Power Conversion Efficiency Of Device Research Articles

Spontaneously spreading film process to improve the photovoltaic performance of organic solar cells with PHJ structure.

Efficient charge transport and extraction within the active layer plays a major role in the photovoltaic performance of organic solar cells (OSCs). In this work, the spontaneously spreading (SS) process was utilized to achieve sequential deposition of the active layer with a planar heterojunction (PHJ) structure. The SS process avoids the damage of the upper layer solution to the lower layer film by the spin coating process. The film with PHJ structure exhibits notable vertical phase separation compared to the bulk heterojunction (BHJ). Moreover, the power conversion efficiency (PCE) of the PHJ device (12.00%) is significantly higher than that of the BHJ (10.84%) due to the efficient charge transport. This work offers a novel fabrication method and device structure to enhance the photovoltaic performance of OSCs.

A polymer library enables the rapid identification of a highly scalable and efficient donor material for organic solar cells.

The dramatic improvement of the PCE (power conversion efficiency) of organic photovoltaic devices in the past few years has been driven by the development of new polymer donor materials and non-fullerene acceptors (NFAs). In the design of such materials synthetic scalability is often not considered, and hence complicated synthetic protocols are typical for high-performing materials. Here we report an approach to readily introduce a variety of solubilizing groups into a benzo[c][1,2,5]thiadiazole acceptor comonomer. This allowed for the ready preparation of a library of eleven donor polymers of varying side chains and comonomers, which facilitated a rapid screening of properties and photovoltaic device performance. Donor FO6-T emerged as the optimal material, exhibiting good solubility in chlorinated and non-chlorinated solvents and achieving 15.4% PCE with L8BO as the acceptor (15.2% with Y6) and good device stability. FO6-T was readily prepared on the gram scale, and synthetic complexity (SC) analysis highlighted FO6-T as an attractive donor polymer for potential large scale applications.

Boosting radiation of stacked halide layer for perovskite solar cells with efficiency over 25%

<h2>Summary</h2> Although halide perovskite solar cells (PSCs) have shown tremendous progress in device performance, state-of-the-art PSCs are still far below the theoretical efficiency. To further reach the theoretical limit, it is essentially required to maximize radiative recombination in the full device stack. Here, we report that boosting radiation in the full device stack is an effective way for reaching the radiative limit of power conversion efficiency (PCE) by demonstrating the correlation between external photoluminescence quantum efficiency (PLQE) of the full device stack and PCE of the devices. We found that controlling the bottom charge transporting layer (CTL)/perovskite interface is a main factor to boost radiation in the full device stack. The device combined with the interface and bulk engineering exhibited an improved external PLQE of 15.57%, resulting in an improved PCE of over 25% (certified 25.06%) and almost 95% achievement rate of the radiative limit open-circuit voltage (<i>V</i>_oc).

Benzodithiophene unit copolymerization to improve the stability of thiophene-based organic solar cells

With the increasing performance of organic solar cells (OSCs), the design of stable donor materials is of paramount importance. In this work, we synthesised a simple alternating copolymer with thiophene and BDT (P3T-BDT) units to understand the impact of incorporation of BDT on the thermal stability of the commonly used thiophene-based OSCs. OSCs fabricated with P3T-BDT:PC71BM and P3HT:PC71BM with 1:4 ratios displayed a different degradation kinetics despite their similar initial power conversion efficiency (PCE). The PCE of P3HT-based device degraded by half while the P3T-BDT-based device lost only 15% of its initial PCE after thermally being degraded at 85 ∘C for 48 h mainly due to the decrease in J . Thermally-induced degradation of P3HT caused chain breakage while the P3T-BDT remained intact. The surface morphology of P3HT:PC71BM film exhibited a large increase in roughness in the first few hours leading to a loss of more 40% of its initial PCE while the P3T-BDT based OSC had a similar roughness throughout the accelerated ageing. This is also confirmed by the growth of the PL intensity of P3HT:PC71BM while P3T-BDT:PC71BM remained the same confirming a suppression of demixing of the donor and acceptor in the latter. In summary, the addition a BDT unit in the thiophene-based homopolymer was found to improve the thermal stability thiophene-based OSCs.

