Ligang Yuan

All-polymer solar cells (all-PSCs) are attractive as alternatives to fabricate thermally and mechanically stable solar cells, especially with recent improvements in their power conversion efficiency (PCE). In this work, efficient all-PSCs with near-infrared response (up to 850 nm) are developed using newly designed regioregular polymer donors with relatively narrow optical gap. These all-PSCs systems achieve PCEs up to 6.0% after incorporating fluorine into the polymer backbone. More importantly, these polymers exhibit absorbance that is complementary to previously reported wide bandgap polymer donors. Thus, the superior properties of the newly designed polymers afford opportunities to fabricate the first spectrally matched all-polymer tandem solar cells with high performance. A PCE of 8.3% is then demonstrated which is the highest efficiency so far for all-polymer tandem solar cells. The design of narrow bandgap polymers provides new directions to enhance the PCE of emerging single-junction and tandem all polymer solar cells.

By adopting D1-A-D2-A ternary structure, a pair of novel regioregular polymers, namely PBBSB and PBFSF, are synthesized. Benefiting from the new arrangement and molecular fluorination, the polymer exhibits relatively narrow optical gap, good intermolecular packing, and excellent charge transport. More importantly, it is shown that these functional donor polymers can achieve high efficiency in either single-junction or tandem all-polymer solar cells.

To solve the stability issues of perovskite solar cells (PSC), here a novel interface engineering strategy that a versatile ultrathin 2D perovskite (5-AVA)₂PbI₄ (5-AVA = 5-ammoniumvaleric acid) passivation layer that is in situ incorporated at the interface between (FAPbI₃)_0.88(CsPbBr₃)_0.12 and the hole transporting CuSCN is reported. Surface analysis using X-ray photoelectron spectroscopy confirms the formation of 2D perovskite. Hysteresis is reduced by the interfacial 2D layer, which could be ascribed to improvement of interfacial charge extraction efficiency, associated with suppression of recombination. Moreover, introduction of the interface passivating layer enhances the moisture stability and photostability as compared to the control perovskite film due to hydrophobic nature of 2D perovskite. The unencapsulated device retains 98% of the initial power conversion efficiency (PCE) after 63 d under moisture exposure of about 10% in the dark. A PCE of the control device is boosted from 13.72 to 16.75% as a consequence of enhanced open-circuit voltage (V_oc) and fill factor along with slightly increased short-circuit current density (J_sc), which results from reduced trap states of (FAPbI₃)_0.88(CsPbBr₃)_0.12 as evidenced by enhanced carrier lifetimes and charge extraction. The perovskite/hole transport material interface engineering gives insight into simultaneous improvements of PCE and device stability.

A versatile ultrathin 2D perovskite (5-AVA)₂PbI₄ (5-AVA = 5-ammoniumvaleric acid) interlayer is in situ incorporated at the back contact interface between perovskite and CuSCN, which reduces current–voltage hysteresis and improves simultaneously power conversion efficiency (PCE) and stability. An unencapsulated device retains 98% of the initial PCE after 63 days under 10% relative humidity in the dark.

Fast research progress on lead halide perovskite solar cells has been achieved in the past a few years. However, the presence of lead (Pb) in perovskite composition as a toxic element still remains a major issue for large-scale deployment. In this work, a novel and facile technique is presented to fabricate tin (Sn)-rich perovskite film using metal precursors and an alloying technique. Herein, the perovskite films are formed as a result of the reaction between Sn/Pb binary alloy metal precursors and methylammonium iodide (MAI) vapor in a chemical vapor deposition process carried out at 185 °C. It is found that in this approach the Pb/Sn precursors are first converted to (Pb/Sn)I₂ and further reaction with MAI vapor leads to the formation of perovskite films. By using Pb–Sn eutectic alloy, perovskite films with large grain sizes up to 5 µm can be grown directly from liquid phase metal. Consequently, using an alloying technique and this unique growth mechanism, a less-toxic and efficient perovskite solar cell with a power conversion efficiency (PCE) of 14.04% is demonstrated, while pure Sn and Pb perovskite solar cells prepared in this manner yield PCEs of 4.62% and 14.21%, respectively. It is found that this alloying technique can open up a new direction to further explore different alloy systems (binary or ternary alloys) with even lower melting point.

