Stability Assessment of p i n Perovskite Photovoltaic Mini Modules Utilizing Different Top Metal Electrodes

Long term stability is one of the major challenges for p i n type perovskite solar modules PSMs . Here, we demonstrate the fabrication of fully laser patterned series interconnected p i n perovskite mini modules, in which either single Cu or Ag layers are compared with Cu Au metal bilayer top electrodes. According to the scanning electron microscopy measurements, we found that Cu or Ag top electrodes often exhibit flaking of the metal upon P3 top contact removal laser patterning. For Cu Au bilayer top electrodes, metal flaking may cause intermittent short circuits between interconnected sub cells during operation, resulting in fluctuations in the maximum power point MPP . Here, we demonstrate Cu Au metal bilayer based PSMs with an efficiency of 18.9 on an active area of 2.2 cm2 under continuous 1 sun illumination. This work highlights the importance of optimizing the top contact composition to tackle the operational stability of mini modules, and could help to improve the feasibility of large area module deployment for the commercialization of perovskite photovoltaic

The challenge of studying perovskite solar cells stability with machine learning

Perovskite solar cells are the most dynamic emerging photovoltaic technology and attracts the attention of thousands of researchers worldwide. Recently, many of them are targeting device stability issues the key challenge for this technology which has resulted in the accumulation of a significant amount of data. The best example is the Perovskite Database Project, which also includes stability related metrics. From this database, we use data on 1,800 perovskite solar cells where device stability is reported and use Random Forest to identify and study the most important factors for cell stability. By applying the concept of learning curves, we find that the potential for improving the models performance by adding more data of the same quality is limited. However, a significant improvement can be made by increasing data quality by reporting more complete information on the performed experiments. Furthermore, we study an in house database with data on more than 1,000 solar cells, where the entire aging curve for each cell is available as opposed to stability metrics based on a single number. We show that the interpretation of aging experiments can strongly depend on the chosen stability metric, unnaturally favoring some cells over others. Therefore, choosing universal stability metrics is a critical question for future databases targeting this promising technolog

Encapsulation and outdoor testing of Perovskite Solar Cells comparing industrially relevant process with a simplified lab procedure

Perovskite solar cells PSCs have shown great potential for next generation photovoltaics. One of the main barriers to their commercial use is their poor long term stability under ambient conditions and, in particular, their sensitivity to moisture and oxygen. Therefore, several encapsulation strategies are being developed in an attempt to improve the stability of PSCs in a humid environment. The lack of common testing procedures makes the comparison of encapsulation strategies challenging. In this paper, we optimized and investigated two common encapsulation strategies lamination based glass glass encapsulation for outdoor operation and commercial use COM and a simple glue based encapsulation mostly utilized for laboratory research purposes LAB . We compare both approaches and evaluate their effectiveness to impede humidity ingress under three different testing conditions on shelf storage at 21 C and 30 relative humidity RH ISOS D1 , damp heat exposure at 85 C and 85 RH ISOS D3 , and outdoor operational stability continuously monitoring device performance for 10 months under maximum power point tracking on a roof top test site in Berlin, Germany ISOS O3 . LAB encapsulation of perovskite devices consists of glue and a cover glass and can be performed at ambient temperature, in an inert environment without the need for complex equipment. This glue based encapsulation procedure allowed PSCs to retain more than 93 of their conversion efficiency after 1566 h of storage in ambient atmosphere and, therefore, is sufficient and suitable as an interim encapsulation for cell transport or short term experiments outside an inert atmosphere. However, this simple encapsulation does not pass the IEC 61215 damp heat test and hence results in a high probability of fast degradation of the cells under outdoor conditions. The COM encapsulation procedure requires the use of a vacuum laminator and the cells to be able to withstand a short period of air exposure and at least 20 min at elevated temperatures in our case, 150 C . This encapsulation method enabled the cells to pass the IEC 61215 damp heat test and even to retain over 95 of their initial efficiency after 1566 h in a damp heat chamber. Above all, passing the damp heat test for COM encapsulated devices translates to devices fully retaining their initial efficiency for the full duration of the outdoor test gt;10 months . To the best of the authors knowledge, this is one of the longest outdoor stability demonstrations for PSCs published to date. We stress that both encapsulation approaches described in this work are useful for the scientific community as they fulfill different purposes the COM for the realization of prototypes for long term real condition validation and, ultimately, commercialization of perovskite solar cells and the LAB procedure to enable testing and carrying out experiments on perovskite solar cells under noninert condition

Laser based series interconnection of chalcopyrite und perovskite solar cells Analysis of material modifications and implications for achieving small dead area widths

Both nanosecond pulses and picosecond laser pulses are used for P2 patterning of chalcopyrite Cu In,Ga Se2, CIGSe and metal halide perovskite solar cell absorber layers. For CIGSe, the range of the modified material visualized by photoluminescence imaging is significantly wider than the actual physical linewidth, since energy input by the laser pulses leads to material modification in the vicinity of the scribed lines. This effect does not occur with the perovskite absorber layers, where there is no apparent influence on the edge regions. From numerical calculations of the temperature depth profiles and the surface temperature distributions it is concluded that this effect is due to the significantly lower perovskite absorber layer thickness compared to CIGSe and the nevertheless significantly higher laser fluence required for perovskite ablation. The unaffected edge regions around the P2 line in the perovskite enabled a reduction of the dead area width in the fabrication of 3 segmented mini modules, which could be significantly reduced from 430 to 230 m, while increasing the aperture area power conversion efficiency and also the geometric fill factor, which could be increased up to 94.

