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Controlling the perovskite morphology and defects at the buried perovskite-substrate interface is challenging for inverted perovskite solar cells. In this work, we report an amphiphilic molecular hole transporter, (2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanovinyl)phosphonic acid, that features a multifunctional cyanovinyl phosphonic acid group and forms a superwetting underlayer for perovskite deposition, which enables high-quality perovskite films with minimized defects at the buried interface. The resulting perovskite film has a photoluminescence quantum yield of 17% and a Shockley-Read-Hall lifetime of nearly 7 microseconds and achieved a certified power conversion efficiency (PCE) of 25.4% with an open-circuit voltage of 1.21 volts and a fill factor of 84.7%. In addition, 1–square centimeter cells and 10–square centimeter minimodules show PCEs of 23.4 and 22.0%, respectively. Encapsulated modules exhibited high stability under both operational and damp heat test conditions.

With power conversion efficiencies of perovskite-on-silicon and all-perovskite tandem solar cells increasing at rapid pace, wide bandgap (> 1.7 eV) metal-halide perovskites (MHPs) are becoming a major focus of academic and industrial photovoltaic research. Compared to their lower bandgap (< 1.6 eV) counterparts, these types of perovskites suffer from higher levels of non-radiative losses in both the bulk material and in device configurations, constraining their efficiencies far below their thermodynamic potential. In this work, we investigate the energy losses in methylammonium (MA) free high-Br-content widegap perovskites by using a combination of THz spectroscopy, steady-state and time-resolved photoluminescence, coupled with drift-diffusion simulations. The investigation of this system allows us to study charge-carrier recombination in these materials and devices in the absence of halide segregation due to the photostabilty of formamidinium-cesium based lead halide perovskites. We find that these perovskites are characterised by large non-radiative recombination losses in the bulk material and that the interfaces with transport layers in solar cell devices strongly limit their open-circuit voltage. In particular, we discover that the interface with the hole transport layer performs particularly poorly, in contrast to 1.6 eV bandgap MHPs which are generally limited by the interface with the electron-transport layer. To overcome these losses, we incorporate and investigate the recombination mechanisms present with perovskites treated with the ionic additive 1-butyl-1-methylpipiderinium tetrafluoroborate. We find that this additive not only improves the radiative efficiency of the bulk perovskite, but also reduces the non-radiative recombination at both the hole and electron transport layer interfaces of full photovoltaic devices. In addition to unravelling the beneficial effect of this specific treatment, we further optimise our solar cells by introducing an additional LiF interface treatment at the electron transport layer interface. Together these treatments enable MA-free 1.79 eV bandgap perovskite solar cells with open-circuit voltages of 1.22 V and power conversion efficiencies approaching 17 %, which is among the highest reported for this material system.

In the last decade, perovskite semiconductors have triggered a revolution in solar cell research. However, critical issues remain concerning the stability of metal-halide perovskites, which need to be overcome to enable a large scale commercialisation of perovskite photovoltaics (PV). While the rather poor environmental stability of these perovskites is usually attributed to their ionic nature rendering them sensitive to moisture and oxygen, the actual contribution of mobile ions to the total degradation loss under different environmental conditions is poorly understood. In this work, we reveal that the initial degradation of perovskite semiconductors is largely the result of mobile ion-induced internal field screening - a phenomenon that has not been previously discussed in relation to the degradation of perovskite solar cells. The increased field screening leads to a decrease in the steady-state power conversion efficiency mainly due to a large reduction in current density, while the efficiency at high scan speeds (>1000 V/s) where the ions are immobilized is much less affected. We also show that interfacial recombination does not increase upon ageing, yet the open-circuit voltage (VOC) decreases as the result of an increase in the mobile ion density upon ageing. Furthermore, similar ionic losses appear under different external stressors, in particular when there are free charges present in the absorber layer. This work reveals a key degradation mechanism, providing new insights into initial device degradation before chemical or extrinsic mechanical device degradation effects manifest, and it highlights the critical role mobile ions play therein.

