Optical and Electronic Losses Arising from Physically Mixed Interfacial Layers in Perovskite Solar Cells

Subedi, Biwas; Song, Zhaoning; Chen, Cong; Ghimire, Kiran; Subedi, Indra; Yan, Yanfa; Podraza, Nikolas J.

doi:10.1021/acsami.0c16364

Cited by 19 publications

(32 citation statements)

References 40 publications

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“…34 The perovskite film thicknesses were obtained from the spectroscopic ellipsometry measurements and analysis as discussed in our earlier works. [16][17][18]22,35 E U was determined by the inverse of the slope of a linear fit to ln(α/α g ) below E g , and E g values for all the samples were obtained from Tauc plots 36 of the spectra in α. For MA 0.4 FA 0.6 Pb 1−x Sn x I 3 , (MAPbI 3 ) 1−x (FASnI 3 ) x , CsPb 1−y Sn y (I 1−x Br x ), CsPb 1−x Sn x I 3 , and MA x Cs 1−x PbBr 3 perovskite films, the spectra in α obtained from the PDS measurements were used to calculate the E g values.…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

Urbach Energy and Open-Circuit Voltage Deficit for Mixed Anion–Cation Perovskite Solar Cells

Subedi

Chen

et al. 2022

ACS Appl. Mater. Interfaces

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The Urbach energy indicating the width of the exponentially decaying sub-bandgap absorption tail is commonly used as the indicator of electronic quality of thin-film materials used as absorbers in solar cells. Urbach energies of hybrid inorganic−organic metal halide perovskites with various anion− cation compositions are measured by photothermal deflection spectroscopy. The variation in anion−cation composition has a substantial effect on the measured Urbach energy and hence the electronic quality of the perovskite. Depending upon the compositions, the Urbach energy varies from 18 to 65 meV for perovskite films with similar bandgap energies. For most of the perovskite compositions studied here including methylammonium (MA) + formamidinium (FA)-based Pb iodides, mixed Sn + Pb narrow-bandgap perovskites with low or intermediate Sn contents, and wide-bandgap FA + Cs-and I + Br-based perovskites, the correlation between the Urbach energy of the perovskite thin film and open-circuit voltage (V OC ) deficit for corresponding solar cells shows a direct relationship with reduction of the Urbach energy occurring with a beneficial decrease in the V OC deficit. However, due to issues related to material quality, impurity phases and stability in laboratory ambient air, and unoptimized film processing techniques, the solar cells incorporating Cs-based inorganic and mixed Sn + Pb perovskites with a higher than optimum Sn content show a higher V OC deficit even though the corresponding films show a lower Urbach energy.

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Section: ■ Experimental Methodsmentioning

confidence: 99%

Urbach Energy and Open-Circuit Voltage Deficit for Mixed Anion–Cation Perovskite Solar Cells

Subedi

Chen

et al. 2022

ACS Appl. Mater. Interfaces

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“…counterparts. 42,53,82,84 Such effects can also be seen in our literature survey of mixed tin−lead halide perovskites (Figure 4b) which indicates that for tin content between 0.5 and 20%, charge-carrier lifetimes rarely exceed 100 ns. Addition of minute fractions of tin to lead halide perovskites therefore appears to introduce non-radiative traps that are unlikely to be linked with changing band structure properties, as these vary only gradually from lead to tin halide perovskites.…”

Section: Charge-carrier Recombinationmentioning

confidence: 99%

Optoelectronic Properties of Tin–Lead Halide Perovskites

2021

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Mixed tin–lead halide perovskites have recently emerged as highly promising materials for efficient single- and multi-junction photovoltaic devices. This Focus Review discusses the optoelectronic properties that underpin this performance, clearly differentiating between intrinsic and defect-mediated mechanisms. We show that from a fundamental perspective, increasing tin fraction may cause increases in attainable charge-carrier mobilities, decreases in exciton binding energies, and potentially a slowing of charge-carrier cooling, all beneficial for photovoltaic applications. We discuss the mechanisms leading to significant bandgap bowing along the tin–lead series, which enables attractive near-infrared bandgaps at intermediate tin content. However, tin-rich stoichiometries still suffer from tin oxidation and vacancy formation which often obscures the fundamentally achievable performance, causing high background hole densities, accelerating charge-carrier recombination, lowering charge-carrier mobilities, and blue-shifting absorption onsets through the Burstein–Moss effect. We evaluate impacts on photovoltaic device performance, and conclude with an outlook on remaining challenges and promising future directions in this area.