Sn-rich perovskite solar cells with large grains are fabricated from a Pb–Sn eutectic alloy in the liquid phase by using a chemical vapor deposition technique, resulting in a device power conversion efficiency of 14.04%, which is comparable with that of pure Pb devices and among the highest for Sn-rich binary Sn/Pb metal perovskite solar cells.

Endured, low-cost, and high-performance flexible perovskite solar cells (PSCs) featuring lightweight and mechanical flexibility have attracted tremendous attention for portable power source applications. However, flexible PSCs typically use expensive and fragile indium–tin oxide as transparent anode and high-vacuum processed noble metal as cathode, resulting in dramatic performance degradation after continuous bending or thermal stress. Here, all-carbon-electrode-based flexible PSCs are fabricated employing graphene as transparent anode and carbon nanotubes as cathode. All-carbon-electrode-based flexible devices with and without spiro-OMeTAD (2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene) hole conductor achieve power conversion efficiencies (PCEs) of 11.9% and 8.4%, respectively. The flexible carbon-electrode-based solar cells demonstrate superior robustness against mechanical deformation in comparison with their counterparts fabricated on flexible indium–tin oxide substrates. Moreover, all carbon-electrode-based flexible PSCs also show significantly enhanced stability compared to the flexible devices with gold and silver cathodes under continuous light soaking or 60 °C thermal stress in air, retaining over 90% of their original PCEs after 1000 h. The promising durability and stability highlight that flexible PSCs are fully compatible with carbon materials and pave the way toward the realization of rollable and low-cost flexible perovskite photovoltaic devices.

An endurable all-carbon-electrode-based flexible perovskite solar cell is developed, employing graphene as front transparent electrode and carbon nanotubes as back electrode. All-carbon-electrode-based flexible perovskite solar cells with and without the spiro-OMeTAD (2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene) hole transport material show power conversion efficiencies of 11.8% and 8.3%, respectively. Moreover, flexible devices demonstrate outstanding bending durability and thermal stability.

A series of new branched hole transporting materials (HTMs) containing two diphenylamine-substituted carbazole fragments linked by a nonconjugated methylenebenzene unit is synthesized and tested in perovskite solar cells. Synthesis of the investigated materials is performed by a simple two-step synthetic procedure providing a target product in high yield. The isolated materials demonstrate good thermal stability and majority of the investigated compounds exist in an amorphous state, which is advantageous as there is no risk of crystallization directly in the film. The highest charge drift mobility of µ₀ = 4 × 10⁻⁴ cm² V⁻¹ s⁻¹, measured at weak electric fields, is by ca. one order of magnitude higher than that of Spiro-OMeTAD under identical conditions. From the perovskite solar cell testing results, it can be seen that performance of two new HTMs (V885 and V911) is on a par with Spiro-OMeTAD. Due to the ease of synthesis, good thermal, optical and photophysical properties, this type of molecules hold great promise for practical application in commercial perovskite solar cells.

Branched hole transporting materials (HTMs), containing two diphenylamine substituted carbazole moieties linked by a nonconjugated fragment, are synthesized and tested in perovskite solar cells. They are synthesized by a simple two-step synthetic procedure providing target products in high yield. Testing in perovskite solar cells indicates that performance of new HTMs is on a par with Spiro-OMeTAD.