Linear pseudo-halogen anion passivating defects for MAPbI3 perovskite solar cells

The development of perovskite solar cells has improved rapidly. However, PSCs generally suffer from instability, due to the detrimental defects. Additive engineering is a favorable method for defect passivation. In this work, the linear pseudo-halogen salt, KSCN, is introduced into the MAPbI3 perovskite film to improve the performance of PSC. The trap density of cells with SCN− is decreased significantly. The SCN− not only can fill halogen vacancies to reduce the halide-related defects, but also can interact with the uncoordinated Pb2+ via coordinate bond to stabilize perovskite lattice structure. Moreover, the performance of devices with other linear pseudo-halogen anions (OCN−, SeCN−) are also investigated. Due to the improved short circuit current density, the power conversion efficiency of devices increases from 18.02% (PVK) to 20.41% (PVK–SCN-), 19.53% (PVK–OCN-) and 19.23% (PVK–SeCN-), respectively. After introducing pseudo-halide anions, the devices showed robust stability under the ambient environment.

Systematic Investigation of Core and Endcap Selection on the Development of Functional π-Conjugated Materials

We investigate the optoelectronic properties of four new π-conjugated materials, which feature either a 3,4-ethylenedioxythiophene (EDOT) or an EDOT-flanked benzothiadiazole aryl core with two N-annulated perylene diimide (NPDI) or theobromine endcaps. Endcap selection was an important factor for the preferred molecular geometry, where the use of NPDI endcaps induced a dragonfly-type conformation and the use of theobromine endcaps promoted a corkscrew-like conformation. Electrochemically, the choice of aryl π-conjugated core was found to have a strong influence on the molecule’s highest occupied molecular orbital (HOMO) energy level, while the choice of endcap had a more profound effect on the lowest unoccupied molecular orbital (LUMO) energy level. Although the optical absorption profiles were generally dominated by endcap contributions, using the larger EDOT-flanked benzothiadiazole aryl core was found to decrease the optical energy band gap. Proof-of-concept organic photovoltaic (OPV) devices, using a PM6:Y6 bulk heterojunction (BHJ) photoactive layer, were fabricated using the four new π-conjugated materials as the cathode interlayer (CIL). The molecules featuring the EDOT aryl core (A and B) enabled OPV device power conversion efficiencies (PCEs) by around 12%, comparable to control devices using PDINN as the CIL, while those featuring the EDOT-flanked benzothiadiazole aryl core (C and D) obtained PCEs of 10.5%. The observed differences in OPV device performance were attributed to superior solubility and subsequent CIL film formation in the case of A and B, compared to C and D, which, in turn, led to improved contact between the Ag top electrode and the BHJ photoactive layer.

Fibrillization of Non-Fullerene Acceptors Enables 19% Efficiency Pseudo-Bulk Heterojunction Organic Solar Cells.

The structural order and aggregation of non-fullerene acceptors (NFA) are critical toward light absorption, phase separation, and charge transport properties of their photovoltaic blends with electron donors, and determine the power conversion efficiency (PCE) of the corresponding organic solar cells (OSCs). In this work, the fibrillization of small molecular NFA L8-BO with the assistance of fused-ring solvent additive 1-fluoronaphthalene (FN) to substantially improve device PCE is demonstrated. Molecular dynamics simulations show that FN attaches to the backbone of L8-BO as the molecular bridge to enhance the intermolecular packing , inducing 1D self-assembly of L8-BO into fine fibrils with a compact polycrystal structure. The L8-BO fibrils are incorporated into a pseudo-bulk heterojunction (P-BHJ) active layer with D18 as a donor, and show enhanced light absorption, charge transport, and collection properties, leading to enhanced PCE from 16.0% to an unprecedented 19.0% in the D18/L8-BO binary P-BHJ OSC, featuring a high fill factor of 80%. This work demonstrates a strategy for fibrillating NFAs toward the enhanced performance of OSCs.