In crystalline and amorphous semiconductors, the temperature-dependent Urbach energy can be determined from the inverse slope of the logarithm of the absorption spectrum and reflects the static and dynamic energetic disorder. Using recent advances in the sensitivity of photocurrent spectroscopy methods, we elucidate the temperature-dependent Urbach energy in lead halide perovskites containing different numbers of cation components. We find Urbach energies at room temperature to be 13.0 ± 1.0, 13.2 ± 1.0, and 13.5 ± 1.0 meV for single, double, and triple cation perovskite. Static, temperature-independent contributions to the Urbach energy are found to be as low as 5.1 ± 0.5, 4.7 ± 0.3, and 3.3 ± 0.9 meV for the same systems. Our results suggest that, at a low temperature, the dominant static disorder in perovskites is derived from zero-point phonon energy rather than structural disorder. This is unusual for solution-processed semiconductors but broadens the potential application of perovskites further to quantum electronics and devices.

Flexible all-perovskite tandem photovoltaics open up new opportunities for application compared to rigid devices, yet their performance lags behind. Now, researchers show that molecule-bridged interfaces mitigate charge recombination and crack formation, improving the efficiency and mechanical reliability of flexible devices.

This work investigates halide segregation in methylammonium-free wide bandgap perovskites by photoluminescence quantum yield (PLQY) and advanced electron microscopy techniques. Our study reveals ho...

Inverted perovskite solar cells still suffer from significant non-radiative recombination losses at the perovskite surface and across the perovskite/C

Perovskite/silicon tandem solar cells allow to overcome the power conversion efficiency limit of market-dominating silicon solar cells. So far, various textured tandem devices were presented aiming at improved optical performance, but highest efficiencies were still realized on polished silicon wafer cells enabling superior perovskite layer properties. Here we present perovskite/silicon tandem solar cells with gentle periodic nanotextures which feature various advantages without compromising the material quality of solution-processed perovskite layers. Reflection losses are reduced in comparison to planar tandems and the devices are less sensitive upon deviations from optimum layer thicknesses. The nanotextures also enable excellent perovskite film formation and a greatly increased fabrication yield. The open-circuit voltage improved by about 15 mV due to enhanced electronic properties of the perovskite top cell. In addition, an optically advanced rear reflector with a dielectric buffer layer reduced parasitic absorption at near-infrared wavelengths. Altogether, the improvements enabled a certified power conversion efficiency of 29.80%.

Perovskite-silicon tandem solar cells offer the possibility of overcoming the power conversion efficiency limit of conventional silicon solar cells. Various textured tandem devices have been presented aiming at improved optical performance, but optimizing film growth on surface-textured wafers remains challenging. Here we present perovskite-silicon tandem solar cells with periodic nanotextures that offer various advantages without compromising the material quality of solution-processed perovskite layers. We show a reduction in reflection losses in comparison to planar tandems, with the new devices being less sensitive to deviations from optimum layer thicknesses. The nanotextures also enable a greatly increased fabrication yield from 50% to 95%. Moreover, the open-circuit voltage is improved by 15 mV due to the enhanced optoelectronic properties of the perovskite top cell. Our optically advanced rear reflector with a dielectric buffer layer results in reduced parasitic absorption at near-infrared wavelengths. As a result, we demonstrate a certified power conversion efficiency of 29.80%.

Donor polymer number-average molar mass (Mn) has long been known to influence organic photovoltaic (OPV) performance via changes in both the polymer properties and the resulting bulk heterojunction...

Perovskites offer exciting opportunities to realize efficient multijunction photovoltaic devices. This requires high-VOC and often Br-rich perovskites, which currently suffer from halide segregatio...

Multication metal-halide perovskites exhibit desirable performance and stability, compared to their monocation counterparts. However, the study of the photophysical properties and the nature of defect states in these materials is still a challenging and ongoing task. Here, we study bulk and interfacial energy loss mechanisms in solution-processed MAPbI3 (MAPI) and (CsPbI3)0.05[(FAPbI3)0.83(MAPbBr3)0.17]0.95 (triple cation) perovskite solar cells using absolute photoluminescence (PL) measurements. In neat MAPI films, we find a significantly smaller quasi-Fermi level splitting than for the triple cation perovskite absorbers, which defines the open-circuit voltage of the MAPI cells. PL measurements at low temperatures (∼20 K) on MAPI films demonstrate that emissive subgap states can be effectively reduced using different passivating agents, which lowers the nonradiative recombination loss at room temperature. We conclude that while triple cation perovskite cells are limited by interfacial recombination, the passivation of surface trap states within the MAPI films is the primary consideration for device optimization.