The thin-film photovoltaic material Cu₂ZnSnS₄ (CZTS) has drawn worldwide attention in recent years due to its earth-abundant, nontoxic element constitution, and remarkable photovoltaic performance. Although state-of-the-art power conversion efficiency is achieved by hydrazine-based methods, effort to fabricate such devices in a high throughput, environmental-friendly way is still highlydesired. Here a hydrazine-free all-solution-processed CZTS solar cell with Na₂S self-depleted back contact modification layer for the first time is demonstrated, using a ball-milled CZTS as light absorber, low-temperature solution-processed ZnO electron-transport layer as well as silver-nanowire transparent electrode. The inserting of Na₂S self-depleted layer is proven to effectively stabilize the CZTS/Mo interface by eliminating a detrimental phase segregation reaction between CZTS and Mo-coated soda lime glass, thus leading to a better crystallinity of CZTS light absorbing layer, enhanced carrier transportation at CZTS/Mo interface as well as a smaller series resistance. Furthermore, the self-depletion feature of the Na₂S modification layer also averts hole-transportation barrier within the devices. The results show the vital importance of interfacial engineering for these CZST devices and the Na₂S interface layer can be extended to other optoelectronic devices using Mo contact.

An all-solution-processed Cu₂ZnSnS₄ (CZTS) solar cell is realized for the first time. A Na₂S layer is inserted at the CZTS/Mo interface to eliminate phase segregation of CZTS. This layer has a self-depletion nature during thermal annealing and is superior to inert barrier in several aspects. Solar cells with such modification layer achieve comprehensive enhancement in photovoltaic performance.

A terthieno[3,2-b]thiophene (6T) based fused-ring low bandgap electron acceptor, 6TIC, is designed and synthesized for highly efficient nonfullerene solar cells. The chemical, optical, and physical properties, device characteristics, and film morphology of 6TIC are intensively studied. 6TIC shows a narrow bandgap with band edge reaching 905 nm due to the electron-rich π-conjugated 6T core and reduced resonance stabilization energy. The rigid, π-conjugated 6T also offers lower reorganization energy to facilitate very low V_OC loss in the 6TIC system. The analysis of film morphology shows that PTB7-Th and 6TIC can form crystalline domains and a bicontinuous network. These domains are enlarged when thermal annealing is applied. Consequently, the device based on PTB7-Th:6TIC exhibits a high power conversion efficiency (PCE) of 11.07% with a high J_SC > 20 mA cm⁻² and a high V_OC of 0.83 V with a relatively low V_OC loss (≈0.55 V). Moreover, a semitransparent solar cell based on PTB7-Th:6TIC exhibits a relatively high PCE (7.62%). The device can have combined high PCE and high J_SC is quite rare for organic solar cells.

Terthieno[3,2-b]thiophene (6T) based low bandgap fused-ring electron acceptor, 6TIC, is developed for highly efficient solar cells, which exhibits a high power conversion efficiency (PCE) of 11.07% with a high J_SC over 20 mA cm⁻² and a high V_OC of 0.83 V with a relatively low V_OC loss (≈0.55 V). Moreover, the semitransparent solar cell based on PTB7-Th:6TIC exhibits a very promising PCE of 7.62%.

In p-i-n planar perovskite solar cells (pero-SCs) based on methylammonium lead iodide (MAPbI₃) perovskite, high-quality MAPbI₃ film, perfect interfacial band alignment and efficient charge extracting ability are critical for high photovoltaic performance. In this work, a hydrophilic fullerene derivative [6,6]-phenyl-C₆₁-butyric acid-(3,4,5-tris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)phenyl)methanol ester (PCBB-OEG) is introduced as additive in the methylammonium iodide precursor solution in the preparation of MAPbI₃ perovskite film by two-step sequential deposition method, and obtained a top-down gradient distribution with an ultrathin top layer of PCBB-OEG. Meanwhile, a high-quality perovskite film with high crystallinity, less trap-states, and dense-grained uniform morphology can well grow on both hydrophilic (poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid)) and hydrophobic (polytriarylamine, PTAA) hole transport layers. When the PCBB-OEG-containing perovskite film (pero-0.1) is prepared in a p-i-n planar pero-SC with the configuration of ITO/PTAA/pero-0.1/[6,6]-phenyl-C₆₁-butyric acid methyl ester/Al, the device delivers a promising power conversion efficiency (PCE) of 20.2% without hysteresis, which is one of the few PCE over 20% for the p-i-n planar pero-SCs. Importantly, the pero-0.1-based device shows an excellent stability that can retain 98.4% of its initial PCE after being exposed for 300 h under ambient atmosphere with a high humidity, and the flexible pero-SCs based on pero-0.1 also demonstrate a promising PCE of 18.1%.