Boosting Perovskite Solar Cells Efficiency and Stability: Interfacial Passivation of Crosslinked Fullerene Eliminates the "Burn-in" Decay.

Perovskite solar cells (PSCs) longevity is nowadays the bottleneck for their full commercial exploitation. Although lot of research is ongoing, the initial decay of the output power - an effect known as "burn-in" degradation happening in the first 100h - is still unavoidable, significantly reducing the overall performance (typically of >20%). In this paper, the origin of the "burn-in" degradation in n-i-p type PSCs is demonstrated that is directly related to Li+ ions migration coming from the SnO2 electron transporting layer visualized by time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurements. To block the ion movement, a thin cross-linked [6,6]-phenyl-C61-butyric acid methyl ester layer on top of the SnO2 layer is introduced, resulting in Li+ immobilization. This results in the elimination of the "burn-in" degradation, showing for the first time a zero "burn-in" loss in the performances while boosting device power conversion efficiency to >22% for triple-cation-based PSCs and >24% for formamidinium-based (FAPbI3 ) PSCs, proving the general validity of this approach and creating a new framework for the realization of stable PSCs devices.

Influence of Block Ratio on Thermal, Optical, and Photovoltaic Properties of Poly(3-hexylthiophene)-b-poly(3-butylthiophene)-b-poly(3-octylthiophene)

Efforts to improve the solar power conversion efficiencies of binary bulk heterojunction-type organic photovoltaic devices using an active layer consisting of a poly-(3-alkylthiophene) (P3AT) homopolymer and a suitable fullerene derivative face barriers caused by the intrinsic properties of homopolymers. To overcome such barriers, researchers might be able to chemically tailor homopolymers by means of monomer ratio-balanced block copolymerization to obtain preferable properties. Triblock copolymers consisting of three components-3-hexylthiophene (HT), 3-butylthiophene (BT), and 3-octylthiophene (OT)-were synthesized via Grignard metathesis (GRIM) polymerization. The component ratios of the synthesized block copolymers were virtually the same as the feeding ratios of the monomers, a fact which was verified using 1H-NMR spectra. All the copolymers exhibited comparable crystalline and melting temperatures, which increased when one type of monomer became dominant. In addition, their power conversion efficiencies and photoluminescence properties were governed by the major components of the copolymers. Interestingly, the HT component-dominated block copolymer indicated the highest power conversion efficiency, comparable to that of its homopolymer, although its molecular weight was significantly shorter.

Understanding the efficiency enhancement of perovskite solar cells with NaGdF4: Er3+/Yb3+ nanorods

Perovskite solar cells have drawn significant attention due to their excellent photovoltaic characteristics. Upconversion luminescence material modification is a good strategy to extend the device response to the near-infrared region, which can further increase device efficiency. By adding NaGdF 4 :Er 3+ /Yb 3+ nanorods into chlorobenzene as an additive in the antisolvent to modify the perovskite layer, we found that upconversion luminescence nanoparticles can effectively improve the perovskite solar cell performance. However, unexpectedly, the photocurrent contributed by the infrared part is lower. The efficiency increase of perovskite solar cells is contributed by defect passivation. Further research shows that nanoparticles can effectively fill the holes and gaps at the grain boundaries, eliminate surface defects of the perovskite, and modify the perovskite film, which reduces carrier recombination and effectively improves the device's performance. Finally, the power conversion efficiency of the champion device can reach 21.1%. This research demonstrates the function of upconversion luminescence nanoparticles in PSCs and provides a simple way to improve the device's efficiency. • The up-conversion luminescence NaGdF 4 :Er 3+ /Yb 3+ is introduced into the perovskite layer via anti-solvent chlorobenzene. • The champion device achieved an efficiency of 21.1% by passivating perovskite grain defects through NaGdF 4 nanocrystals. • The reason for the efficiency enhancement is the increase of carrier lifetime rather than spectrum broadening to infrared field.