Recent work on bulk-heterojunction organic solar cells has shown that photoexcitation of the electron acceptor followed by photoinduced hole transfer can play a significant role in photocurrent generation. To establish a clear understanding of the role of the donor in the photoinduced hole transfer process, we have synthesized a series of triphenylamine-based hole-transporting poly(dendrimer)s with mechanically flexible nonconjugated backbones via ring-opening metathesis polymerization and used them in low donor content solar cells. The poly(dendrimer)s were found to retain the hole transporting properties of the parent dendrimer, with hole mobilities of similar to 10(-3) cm(2)/(V s) for solution processed neat films. However, when blended with [6,6]-phenyl-C-70-butyric acid methyl ester (PC70BM), the best performing poly(dendrimer) was found to form films that had balanced and relatively high hole/electron mobilities of similar to 5 x 10(-4) cm(2) /(V s). In contrast, at the same concentration the parent dendrimer:PC70BM blend was found to have a hole mobility of 4 orders of magnitude less than the electron mobility. The balanced hole and electron mobilities for the 6 wt % poly(dendrimer):PC70BM blend led to an absence of second-order bimolecular recombination losses at the maximum power point and resulted in a fill factor of 0.65 and a PCE 2.1% for the devices, which was almost three times higher than the cells composed of the parent dendrimer:PC70BM blends.

Traditional inorganic semiconductors can be electronically doped with high precision. Conversely, there is still conjecture regarding the assessment of the electronic doping density in metal-halide perovskites, not to mention of a control thereof. This paper presents a multifaceted approach to determine the electronic doping density for a range of different lead-halide perovskite systems. Optical and electrical characterization techniques, comprising intensity-dependent and transient photoluminescence, AC Hall effect, transfer-length-methods, and charge extraction measurements were instrumental in quantifying an upper limit for the doping density. The obtained values are subsequently compared to the electrode charge per cell volume under short-circuit conditions ([Formula: see text]), which amounts to roughly 1016 cm−3. This figure of merit represents the critical limit below which doping-induced charges do not influence the device performance. The experimental results consistently demonstrate that the doping density is below this critical threshold (∼1012 cm−3, which means ≪ [Formula: see text]) for all common lead-based metal-halide perovskites. Nevertheless, although the density of doping-induced charges is too low to redistribute the built-in voltage in the perovskite active layer, mobile ions are present in sufficient quantities to create space-charge-regions in the active layer, reminiscent of doped pn-junctions. These results are well supported by drift–diffusion simulations, which confirm that the device performance is not affected by such low doping densities.

Funder: Alexander von Humboldt Foundation; Id: http://dx.doi.org/10.13039/100005156, Perovskite semiconductors are an attractive option to overcome the limitations of established silicon based photovoltaic (PV) technologies due to their exceptional opto‐electronic properties and their successful integration into multijunction cells. However, the performance of single‐ and multijunction cells is largely limited by significant nonradiative recombination at the perovskite/organic electron transport layer junctions. In this work, the cause of interfacial recombination at the perovskite/C60 interface is revealed via a combination of photoluminescence, photoelectron spectroscopy, and first‐principle numerical simulations. It is found that the most significant contribution to the total C60‐induced recombination loss occurs within the first monolayer of C60, rather than in the bulk of C60 or at the perovskite surface. The experiments show that the C60 molecules act as deep trap states when in direct contact with the perovskite. It is further demonstrated that by reducing the surface coverage of C60, the radiative efficiency of the bare perovskite layer can be retained. The findings of this work pave the way toward overcoming one of the most critical remaining performance losses in perovskite solar cells.

Halide perovskite-based photon upconverters utilize perovskite thin films to sensitize triplet exciton formation in a small-molecule layer, driving triplet-triplet annihilation upconversion. Despite having excellent carrier mobility, these systems suffer from inefficient triplet formation at the perovskite/annihilator interface. We studied triplet formation in formamidinium-methylammonium lead iodide/rubrene bilayers using photoluminescence and surface photovoltage methods. By studying systems constructed on glass as well as hole-selective substrates, comprising self-assembled layers of the carbazole derivative 2PACz ([2-(9H-carbazol-9-yl)ethyl]phosphonic acid) on indium-doped tin oxide, we saw how changes in the carrier dynamics induced by the hole-selective substrate perturbed triplet formation at the perovskite/rubrene interface. We propose that an internal electric field, caused by hole transfer at the perovskite/rubrene interface, strongly affects triplet exciton formation, accelerating exciton-forming electron-hole encounters at the interface but also limiting the hole density in rubrene at high excitation densities. Controlling this field is a promising path to improving triplet formation in perovskite/annihilator upconverters.