It is demonstrated that a new strategy of two-step method provides a simple way to develop high-quality perovskite film. The perovskite solar cells (pero-SCs) show a high power conversion efficiency (PCE) of 20.2% with an excellent device stability. This strategy can also be suitable for fabricating flexible pero-SC giving a promising PCE of 18.1%.

An efficient perovskite photovoltaic-thermoelectric hybrid device is demonstrated by integrating the hole-conductor-free perovskite solar cell based on TiO₂/ZrO₂/carbon structure and the thermoelectric generator. The whole solar spectrum of AM 1.5 G is fully utilized with the ≈1.55 eV band gap perovskite (5-AVA)_x(MA)_1−xPbI₃ absorbing the visible light and the carbon back contact absorbing the infrared light. The added thermoelectric generator improves the device performance by converting the thermal energy into electricity via the Seebeck effect. An optimized hybrid device is obtained with a maximum point power output of 20.3% and open-circuit voltage of 1.29 V under the irradiation of 100 mW cm⁻².

By utilizing the whole AM 1.5 G solar spectrum energy, an efficient perovskite photovoltaic-thermoelectric hybrid device is demonstrated by integrating the perovskite solar cell based on carbon electrode and the thermoelectric generator. An optimized hybrid device is obtained with a maximum point power output of 20.3% and open-circuit voltage of 1.29 V under the irradiation of 100 mW cm⁻².

As the race toward higher efficiency for inorganic/organic hybrid perovskite solar cells (PSCs) is becoming highly competitive, a design scheme to maximize carrier transport toward higher power efficiency has been urgently demanded. In this study, a hidden role of A-site cations of PSCs in carrier transport, which has been largely neglected is unraveled, i.e., tuning the Fröhlich electron–phonon (e–ph) coupling of longitudinal optical (LO) phonon by A-site cations. The key for steering Fröhlich polaron is to control the interaction strength and the number of proton (or lithium) coordination to halide ions. The coordination to I⁻ alleviates electron–phonon scattering by either decreasing the Born effective charge or absorbing the LO motion of I. This novel principle discloses low electron–phonon coupling in several promising organic cations including hydroxyl–ammonium cation (NH₃OH⁺), hydrazinium cation (NH₃NH₂⁺) and possibly Li⁺ solvating methylamine (Li⁺∙∙∙NH₂CH₃), on a par with methyl–ammonium cations. A new perspective on the role of A-site cations could help in improving power efficiency and accelerating the application of PSCs.

A hidden role of A-site cations in perovskite solar cells in steering Fröhlich polaron coupling is disclosed. Design principles suggest that A-site cations need to be close to halides and to maximize the coordination to halides. Based on first principles and many-body theory, organic cations such as NH₃OH⁺, LiNH₂CH₃⁺, and NH₃F⁺ are predicted to be promising.

