Overcoming the Photovoltage Plateau in Large Bandgap Perovskite Photovoltaics

Abstract

Development of large bandgap (1.80-1.85 eV E) perovskite is crucial for perovskite-perovskite tandem solar cells. However, the performance of 1.80-1.85 eV E perovskite solar cells (PVKSCs) are significantly lagging their counterparts in the 1.60-1.75 eV E range. This is because the photovoltage ( V) does not proportionally increase with E due to lower optoelectronic quality of conventional (MA,FA,Cs)Pb(I,Br) and results in a photovoltage plateau ( V limited to 80% of the theoretical limit for ∼1.8 eV E). Here, we incorporate phenylethylammonium (PEA) in a mixed-halide perovskite composition to solve the inherent material-level challenges in 1.80-1.85 eV E perovskites. The amount of PEA incorporation governs the topography and optoelectronic properties of resultant films. Detailed structural and spectroscopic characterization reveal the characteristic trends in crystalline size, orientation, and charge carrier recombination dynamics and rationalize the origin of improved material quality with higher luminescence. With careful interface optimization, the improved material characteristics were translated to devices and V values of 1.30-1.35 V were achieved, which correspond to 85-87% of the theoretical limit. Using an optimal amount of PEA incorporation to balance the increase in V and the decrease in charge collection, a highest power conversion efficiency of 12.2% was realized. Our results clearly overcome the photovoltage plateau in the 1.80-1.85 eV E range and represent the highest V achieved for mixed-halide PVKSCs. This study provides widely translatable insights, an important breakthrough, and a promising platform for next-generation perovskite tandems.

Two‐Terminal Perovskites Tandem Solar Cells: Recent Advances and Perspectives

“…Further improvements in V OC have been achieved by the same group, through the incorporation of phenethylammonium iodide (PEA) into MAPb(I 0.6 Br 0.4 ) 3 . It was found that lower photovoltage for conventional (MA,FA,Cs)Pb(I,Br) 3 was attributed to lower optoelectronic quality and resultant photovoltage plateau ( V OC limited to 80% of the theoretical limit for ≈1.8 eV E g ).…”

“…Based on the compositional versatility of metal halide perovskites (ABX 3 ), the most commonly used approaches for bandgap tuning include A-site compositional engineering (FA/Cs), [22,35,40,44] B-site modification (Pb/Sn binary alloys) [87][88][89] and incorporation of Br at the C-site. [40,45,90] The inclusion of FA/Cs into highbandgap mixed-halide perovskites can significantly increase the stability and energetic order, while reducing the tendency toward phase-segregation. The presence of MA cation can reduce a substantial lattice mismatch between Cs and FA and, thereby, slow down the perovskite crystallization process to achieve defect-free films.…”

“…Further improvements in V OC have been achieved by the same group, [90] through the incorporation of phenethylammonium Figure 9. All-perovskite monolithic tandem devices with high V OC : a) schematic illustration, b) cross-section SEM image, c) simulated electric field intensity distribution within a tandem stack, d) J-V curves, e) EQE, and f) steady-state current of the tandem device.…”

Wide‐Bandgap Perovskite/Gallium Arsenide Tandem Solar Cells

“…They also have negligible hysteresis depending on the scan direction (Figures S10c and S11c, Supporting Information) and rate (Figures S10d and S11d, Supporting Information), and their PCEs at the MPP (13.19 ± 0.09% and 12.75 ± 0.09% PCE for 1.87 and 1.89 eV, respectively) are comparable to those obtained by J – V scanning (Figures S10e and S11e, Supporting Information). Figure g and Table S2 (Supporting Information) summarize the recently reported performances of opaque wide‐bandgap perovskite PVs having their bandgap between 1.80 and 1.90 eV, and it is worth to note that, to the best of our knowledge, the wide‐bandgap perovskite PVs in this work show superior efficiencies in this bandgap range . Some of them represented higher V oc than our PV devices, but they had much lower J sc and FF, decreasing overall PCE (Table S2, Supporting Information).…”

“…Figure g and Table S2 (Supporting Information) summarize the recently reported performances of opaque wide‐bandgap perovskite PVs having their bandgap between 1.80 and 1.90 eV, and it is worth to note that, to the best of our knowledge, the wide‐bandgap perovskite PVs in this work show superior efficiencies in this bandgap range . Some of them represented higher V oc than our PV devices, but they had much lower J sc and FF, decreasing overall PCE (Table S2, Supporting Information).…”