Perovskite–silicon tandem solar cells offer the possibility of overcoming the power conversion efficiency limit of conventional silicon solar cells. Various textured tandem devices have been presented aiming at improved optical performance, but optimizing film growth on surface-textured wafers remains challenging. Here we present perovskite–silicon tandem solar cells with periodic nanotextures that offer various advantages without compromising the material quality of solution-processed perovskite layers. We show a reduction in reflection losses in comparison to planar tandems, with the new devices being less sensitive to deviations from optimum layer thicknesses. The nanotextures also enable a greatly increased fabrication yield from 50% to 95%. Moreover, the open-circuit voltage is improved by 15 mV due to the enhanced optoelectronic properties of the perovskite top cell. Our optically advanced rear reflector with a dielectric buffer layer results in reduced parasitic absorption at near-infrared wavelengths. As a result, we demonstrate a certified power conversion efficiency of 29.80%.

Among various types of perovskite based tandem solar cells TSCs , all perovskite TSCs are of particular attractiveness for building and vehicle integrated photovoltaics, or space energy areas as they can be fabricated on flexible and lightweight substrates with a very high power to weight ratio. However, the efficiency of flexible all perovskite tandems is lagging far behind their rigid counterparts primarily due to the challenges in developing efficient wide bandgap WBG perovskite solar cells on the flexible substrates as well as their low open circuit voltage VOC . Here, it is reported that the use of self assembled monolayers as hole selective contact effectively suppresses the interfacial recombination and allows the subsequent uniform growth of a 1.77 eV WBG perovskite with superior optoelectronic quality. In addition, a postdeposition treatment with 2 thiopheneethylammonium chloride is employed to further suppress the bulk and interfacial recombination, boosting the VOC of the WBG top cell to 1.29 V. Based on this, the first proof of concept four terminal all perovskite flexible TSC with a power conversion efficiency of 22.6 is presented. When integrating into two terminal flexible tandems, 23.8 flexible all perovskite TSCs with a superior VOC of 2.1 V is achieved, which is on par with the VOC reported on the 28 all perovskite tandems grown on the rigid substrate

Mobilities and lifetimes of photogenerated charge carriers are core properties of photovoltaic materials and can both be characterized by contactless terahertz or microwave measurements. Here, the expertise from fifteen laboratories is combined to quantitatively model the current-voltage characteristics of a solar cell from such measurements. To this end, the impact of measurement conditions, alternate interpretations, and experimental inter-laboratory variations are discussed using a (Cs,FA,MA)Pb(I,Br)3 halide perovskite thin-film as a case study. At 1 sun equivalent excitation, neither transport nor recombination is significantly affected by exciton formation or trapping. Terahertz, microwave, and photoluminescence transients for the neat material yield consistent effective lifetimes implying a resistance-free JV-curve with a potential power conversion efficiency of 24.6 %. For grainsizes above ≈20 nm, intra-grain charge transport is characterized by terahertz sum mobilities of ≈32 cm2 V−1 s−1. Drift-diffusion simulations indicate that these intra-grain mobilities can slightly reduce the fill factor of perovskite solar cells to 0.82, in accordance with the best-realized devices in the literature. Beyond perovskites, this work can guide a highly predictive characterization of any emerging semiconductor for photovoltaic or photoelectrochemical energy conversion. A best practice for the interpretation of terahertz and microwave measurements on photovoltaic materials is presented.

We present results on perovskite/silicon tandem solar cells with almost 30% power conversion efficiency. They comprise sinusoidal nanotextures between top and bottom cells and optically advanced rear reflectors with a dielectric buffer layer.

In contrast to the common conception that the interfacial energy-level alignment is affixed once the interface is formed, we demonstrate that heterojunctions between organic semiconductors and metal-halide perovskites exhibit huge energy-level realignment during photoexcitation. Importantly, the photoinduced level shifts occur in the organic component, including the first molecular layer in direct contact with the perovskite. This is caused by charge-carrier accumulation within the organic semiconductor under illumination and the weak electronic coupling between the junction components.

Charge extraction in organic solar cells (OSCs) is commonly believed to be limited by bimolecular recombination of photogenerated charges. However, the fill factor of OSCs is usually almost entirely governed by recombination processes that scale with the first order of the light intensity. This linear loss was often interpreted to be a consequence of geminate or trap-assisted recombination. Numerical simulations show that this linear dependence is a direct consequence of the large amount of excess dark charge near the contact. The first-order losses increase with decreasing mobility of minority carriers, and we discuss the impact of several material and device parameters on this loss mechanism. This work highlights that OSCs are especially vulnerable to injected charges as a result of their poor charge transport properties. This implies that dark charges need to be better accounted for when interpreting electro-optical measurements and charge collection based on simple figures of merit.