In this work, a new strategy to design low-temperature (≤200 °C) sintered dye-sensitized solar cells (lt-DSSC) is reported to enhance charge collection efficiencies (η_coll), photoconversion efficiencies (η), and stabilities under continuous operation conditions. Realization of lt-DSSC is enabled by the integration of hybrid nanoparticles based on TiO₂-Ru(II) complex (TiO₂_Ru_IS)—obtained by in situ bottom-up construction of Ru(II) N3 dye-sensitized titania—into the photoelectrode. Incentives for the use of TiO₂_Ru_IS are i) dye stability due to its integration into the TiO₂ anatase network and ii) enhanced charge collection yield due to its significant resistance toward electron recombination with electrolytes. It is demonstrated that devices with single-layer photoelectrodes featuring blends of P25 and TiO₂_Ru_IS give rise to a 60% η_coll relative to a 46% η_coll for devices with P25-based photoelectrodes. Responsible for this trend is a better charge transport and a reduced electron recombination. When using a multilayered photoelectrode architecture with a top layer based only on TiO₂_Ru_IS, devices with an even higher η_coll (74%) featuring a η of around 8.75% and stabilities of 600 h are achieved. This represents the highest values reported for lt-DSSC to date.

New dye-titania hybrid nanoparticles, namely TiO₂_IS_Ru, consisting of the in situ incorporation of a Ru(II) dye inside the structure of the anatase nanoparticles during their synthesis are utilized for designing low temperature sintered dye-sensitized solar cells with high stability and unprecedented efficiencies.

Organic–inorganic hybrid perovskite solar cells (PVSCs) have become the front-running photovoltaic technology nowadays and are expected to profoundly impact society in the near future. However, their practical applications are currently hampered by the challenges of realizing high performance and long-term stability simultaneously. Herein, the development of inverted PVSCs is reported based on low temperature solution-processed CuCrO₂ nanocrystals as a hole-transporting layer (HTL), to replace the extensively studied NiO_x counterpart due to its suitable electronic structure and charge carrier transporting properties. A ≈45 nm thick compact CuCrO₂ layer is incorporated into an inverted planar configuration of indium tin oxides (ITO)/c-CuCrO₂/perovskite/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM)/bathocuproine (BCP)/Ag, to result in the high steady-state power conversion efficiency of 19.0% versus 17.1% for the typical low temperature solution-processed NiO_x-based devices. More importantly, the optimized CuCrO₂-based device exhibits a much enhanced photostability than the reference device due to the greater UV light-harvesting of the CuCrO₂ layer, which can efficiently prevent the perovskite film from intense UV light exposure to avoid associated degradation. The results demonstrate the promising potential of CuCrO₂ nanocrystals as an efficient HTL for realizing high-performance and photostable inverted PVSCs.

A new, multifunctional CuCrO₂ hole-transporting layer is developed and incorporated into the inverted perovskite solar cells. The CuCrO₂ layer with superior electronic and optical properties is proved to not only enhance the photovoltaic performance but also improve the device photostability via the UV-blocking effect. Consequently, a high power conversion efficiency of 19.0% with enhanced device photostability is successfully demonstrated.

Lead tri-iodide methylammonium (MAPbI₃) perovskite polycrystalline materials show complex optoelectronic behavior, largely because their 3D semiconducting inorganic framework is strongly perturbed by the organic cations and ubiquitous structural or chemical inhomogeneities. Here, a newly developed time-dependent density functional theory-based theoretical formalism is taken advantage of. It treats electron–hole and electron–nuclei interactions on the same footing to assess the many-body excited states of MAPbI₃ perovskites in their pristine state and in the presence of point chemical defects. It is shown that lead and iodine vacancies yield deep trap states that can be healed by dynamic effects, namely rotation of the methylammonium cations in response to point charges, or through slight changes in chemical composition, namely by introducing a tiny amount of chlorine dopants in the defective MAPbI₃. The theoretical results are supported by photoluminescence experiments on MAPbI_3−mCl_m and pave the way toward the design of defect-free perovskite materials with optoelectronic performance approaching the theoretical limits.

How methylammonium cations and chlorine dopants heal defects in lead tri-iodide methylammonium (MAPbI₃) perovskites is proposed. Time-dependent density functional theory excited-state calculations in defective MAPbI₃ show crossovers from confined to extended states when varying the electrostatic environment around vacancies. Deep trap states are dynamically healed through collective rotation of the methylammonium cations and by introducing tiny amounts of chlorine dopants.