Amidine thiourea as a multifunctional modifier of buried interface for effective perovskite solar cells with reduced lead leakage

The defects at buried SnO 2 /perovskite interface can influence the performances of perovskite solar cells by causing the poor perovskite crystallinity, bad interface connection, undesired interfacial recombination and electron transfer efficiency. Now, multifunctional amidine thiourea is used to modify the buried SnO 2 /perovskite interface. The amidine thiourea can passivate the interface defects by the electron donation roles of N and S atoms, improve the electron transfer efficiency by enhancing the interface connection and regulating the interface energy level matching, reduce lead leakage and reinforce the structural stability of device by the coordination and hydrogen bond interaction. The perovskite solar cells with the amidine thiourea modification exhibit an enhanced power conversion efficiency (20.48%) and stability, outperforming than that of control device (18.65%). Modifying the buried interface with small organic molecule is a feasible and efficient method to improve the performances of PSCs. The amidine thiourea interface chemical bridge can accelerate the interface charge extraction by realizing the tight connection and regulating the energy level matching of SnO 2 /perovskite interface. Besides, amidine thiourea can passivate the oxygen vacancy defects on SnO 2 and the uncoordinated Pb defects on perovskite. In addition, the strong chemical interaction between ADT and Pb can reduce the lead leakage in device. After modifying the SnO 2 /perovskite interface with amidine thiourea, the power conversion efficiency and stability of device are all improved. • Amidine thiourea (ADT) is used to modify the buried SnO 2 /perovskite interface. • ADT can passivate the buried oxygen vacancy defects and uncoordinated Pb 2+ defect. • ADT can enhance connection and regulate energy level matching at buried interface. • ADT can reduce lead leakage through strong chemical interactions. • ADT-modified devices exhibit enhanced power conversion efficiency and stability.

Intermediate-phase engineering via dimethylammonium cation additive for stable perovskite solar cells.

Achieving the long-term stability of perovskite solar cells is arguably the most important challenge required to enable widespread commercialization. Understanding the perovskite crystallization process and its direct impact on device stability is critical to achieving this goal. The commonly employed dimethyl-formamide/dimethyl-sulfoxide solvent preparation method results in a poor crystal quality and microstructure of the polycrystalline perovskite films. In this work, we introduce a high-temperature dimethyl-sulfoxide-free processing method that utilizes dimethylammonium chloride as an additive to control the perovskite intermediate precursor phases. By controlling the crystallization sequence, we tune the grain size, texturing, orientation (corner-up versus face-up) and crystallinity of the formamidinium (FA)/caesium (FA)yCs1-yPb(IxBr1-x)3 perovskite system. A population of encapsulated devices showed improved operational stability, with a median T80 lifetime (the time over which the device power conversion efficiency decreases to 80% of its initial value) for the steady-state power conversion efficiency of 1,190 hours, and a champion device showed a T80 of 1,410 hours, under simulated sunlight at 65 °C in air, under open-circuit conditions. This work highlights the importance of material quality in achieving the long-term operational stability of perovskite optoelectronic devices.

A Self‐Assembled Vertical‐Gradient and Well‐Dispersed MXene Structure for Flexible Large‐Area Perovskite Modules

AbstractAdvancing hole transport layers (HTL) to realize large‐area, flexible, and high‐performance perovskite solar cells (PSCs) is one of the most challenging issues for its commercialization. Here, a self‐assembled gradient Ti3C2Tx MXene incorporated PEDOT:PSS HTL is demonstrated to achieve high‐performance large‐area PSCs by establishing half‐caramelization‐based glucose‐induced MXene redistribution. Through this process, the Ti3C2Tx MXene nanosheets are spontaneously dispersed and redistributed at the top region of HTL to form the unique gradient distribution structure composed of MXene:Glucose:PEDOT:PSS (MG‐PEDOT). These results show that the MG‐PEDOT HTL not only offers favorable energy level alignment and efficient charge extraction, but also improves the film quality of perovskite layer featuring enlarged grain size, lower trap density, and longer carrier lifetime. Consequently, the power conversion efficiency (PCE) of the flexible device based on MG‐PEDOT HTL is increased by 36% compared to that of pristine PEDOT:PSS HTL. Meanwhile, the flexible perovskite solar minimodule (15 cm2 area) using MG‐PEDOT HTL achieve a PCE of 17.06%. The encapsulated modules show remarkable long‐term storage stability at 85 °C in ambient air (≈90% efficiency retention after 1200 h) and enhanced operational lifetime (≈90% efficiency retention after 200 h). This new approach shows a promising future of the self‐assembled HTLs for developing optoelectronic devices.