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“…Another key factor contributing to the electrical losses in PSCs is the interfacial mixing layers, consisting of constitutes of perovskite and CTLs and voids. [144] The formation of a "dead" layer of the intermixing perovskite materials with a very high surface recombination velocity can lead to substantial losses in both J SC and V OC . [152,153] To avoid the formation of this high recombination layer, the possible detrimental chemical reactions between CTLs and halide perovskites need to be prevented by incorporating interface passivation or isolation layer.…”

Section: Electrical Lossesmentioning

confidence: 99%

“…Practical device architecture design needs to judiciously select materials based on their optical properties to minimize these optical losses in CTLs, which requires the accurate measurement of extinction coefficient (k) and refractive index (n) and the establishment of an optical database for all the component materials used in PSCs. [144,145] Some CTLs that are commonly used in high-efficiency monofacial PSCs, such as spiro-OMeTAD and PCBM, have significant parasitic absorption of visible light and are not suitable for bifacial applications. [146,147] Alternative materials, including spiro-TTB, [79] copper(I) thiocyanate (CuSCN), [72] PTAA/CuO x , [148] and C 60 /SnO 2 , [15] can be utilized in bifacial PSCs to mitigate the parasitic absorption losses in the CTLs.…”

Section: Optical Lossesmentioning

confidence: 99%

Perovskite Solar Cells Go Bifacial—Mutual Benefits for Efficiency and Durability

2021

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PV technologies need to advance further in terms of a substantial increase in PV module power generation, reduction in module prices, and improvement in long-term reliability, eventually realizing low levelized costs of electricity (LCOE) that are compatible with standard electricity prices in the energy market. The PV industry's future development necessitates increased attention to emerging techniques with the potential to achieve high power generation at low costs.Increasing the power output per unit area of solar panels at low additional manufacturing costs is crucial for further lowering the PV-generated electricity price. One of the simplest and inexpensive strategies for increasing the power output density of a solar panel is to harvest reflected and diffuse sunlight from the ground by employing bifacial designs. The concept of bifacial solar cells can date back to the 1960s, but the momentum to bring bifacial solar panels to the market has been gradually realized in the last decade as one of the latest technological advances in PV manufacturing. [4] The mainstream crystalline silicon (c-Si) PV module manufacturers are now producing bifacial silicon solar modules based on different cell technologies. The trend shows that bifacial solar cells and modules are increasingly important in today's PV market and may soon become the cost-effective PV standard. [5] Unlike c-Si solar cells, efficient bifacial designs have not been demonstrated in commercial inorganic thin-film PV technologies because the polycrystalline inorganic thin films suffer from short carrier lifetimes and high rear surface recombination, limiting their bifacial PV performance. Metal halide perovskite solar cells (PSCs) have generated great interest in the PV research and industry, owing to their fast-growing power conversion efficiencies (PCEs), [6] outstanding optoelectronic properties, [7] ease of production, [8] low estimated manufacturing costs, [9] and readiness to take steps toward commercialization. [10] Within a decade, PSCs have rapidly evolved from a newcomer to a leading competitor to rival other established PV technologies.The development of PSCs opens up a golden opportunity to realize efficient bifacial thin-film solar cells. Figure 1 depicts the bifacial architecture for PSCs, summarizes the unique optoelectronic properties of perovskites that enable high bifacial performance, and highlights the advantages of bifacial Bifacial solar cells hold the potential to achieve a higher power output per unit area than conventional monofacial devices without significantly increasing manufacturing costs. However, efficient bifacial designs are challenging to implement in inorganic thin-film solar cells because of their short carrier lifetimes and high rear surface recombination. The emergence of perovskite photovoltaic (PV) technology creates a golden opportunity to realize efficient bifacial thin-film solar cells, owing to their outstanding optoelectronic properties and unique features of device physics. More importantly, transparent cond...

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Optical and Electronic Losses Arising from Physically Mixed Interfacial Layers in Perovskite Solar Cells

Cited by 19 publications

References 40 publications

Urbach Energy and Open-Circuit Voltage Deficit for Mixed Anion–Cation Perovskite Solar Cells

Urbach Energy and Open-Circuit Voltage Deficit for Mixed Anion–Cation Perovskite Solar Cells

Optoelectronic Properties of Tin–Lead Halide Perovskites

Perovskite Solar Cells Go Bifacial—Mutual Benefits for Efficiency and Durability

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