Achieving light harvesting is crucial for the efficiency of the solar cell. Constructing optical structures often can benefit from micro-nanophotonic imprinting. Here, a simple and facile strategy is developed to introduce a large area grating structure into the perovskite-active layer of a solar cell by utilizing commercial optical discs (CD-R and DVD-R) and achieve high photovoltaic performance. The constructed diffraction grating on the perovskite active layer realizes nanophotonic light trapping by diffraction and effectively suppresses carrier recombination. Compared to the pristine perovskite solar cells (PSCs), the diffraction-grating perovskite devices with DVD obtain higher power conversion efficiency and photocurrent density, which are improved from 16.71% and 21.67 mA cm⁻² to 19.71% and 23.11 mA cm⁻². Moreover, the stability of the PSCs with diffraction-grating-structured perovskite active layer is greatly enhanced. The method can boost photonics merge into the remarkable perovskite materials for various applications.

Diffraction grating is introduced into a perovskite active layer via optical discs. The constructed architecture enhances light harvesting and photon-to-electron conversion efficiency by diffracting the incident light. Besides, it also improves the charge extraction process and suppresses electron–hole recombination. The diffraction-grating perovskite devices achieve a high power conversion efficiency of 19.71%.

The current work reports a high power conversion efficiency (PCE) of 9.54% achieved with nonfullerene organic solar cells (OSCs) based on PTB7-Th donor and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene) (ITIC) acceptor fabricated by doctor-blade printing, which has the highest efficiency ever reported in printed nonfullerene OSCs. Furthermore, a high PCE of 7.6% is realized in flexible large-area (2.03 cm²) indium tin oxide (ITO)-free doctor-bladed nonfullerene OSCs, which is higher than that (5.86%) of the spin-coated counterpart. To understand the mechanism of the performance enhancement with doctor-blade printing, the morphology, crystallinity, charge recombination, and transport of the active layers are investigated. These results suggest that the good performance of the doctor-blade OSCs is attributed to a favorable nanoscale phase separation by incorporating 0.6 vol% of 1,8-diiodooctane that prolongs the dynamic drying time of the doctor-bladed active layer and contributes to the migration of ITIC molecules in the drying process. High PCE obtained in the flexible large-area ITO-free doctor-bladed nonfullerene OSCs indicates the feasibility of doctor-blade printing in large-scale fullerene-free OSC manufacturing. For the first time, the open-circuit voltage is increased by 0.1 V when 1 vol% solvent additive is added, due to the vertical segregation of ITIC molecules during solvent evaporation.

Printed nonfullerene organic solar cells are investigated with a power conversion efficiency of 9.54% via incorporating a 1,8-diiodooctane additive for achieving a favorable nanoscale phase separation. The migration of nonfullerene acceptor molecules from bottom to top helps form the optimal donor/acceptor interface distribution, leading to the reduced exciton recombination and optimized electrical parameters.

Planar heterojunction perovskite solar cells are fabricated via low-temperature process with an architecture of ITO/SnO₂/Perovskite/Spiro-OMeTAD/Ag. The power conversion efficiency (PCE) of up to 20.51% with negligible hysteresis and a steady output PCE of 20.22% can be achieved, and ≈80% of the original PCEs can be maintained when exposed to air environment (humidity ≈40%) for over 500 hr without encapsulation.

