2 eV, which correspond to a broad photon absorption range up to ∼1033 nm, are highly promising candidates for bottom solar cells in all-perovskite tandem photovoltaics. To exploit their potential, avoiding optical losses in the top layer stacks of the tandem configuration is essential. This study addresses this challenge in two ways (1) removing the hole-transport layer (HTL) and (2) implementing highly transparent hydrogen-doped indium oxide In 2 O 3 :H (IO:H) electrodes instead of the commonly used indium tin oxide (ITO). Removing HTL reduces parasitic absorption loss in shorter wavelengths without compromising the photovoltaic performance. IO:H, with an ultra-low near-infrared optical loss and a high charge carrier mobility, results in a remarkable increase in the photocurrent of the semitransparent top and (HTL-free) NBG bottom perovskite solar cells when substituted for ITO. As a result, an IO:H-based four-terminal all-perovskite tandem solar cell (4T all-PTSCs) with a power conversion efficiency (PCE) as high as 24.8% is demonstrated, outperforming ITObased 4T all-PTSCs with PCE up to 23.3%.

Monolithic All‐Perovskite Tandem Solar Cells with Minimized Optical and Energetic Losses

“…Hydrogenated indium oxide (IOH) has been used as a transparent contact due to its high transparency (optical constants in Figure S14, Supporting Information) which makes it ideal for use in multijunction devices limited by the free‐carrier absorption of ITO. [ 38,39 ] Furthermore, as described before, the use of a 20 nm‐thick PEDOT:PSS layer can increase light absorption in the narrow‐bandgap solar cell. Figure 3c shows the absorption contributions in tandem cells using IOH instead of ITO and a thinner (20 nm‐thick) PEDOT:PSS layer.…”

The role of A-site composition in the photostability of tin–lead perovskite solar cells

“…However, it has been shown that under operating conditions, the interface between PEDOT:PSS and the perovskite presents signs of degradation. (23) Different approaches to minimize this issue include the removal of the HTL (23)(24)(25), or the use of other HTLs such as NiO x or PTAA. (26)(27)(28)(29) Another critical aspect of the device stability is the selection of the A-site cation, namely Cs, MA, and formamidinium (FA).…”

“…However, it has been shown that under operating conditions, the interface between PEDOT:PSS and the perovskite presents signs of degradation. 23 Different approaches to minimize this issue include the removal of the HTL 23–25 or the use of other HTLs such as NiO x or PTAA. 26–29…”

Scalable two-terminal all-perovskite tandem solar modules with a 19.1% efficiency

“…riggered by the advances of single-junction organic-inorganic metal halide perovskite solar cells (PSC) with a wide range of bandgaps 1-3 , perovskite-based tandem photovoltaics (PVs) have come into research focus in recent years [4][5][6][7] . The promise of any tandem PV technology lies in high power conversion efficiencies (PCEs), beyond the Shockley-Queisser limit of single-junction solar cells [8][9][10][11] . Along with perovskite/silicon [12][13][14] and perovskite/ Cu(In,Ga)Se 2 [15][16][17] tandem photovoltaics, two-terminal all-perovskite tandem solar cells (2TPT-SCs) have raised great interest in recent years, combining a wide bandgap (WBG) perovskite top subcell (E G-top ≈ 1.6-1.8 eV) and a narrow-bandgap (NBG) perovskite bottom subcell (E G-bottom < 1.3 eV) [4][5][6][7][18][19][20][21][22][23] .…”