Ecofriendly Hydroxyalkyl Cellulose Additives for Efficient and Stable MAPbI3‐Based Inverted Perovskite Solar Cells

Perovskite solar cells (PSCs) have been demonstrated to be one of the most promising technologies in the field of renewable energy. However, the presence of the defects in the perovskite films greatly limits the efficiency and the stability of the PSCs. The additive engineering is one of the most effective approaches to overcome this problem. Most of the successful additives are extracted from the petroleum‐based materials, while the research on the biomass‐based additives is still lagging behind. In this paper, two ecofriendly hydroxyalkyl cellulose additives, i.e., hydroxyethyl cellulose (HEC) and hydroxylpropyl cellulose (HPC), are investigated on the performance of the MAPbI3‐based inverted PSCs. Due to the strong interaction between the hydroxyl groups of the cellulose and the divalent cations of the perovskite, these additives enhance the crystal grain orientation and significantly repair the defects of the perovskite films. Working as the additives, these two cellulose derivatives show a strong passivation ability, which significantly reduces the trap density and improves the optoelectronic feature of the PSCs. Compared with the average power conversion efficiency (PCE) of the control device (19.19%), an enhancement of ~10% is achieved after the addition of HEC. The optimized device (PCE = 21.25%) with a long‐term stability (10:80 h, PCE = 20.93%) is achieved by the incorporation of the HEC additives into the precursor solution. It is the best performance among the PSCs with the cellulose additives up to now. This research provides a novel choice to develop a cost‐effective and renewable additive for the PSCs with high efficiency and excellent long‐term stability.

20.67%-Efficiency Inorganic CsPbI3 Solar Cells Enabled by Zwitterion Ion Interface Treatment.

All-inorganic CsPbI3 perovskite solar cells (PSCs) have been extensively studied due to their high thermal stability and unprecedented rise in power conversion efficiency (PCE). Recently, the champion PCE of CsPbI3 PSCs has reached up to 21%; however, it is still much lower than that of organic-inorganic hybrid PSCs. Interface modification to passivate surface defects and minimize charge recombination and trapping is important to further improve the efficiency of CsPbI3 PSCs. Herein, a new zwitterion ion is deposited at the interface between electron transporting layer (ETL) and perovskite layer to passivate the defects therein. The zwitterion ions can not only passivate oxygen vacancy (VO ) and iodine vacancy (VI ) defects, but also improve the band alignment at the ETL-perovskite interface. After the interface treatment, the PCE of CsPbI3 device reaches up to 20.67%, which is among the highest values of CsPbI3 PSCs so far. Due to the defect passivation and hydrophobicity improvement, the PCE of optimized device remains 94% of its original value after 800h storing under ambient condition. These results provide an efficient way to improve the quality of ETL-perovskite interface by zwitterion ions for achieving high performance inorganic CsPbI3 PSCs.

Improved Power Conversion Efficiency with Tunable Electronic Structures of the Cation-Engineered [Ai]PbI3 Perovskites for Solar Cells: First-Principles Calculations.

Higher power conversion efficiencies for photovoltaic devices can be achieved through simple and low production cost processing of APbI3(A=CH3NH3,CHN2H4,…) perovskites. Due to their limited long-term stability, however, there is an urgent need to find alternative structural combinations for this family of materials. In this study, we propose to investigate the prospects of cation-substitution within the A-site of the APbI3 perovskite by selecting nine substituting organic and inorganic cations to enhance the stability of the material. The tolerance and the octahedral factors are calculated and reported as two of the most critical geometrical features, in order to assess which perovskite compounds can be experimentally designed. Our results showed an improvement in the thermal stability of the organic cation substitutions in contrast to the inorganic cations, with an increase in the power conversion efficiency of the Hydroxyl-ammonium (NH3OH) substitute to η = 25.84%.