The power conversion efficiency of perovskite solar cells (PSCs) has ascended from 3.8% to 22.1% in recent years. ZnO has been well-documented as an excellent electron-transport material. However, the poor chemical compatibility between ZnO and organo-metal halide perovskite makes it highly challenging to obtain highly efficient and stable PSCs using ZnO as the electron-transport layer. It is demonstrated in this work that the surface passivation of ZnO by a thin layer of MgO and protonated ethanolamine (EA) readily makes ZnO as a very promising electron-transporting material for creating hysteresis-free, efficient, and stable PSCs. Systematic studies in this work reveal several important roles of the modification: (i) MgO inhibits the interfacial charge recombination, and thus enhances cell performance and stability; (ii) the protonated EA promotes the effective electron transport from perovskite to ZnO, further fully eliminating PSCs hysteresis; (iii) the modification makes ZnO compatible with perovskite, nicely resolving the instability of ZnO/perovskite interface. With all these findings, PSCs with the best efficiency up to 21.1% and no hysteresis are successfully fabricated. PSCs stable in air for more than 300 h are achieved when graphene is used to further encapsulate the cells.

Surface passivation of ZnO by a thin layer of MgO and protonated ethanolamine readily makes ZnO a very promising electron-transporting material for creating efficient, hysteresis-free and stable perovskite solar cells (PSCs). PSCs, stable in air for more than 300 h, are achieved when graphene is used to encapsulate the cells.

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has now exceeded 20%; thus, research focus has shifted to establishing the foundations for commercialization. One of the pivotal themes is to curtail the overall fabrication time, to reduce unit cost, and mass-produce PSCs. Additionally, energy dissipation during the thermal annealing (TA) stage must be minimized by realizing a genuine low-temperature (LT) process. Here, tin oxide (SnO₂) thin films (TFs) are formulated at extremely high speed, within 5 min, under an almost room-temperature environment (<50 °C), using atmospheric Ar/O₂ plasma energy (P-SnO₂) and are applied as an electron transport layer of a “n–i–p”-type planar PSC. Compared with a thermally annealed SnO₂ TF (T-SnO₂), the P-SnO₂ TF yields a more even surface but also outstanding electrical conductivity with higher electron mobility and a lower number of charge trap sites, consequently achieving a superior PCE of 19.56% in P-SnO₂-based PSCs. These findings motivate the use of a plasma strategy to fabricate various metal oxide TFs using the sol–gel route.

A tin oxide (SnO₂) electron transport layer for a perovskite solar cell is successfully fabricated at extremely high speeds at a genuinely low temperature using atmospheric Ar/O₂ plasma annealing. This plasma-annealed SnO₂ (P-SnO₂) exhibits outstanding electrical conductivity and charge-extraction ability compared to thermally-annealed SnO₂, consequently achieving a superior PCE of 19.56% in P-SnO₂-based PSCs.

High performance perovskite solar cells based on CH₃NH₃PbI₃ with power conversion efficiency up to 17.04% (0.04 cm²) and 13.27% (4 cm²) were demonstrated via scalable near unity material utilization ratio one-step inkjet printing method with innovative vacuum-assisted thermal-annealing post-treatment and optimized solvent compositon. The most efficient inkjet-printed perovskite solar cell is reported here.

The development of inkjet printed electrodes based on copper nanoparticle grid combined with PEDOT:PSS is presented, for cost effective ITO-free solution processed organic photovoltaics.

Solution-processed and low-temperature Sn-rich perovskites show their low bandgap of about 1.2 eV, enabling potential applications in next-generation cost-effective ultraviolet (UV)–visible (vis)–near infrared (NIR) photodetection. Particularly, the crystallization (crystallinity and orientation) and film (smooth and dense film) properties of Sn-rich perovskites are critical for efficient photodetectors, but are limitedly studied. Here, controllable crystallization for growing high-quality films with the improvements of increased crystallinity and strengthened preferred orientation through a introducing rubidium cation into the methylammonium Sn-Pb perovskite system (65% Sn) is achieved. Fundamentally, the theoretical results show that rubidium incorporation causes lower surface energy of (110) plane, facilitating growth in the dominating plane and suppressing growth of other competing planes. Consequently, the methylammonium-rubidium Sn-Pb perovskite photodetectors simultaneously achieve larger photocurrent and lower noise current. Finally, highly efficient UV–vis–NIR (300–1100 nm) photodetectors with record-high linear dynamic range of 110 and 3 dB cut-off frequency reaching 1 MHz are demonstrated. This work contributes to enriching the cation selection in Sn-Pb perovskite systems and offering a promising candidate for low-cost UV–vis–NIR photodetection.