We have synthesised new materials comprised of 9,9′-bifluorenylidene and dithienodiketopyrrolopyrrole units. While 9,9′-bifluorenylidene has been primarily used in non-fullerene acceptors, when used in combination with the diketopyrrolopyrrole moiety it can form donor materials that can be used in conjunction with fullerene acceptors. The compounds differ in the substituents on the 9,9′-bifluorenylidene (protonated = 1A and dimethoxy = 1B) moiety. The structure of both the neat and blend films with PC70BM were found to be strongly dependent on the processing solvent used. In particular, Grazing Incidence Wide Angle X-ray Scattering measurements of films of 1A or 1B blended with PC70BM prepared from chloroform or chloroform with o-dichlorobenzene as an additive showed that the donor material had no particular ordering. However, when 1,8-diiodooctane was added to the processing solvent the 1A blends showed liquid crystalline ordering while 1B formed well-defined crystallites with three-dimensional ordering. The difference in film structure had a profound effect on the device properties. For 1A the optimised blend ratio with PC70BM was 1:4, but when 1,8-diiodooctane was used as the additive the best ratio of 1A to fullerene was 1:1. The films containing the well-defined crystallites of 1B all performed poorly, which was ascribed to a lack of a percolation pathway for hole extraction. The best performing device was comprised of a 1:1 blend of 1A and PC70BM, which had a power conversion efficiency of 2.6%.

The incorporation of even small amounts of strontium (Sr) into lead-base hybrid quadruple cation perovskite solar cells results in a systematic increase of the open circuit voltage (V-oc) in pin-type perovskite solar cells. We demonstrate via absolute and transient photoluminescence (PL) experiments how the incorporation of Sr significantly reduces the non-radiative recombination losses in the neat perovskite layer. We show that Sr segregates at the perovskite surface, where it induces important changes of morphology and energetics. Notably, the Sr-enriched surface exhibits a wider band gap and a more n-type character, accompanied with significantly stronger surface band bending. As a result, we observe a significant increase of the quasi-Fermi level splitting in the neat perovskite by reduced surface recombination and more importantly, a strong reduction of losses attributed to non-radiative recombination at the interface to the C-60 electron-transporting layer. The resulting solar cells exhibited a V-oc of 1.18 V, which could be further improved to nearly 1.23 V through addition of a thin polymer interlayer, reducing the non-radiative voltage loss to only 110 meV. Our work shows that simply adding a small amount of Sr to the precursor solutions induces a beneficial surface modification in the perovskite, without requiring any post treatment, resulting in high efficiency solar cells with power conversion efficiency (PCE) up to 20.3%. Our results demonstrate very high V-oc values and efficiencies in Sr-containing quadruple cation perovskite pin-type solar cells and highlight the imperative importance of addressing and minimizing the recombination losses at the interface between perovskite and charge transporting layer.

Charge transport layers (CTLs) are key components of diffusion controlled perovskite solar cells, however, they can induce additional non-radiative recombination pathways which limit the open circuit voltage (V-OC) of the cell. In order to realize the full thermodynamic potential of the perovskite absorber, both the electron and hole transport layer (ETL/HTL) need to be as selective as possible. By measuring the photoluminescence yield of perovskite/CTL heterojunctions, we quantify the non-radiative interfacial recombination currents in pin- and nip-type cells including high efficiency devices (21.4%). Our study comprises a wide range of commonly used CTLs, including various hole-transporting polymers, spiro-OMeTAD, metal oxides and fullerenes. We find that all studied CTLs limit the V-OC by inducing an additional non-radiative recombination current that is in most cases substantially larger than the loss in the neat perovskite and that the least-selective interface sets the upper limit for the V-OC of the device. Importantly, the V-OC equals the internal quasi-Fermi level splitting (QFLS) in the absorber layer only in high efficiency cells, while in poor performing devices, the V-OC is substantially lower than the QFLS. Using ultraviolet photoelectron spectroscopy and differential charging capacitance experiments we show that this is due to an energy level mis-alignment at the p-interface. The findings are corroborated by rigorous device simulations which outline important considerations to maximize the V-OC. This work highlights that the challenge to suppress non-radiative recombination losses in perovskite cells on their way to the radiative limit lies in proper energy level alignment and in suppression of defect recombination at the interfaces.

