Zr‐Doped Indium Oxide (IZRO) Transparent Electrodes for Perovskite‐Based Tandem Solar Cells

Abstract

Parasitic absorption in transparent electrodes is one of the main roadblocks to enable power conversion efficiencies (PCEs) for perovskite-based tandem solar cells beyond 30%. To reduce such losses and maximize light coupling, the broadband transparency of such electrodes should be improved, especially at the front of the device. Here, we show the excellent properties of Zr-doped indium oxide (IZRO) transparent electrodes for such applications, with improved near-infrared (NIR) response, compared to conventional In-doped tin oxide (ITO) electrodes. Optimized IZRO films feature a very high electron mobility (up to ~77 cm 2 /V•s), enabling highly infrared transparent films with very low sheet resistance (~18 for annealed 100 nm films). For devices, this translates in a parasitic absorption of only ~5% for IZRO within the solar spectrum (250-2500 nm range), to be compared with ~10% for commercial ITO. Fundamentally, we find that the high conductivity of annealed IZRO films is directly linked to promoted crystallinity of the indium oxide (In2O3) films due to Zr-doping. Overall, on four-terminal perovskite/silicon tandem device level, we obtained an absolute 3.5

2D/3D Heterostructure for Semitransparent Perovskite Solar Cells with Engineered Bandgap Enables Efficiencies Exceeding 25% in Four‐Terminal Tandems with Silicon and CIGS

“…[ 56,57,67 ] This is feasible, for example, by employing a p‐i‐n structure to eliminate thick spiro‐MeOTAD, [ 53,58,107 ] and more importantly by replacing the bottom and top ITO with less absorbing TCOs (which also possess a more suitable refractive index) such as indium zinc oxide (IZO), zirconium‐doped indium oxide (IZRO), or hydrogen‐doped indium oxide (IO:H). [ 14,34,49 ] Such improvements will further increase the overall PCE of 4T perovskite‐based tandem solar cells toward 30% in the near future and are focus of our current work.…”

“…To date, the most efficient perovskite‐based tandem solar cells have been realized using PSCs on top of low‐bandgap c‐Si [ 6,18,21,23,25,34–42,43 ] or thin‐film CIGS ( E g ≈ 1.0–1.2 eV) [ 24,44–49 ] solar cells. [ 4,19,20,50 ] Record PCEs of up to 29.1% (perovskite/c‐Si, 2T), [ 6 ] 27.7% (perovskite/c‐Si, 4T), [ 43,51 ] 23.3% (perovskite/CIGS, 2T), [ 48 ] and 25.9% (perovskite/CIGS, 4T) [ 45 ] have been reported for the different architectures and configurations.…”

Triarylphosphine Oxide as Cathode Interfacial Material for Inverted Perovskite Solar Cells

“…In order to demonstrate the potential application of DPO CIM in high‐performance device architectures such as perovskite‐based tandem solar cells, we fabricated semitransparent PSCs by replacing the evaporated metal electrode with a sputter‐deposited ITO as sketched in Figure a. In such devices, the ZnO‐np layer acts as a protection layer to sputter damage of the soft, underlying layers . Notably, inserting DPO between these ZnO‐np layers and the ITO transparent electrodes enabled an absolute 1.3 mA cm −2 current gain (Figure b), which is also confirmed by EQE measurements (Figure c).…”

Wide‐Bandgap Perovskite/Gallium Arsenide Tandem Solar Cells

“…Because high‐performance and stable perovskites having comparable wide bandgap to the conventional InGaP were demonstrated and integrated on GaAs bottom‐cell, potentially similar theoretical SQ efficiency limits to those of InGaP/GaAs tandem cells would be expected from this approach (over 40% maximum efficiency with around 1.9 eV top‐cell on GaAs bottom‐cell in 2T configuration), which are based on the detailed balance analysis assuming perfect absorption of photons having energy above the bandgap in each subcell without reflection losses (Figure S17, Supporting Information). For further realistic improvement of overall PCE, especially in this system, suppressing reflection loss from the structure, as high as 2.2 mA cm −2 (Figure d), with light‐trapping structure and reducing parasitic absorption mainly from charge‐transporting layers and TCOs, around 4.7 mA cm −2 (Figure d: 1.13 mA cm −2 from blue region and 3.57 mA cm −2 from NIR region), with alternative transparent electrodes would be beneficial to increase J sc . Moreover, further decrease of V oc deficit of high bandgap perovskite and extension of GaAs p‐n junction to heterojunction structure (e.g., GaAs‐AlGaAs) for approaching 1.13 V could enhance the overall V oc of tandem cell.…”