Highly transmitted silver nanowires-SWCNTs conductive flexible film by nested density structure and aluminum-doped zinc oxide capping layer for flexible amorphous silicon solar cells

• Ag NWs-SWCNTs (AS) composites with high and sparse density networks were fabricated by ultrasonic. • The AS/AZO (ASA) bilayer showed superior transmittance (92%@550 nm), mechanicity, stability, and adhesion. • The film demonstrates high stability with a ΔR/R 0 = 10% after 10,000 bending times, boiling, taping, and CO 2 plasma. • The power conversion efficiency of photovoltaic devices with flexible ASA TCFs was increased by 26%. • No significant reduction in power conversion efficiency was observed even after bending for 3000 times. Indium tin oxide (ITO) is widely used in transparent conductive films (TCFs); however, several disadvantages, such as high cost and toxicity of indium, limit its applications. Therefore, it is necessary to develop other materials that can replace ITO. Silver nanowires or single walled carbon nanotubes (SWCNTs) have attracted considerable interest owing to their unique electrical, optical, and thermal stabilities, and thus, they are ideal for transparent electrodes for flexible or stretchable devices. In this study, we develop a novel architecture of composite TCFs on a polyethylene naphthalate (PEN) flexible substrate. Herein, the silver nanowires-SWCNTs films with nested density structure were fabricated through ultrasonic spraying technology by varying the spraying width. For achieving enhanced transmittance, we combined the larger irregular grids and holes with fewer nanowires stacked in the longitudinal direction, more optical channels, and good carrier transport. Thereafter, aluminum-doped zinc oxide (AZO) was used as capping to the structure for enhancing the optical properties of the TCFs. The silver nanowires-SWCNTs/AZO (ASA) bilayer was obtained in the optimized architecture, which showed superior optoelectronic performance to that shown by commercial ITO with a high optical transmittance of 92% at the wavelength of 550 nm and low sheet resistance of 17 Ω/sq. In the specially structured conductive film, the significant improvement in the transmittance and uniformity of the sheet resistance was attributed to the effective nanowire junction contact compared to that in ordinary structure of silver nanowires, which reduced the mean density of small clusters of nanowires. Compared with the silver nanowires-SWCNTs films, the ASA bilayer film exhibited excellent resistance to boiling, mechanical bending (10,000 cycles), and CO 2 plasma. Moreover, the sheet resistance of ASA changed slightly after the tape tests, thereby illustrating a strong adhesion to the PEN substrate after the enclosure of AZO. Meanwhile, the AZO capping layer can enhance the optical transmittance between 600 and 1500 nm. In addition, the amorphous silicon photovoltaic devices with flexible ASA TCFs exhibited a power conversion efficiency (PCE) of 8.67%. After bending for 3000 times, the PCE was decreased to 8.20%, thereby demonstrating the potential of developed films to replace traditional ITO.

Synergistic dual-interface modification strategy for highly reproducible and efficient PTAA-based inverted perovskite solar cells

Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA)-based inverted perovskite solar cells (PSCs) are the most efficient device type reported to date. Nevertheless, the high hydrophobicity of PTAA and the nonradiative recombination loss significantly limit the repeatability and the performances of these devices. In this study, polyvinyl oxide (PEO) and tetra-n-propylammonium bromide (TPAB) were introduced to overcome the hydrophobicity of PTAA and the anode and cathode interface nonradiative recombination losses through the synergistic effect of these materials. The results showed that the PEO could dramatically improve the wetting properties of the perovskite precursor on the PTAA surface, correspondingly enhancing the microstructure of the film, eliminating the defects, and enhancing the anode interfacial contact of the device. The performances and performance repeatability of the devices were greatly improved. The ratio of the short-circuited devices decreased from 44.23 % to 0 %, and the average power conversion efficiency (PCE) increased dramatically. In addition, a facile TPAB surface treatment strategy was proposed to reduce the potential threat of PEO introduction to the device stability as well as improve the cathode interface contact problems of the device. Owing to the synergistic effect of the PEO and TPAB, the performance and stability were both enhanced. The highest PCE of 21.62 % was achieved, and the average PCE of TPAB devices could be maintained at 80 % for 298 h (in air, 23 °C, 25 RH%) and 96 % for 217 d (in N2, 23 °C) of the initial PCE value. The synergistic dual-interface modification strategy proposed in this paper lights the way for the preparation of highly reproducible, efficient, and stable PTAA-based inverted perovskite solar cells.