Controllable crystallization for growing high-quality films with increased crystallinity and strengthened preferred orientation is achieved through introducing rubidium cation into the methylammonium Sn-Pb perovskite system. Methylammonium-rubidium Sn-rich perovskite-photodetectors simultaneously achieve larger photocurrent and lower noise current. Highly efficient UV–vis-near infrared (300–1100 nm) photodetectors with record-high linear dynamic range of 110 and 3 dB cut-off frequency reaching 1 MHz are demonstrated.

Methoxybenzene (PhOMe) green anti-solvent is used to obtain perovskites with superior quality. The best power conversion efficiency for perovskite solar cells prepared by PhOMe anti-solvent reaches 19.42% with a stabilized PCE of 19.08%. The results clearly show that PhOMe possesses great practical significance for developing high-efficiency perovskite-based photovoltaic devices and other optoelectronic devices through an environment-friendly manufacturing process.

The sensitivity of organic–inorganic perovskites to environmental factors remains a major barrier for these materials to become commercially viable for photovoltaic applications. In this work, the degradation of formamidinium lead iodide (FAPbI₃) perovskite in a moist environment is systematically investigated. It is shown that the level of relative humidity (RH) is important for the onset of degradation processes. Below 30% RH, the black phase of the FAPbI₃ perovskite shows excellent phase stability over 90 d. Once the RH reaches 50%, degradation of the FAPbI₃ perovskite occurs rapidly. Results from a Kelvin probe force microscopy study reveal that the formation of nonperovskite phases initiates at the grain boundaries and the phase transition proceeds toward the grain interiors. Also, ion migration along the grain boundaries is greatly enhanced upon degradation. A post-thermal treatment (PTT) that removes chemical residues at the grain boundaries which effectively slows the degradation process is developed. Finally, it is demonstrated that the PTT process improves the performance and stability of the final device.

Moisture-induced degradation of FAPbI₃ perovskite is systematically investigated. A Kelvin probe force microscopy study reveals that the formation of nonperovskite phases initiates at the grain boundaries and the phase transition proceeds toward the grain interiors. A post-thermal treatment that removes chemical residues at the grain boundaries which effectively slows the degradation process is developed.

Organic–inorganic perovskites have demonstrated an impressive potential for the design of the next generation of solar cells. Perovskite solar cells (PSCs) are currently considered for scaling up and commercialization. Many of the lab-scale preparation methods are however difficult to scale up or are environmentally unfriendly. The highest efficient PSCs are currently prepared using the antisolvent method, which utilizes a significant amount of an organic solvent to induce perovskite crystallization in a thin film. An antisolvent-free method is developed in this work using flash infrared annealing (FIRA) to prepare methylammonium lead iodide (MAPbI₃) PSCs with a record stabilized power conversion efficiency of 18.3%. With an irradiation time of fewer than 2 s, FIRA enables the coating of glass and plastic substrates with pinhole-free perovskite films that exhibit micrometer-size crystalline domains. This work discusses the FIRA-induced crystallization mechanism and unveils the main parameters controlling the film morphology. The replacement of the antisolvent method and the larger crystalline domains resulting from flash annealing make FIRA a highly promising method for the scale-up of PSC manufacture.

Flash infrared annealing (FIRA) is demonstrated as an antisolvent-free method to prepare methylammonium lead iodide perovskite solar cells with over 18% efficiency. FIRA enables the preparation of pinhole-free perovskite films with micrometer-size crystalline domains over a large area of both glass and plastic substrates. FIRA, as a rapid and environmentally friendly method to scale up perovskite solar cells is proposed.