Open-circuit voltages of lead-halide perovskite solar cells are improving rapidly and are approaching the thermodynamic limit. Since many different perovskite compositions with different bandgap energies are actively being investigated, it is not straightforward to compare the open-circuit voltages between these devices as long as a consistent method of referencing is missing. For the purpose of comparing open-circuit voltages and identifying outstanding values, it is imperative to use a unique, generally accepted way of calculating the thermodynamic limit, which is currently not the case. Here a meta-analysis of methods to determine the bandgap and a radiative limit for open-circuit voltage is presented. The differences between the methods are analyzed and an easily applicable approach based on the solar cell quantum efficiency as a general reference is proposed., Zweitver��ffentlichungen der Universit��t Potsdam : Mathematisch-Naturwissenschaftliche Reihe; 1194

Recent advancements in perovskite solar cell performance were achieved by stabilizing the α-phase of FAPbI3 in nip-type architectures. However, these advancements could not be directly translated to pin-type devices. Here, we fabricated a high-quality double cation perovskite (MA0.07FA0.93PbI3) with low bandgap energy (1.54 eV) using a two-step approach on a standard polymer (PTAA). The perovskite films exhibit large grains (∼1 μm), high external photoluminescence quantum yields of 20%, and outstanding Shockley-Read-Hall carrier lifetimes of 18.2 μs without further passivation. The exceptional optoelectronic quality of the neat material was translated into efficient pin-type cells (up to 22.5%) with improved stability under illumination. The low-gap cells stand out by their high fill factor (∼83%) due to reduced charge transport losses and short-circuit currents >24 mA cm-2. Using intensity-dependent quasi-Fermi level splitting measurements, we quantify an implied efficiency of 28.4% in the neat material, which can be realized by minimizing interfacial recombination and optical losses.

Interfaces play a crucial role in determining perovskite solar cells, (PSCs) performance and stability. It is therefore of great importance to constantly work toward improving their design. This study shows the advantages of using a hole-transport material (HTM) that can anchor to the perovskite surface through halogen bonding (XB). A halo-functional HTM (PFI) is compared to a reference HTM (PF), identical in optoelectronic properties and chemical structure but lacking the ability to form XB. The interaction between PFI and perovskite is supported by simulations and experiments. XB allows the HTM to create an ordered and homogenous layer on the perovskite surface, thus improving the perovskite/HTM interface and its energy level alignment. Thanks to the compact and ordered interface, PFI displays increased resistance to solvent exposure compared to its not-interacting counterpart. Moreover, PFI devices show suppressed nonradiative recombination and reduced hysteresis, with a Voc enhancement of ≥20 mV and a remarkable stability, retaining more than 90% efficiency after 550 h of continuous maximum-power-point tracking. This work highlights the potential that XB can bring to the context of PSCs, paving the way for a new halo-functional design strategy for charge-transport layers, which tackles the challenges of charge transport and interface improvement simultaneously. publishedVersion

Perovskite semiconductors have demonstrated outstanding external luminescence quantum yields, enabling high power conversion efficiencies PCEs . However, the precise conditions to advance to an efficiency regime above monocrystalline silicon cells are not well understood. Herein, a simulation model that describes efficient p i n type perovskite solar cells well and a range of different experiments is established. Then, important device and material parameters are studied and it is found that an efficiency regime of 30 can be unlocked by optimizing the built in voltage across the perovskite layer using either highly doped 1019 amp; 8201;cm amp; 8722;3 transport layers TLs , doped interlayers or ultrathin self assembled monolayers. Importantly, only parameters that have been reported in recent literature are considered, that is, a bulk lifetime of 10 amp; 8201; amp; 956;s, interfacial recombination velocities of 10 amp; 8201;cm amp; 8201;s amp; 8722;1, a perovskite bandgap amp; 119864;gap of 1.5 amp; 8201;eV, and an external quantum efficiency EQE of 95 . A maximum efficiency of 31 is predicted for a bandgap of 1.4 amp; 8201;eV. Finally, it is demonstrated that the relatively high mobile ion density does not represent a significant barrier to reach this efficiency regime. The results of this study suggest continuous PCE improvements until perovskites may become the most efficient single junction solar cell technology in the near future