Improving the Performance of Invert Perovskite Solar Cell Devices By a Multifunctional Ammonium Salt

In past years, halide perovskite solar cells (PSCs) have attracted much attention and are considered as the next-generation solar cells due to their excellent performance. Compared to the conventional structure, the inverted perovskite solar cell device has great potential in large-scale practical applications due to the low-temperature manufacturing process. However, the power conversion efficiency (PCE) is still lower than conventional structure devices, which is because of the high trap density in the surface and grain boundary of perovskite film. One kind of defect is the iodine vacancy caused by methylammonium iodide (MAI) volatilization during perovskite film annealing. I- could be oxidized into I2 and then volatilize out during the perovskite film annealing, the vacancy of I- could form trap states in the surface and grain boundary of the perovskite film. The surface traps induce many defects and increase the charge recombination rate in the inverted polycrystalline perovskite film, which causes PCE loss in the devices. Although lots of efforts are to improve the PCE of devices, perovskite solar cell device is still hard to practical applicate due to poor stability under light exposure conditions. Under light soaking especially UV light, perovskite film would degrade which means I3 - easily change to I2 and induce the lattice defects of perovskite film, which further influence the performance of PSCs. Herein, we present a strategy to suppress the I2 generation to decrease the trap density, reduce the charge recombination in perovskite film and further improve the performance of devices by an ammonium salt named tetrabutylammonium chloride (TBACl) modified. The PCE of devices increase from 18.52% to 20.36% after TBACl was modified, and TBACl also reduce the Voc loss in the perovskite solar cell devices. Furthermore, TBACl passivation enhances the light stability of devices and slows down PSCs degradation with UV light soaking. Because TBACl distributes in the surface and GBs of perovskite film that could absorb the UV light and decrease the effects on the perovskite layer. Benefiting from the influence of TBACl on perovskite solar cell devices, the devices could maintain over 90% with light soaking 120 h and UV light irradiation 450 min, respectively. However, the control devices only could maintain ~47% and ~51% of the initial PCE values under light exposure and UV light soaking conditions, respectively. Thus, we provide a low-cost, easy, and effective post-treatment strategy to enhance the device performance and improve the light stability of perovskite solar cell devices.

Photovoltaic Performance Improvement of All‐Inorganic CsPbBr3 Perovskite Solar Cells by Antisolvent Assisted Crystallization

AbstractAll‐inorganic CsPbBr3 perovskite solar cells (PSCs) are expected to form semitransparent or top‐cell of tandem solar cells with Cu(In,Ga)Se2 or crystalline silicon solar cells owing to their outstanding environmental tolerance and wide bandgap. However, the commonly solution‐processed CsPbBr3 perovskite films usually suffer from inferior film quality. Herein, we propose antisolvent assisted crystallization method to prepare CsPbBr3 films by multi‐step spin‐coating process. During the spin‐coating step, the underlying PbBr2 layer is treated with anisole antisolvent in different amount of 0, 50, 100, 150, and 200 μl, respectively, and heated at 80 °C for 30 min. Thus, CsPbBr3 films with high crystallinity, less grain boundaries and good coverage are prepared. The champion power conversion efficiency (PCE) of devices based on antisolvent treatment reaches 6.5 %, compared to that of devices without antisolvent treatment (PCE 4.97 %). Moreover, the devices treated with antisolvent without encapsulation exhibit good stability under ambient conditions. The antisolvent assisted crystallization provides an effective route for improving the quality of CsPbBr3 films and promotes the commercialization of all‐inorganic CsPbBr3 PSCs.