Textured interfaces in monolithic perovskite silicon tandem solar cells advanced light management for improved efficiency and energy yield

Efficient light management in monolithic perovskite silicon tandem solar cells is one of the prerequisites for achieving high power conversion efficiencies PCEs . Textured silicon wafers can be utilized for light management, however, this is typically not compatible with perovskite solution processing. Here, we instead employ a textured light management LM foil on the front side of a tandem solar cell processed on a wafer with planar front side and textured back side. This way the PCE of monolithic, 2 terminal perovskite silicon heterojunction tandem solar cells is significantly improved from 23.4 to 25.5 . Furthermore, we validate an advanced numerical model for our fabricated device and use it to optically optimize a number of device designs with textures at different interface with respect to the PCE and energy yield. These simulations predict a slightly lower optimal bandgap of the perovskite top cell in a textured device as compared to a flat one and demonstrate strong interdependency between the bandgap and the texture position in the monolithic stack. We estimate the PCE potential for the best performing both side textured device to be 32.5 for a perovskite bandgap of 1.66 eV. Furthermore, the results show that under perpendicular illumination conditions, for optimized designs, the LM foil on top of the cell performs only slightly better than a flat anti reflective coating. However, under diffuse illumination, the benefits of the LM foil are much greater. Finally, we calculate the energy yield for the different device designs, based on true weather data for three different locations throughout the year, taking direct as well as diffuse illumination fully into account. The results further confirm the benefits of front side texture, even more for BIPV applications. Overall, devices built on a both side textured silicon wafer perform best. However, we show that devices with textured LM foils on the cell s front side are a highly efficient alternativ

21.6 efficient Monolithic Perovskite Cu In,Ga Se2 Tandem Solar Cells with Thin Conformal Hole Transport Layers for Integration on Rough Bottom Cell Surfaces

Perovskite based tandem solar cells can increase the power conversion efficiency PCE of conventional single junction photovoltaic devices. Here, we present monolithic perovskite CIGSe tandem solar cells with a perovskite top cell fabricated directly on an as grown, rough CIGSe bottom cell. To prevent potential shunting due to the rough CIGSe surface, a thin NiOx layer is conformally deposited via atomic layer deposition on the front contact of the CIGSe bottom cell. The performance is further improved by an additional layer of the polymer PTAA at the NiOx perovskite interface. This hole transport bilayer enables a 21.6 stabilized PCE of the tandem device at amp; 8764;0.8 cm2 active area. We use TEM EDX measurements to investigate the deposition uniformity and conformality of the NiOx and PTAA layers. By absolute photoluminescence measurements, the contribution of the individual subcells to the tandem VOC is determined, revealing that further fine tuning of the recombination layers might improve the tandem VOC. Finally, on the basis of the obtained results, we give guidelines to improve monolithic perovskite CIGSe tandems toward predicted PCE estimates above 3

Modification by Ar and Kr Ion-Bombardment of Mo/Si X-Ray Multilayers

We have investigated the details of the growth of electron-beam deposited molybdenum and silicon layers and the effect of ion-beam bombardment on the morphology and interface smoothness of those layers. Using in-situ X-ray reflectivity, theta-2theta reflectivity scans, Auger Electron Spectroscopy (AES) and Transmission Electron Microscopy (TEM) we find that a reduction in both Mo and Si surface roughness can occur as a result of the ion-beam bombardment. However, the overall smoothing effect is limited by interface mixing at the underlying interface and it is also dependent on the deposition morphology for Mo layers. When depositing multilayers with 10 periods of 6 nm we find a large (factor 4) improvement of the reflectivity as a result of the ion-beam bombardment. Our best results, obtained by polishing all Si layers after growth with 300 eV Kr+ ions, give a roughness of 0.3 nm for the Mo-on-Si interfaces and less than 0.5 nm for Si-on-Mo interfaces. Cross-section TEM pictures confirm the observations qualitatively

Light-emission in reverse bias operation from poly(3- octylthiophene)-based light-emitting-diodes

We report light emission from light emitting diodes with poly(3‐octylthiophene) (P3OT) as the active layer in both forward and reverse bias operation. The onset of electroluminescence (EL) of ITO/P3OT/Al devices occurs at current densities of 6.25×10−4 A/cm2 in both modes of operation; both cases show identical EL spectra. For a P3OT thickness of 100 nm the onset of electroluminescence and current occurs at 3 V in the forward bias mode, and at about 18 V in the reverse mode of operation, at which a completely different voltage dependence of the current is observed. In the reverse mode of operation, the data suggest that carrier injection is a tunneling process through a triangular barrier of 0.4 eV at the metal–polymer interface. In the forward bias a Schottky‐like behavior is seen

Helianthos: Roll-to-Roll Deposition of Flexible Solar Cell Modules

In the development of the roll-to-roll deposition of amorphous silicon by means of plasma enhanced chemical vapor deposition, a number of different plasma aspects have been of importance. First, the understanding of process windows in terms of a dust free plasma has led to the formulation of an empirical scaling law for the dust free to dust forming transition in terms of the crucial process parameters such as, e.g., power and gas flows. Second, the homogeneity of deposition on an effective width of 30 cm has been demonstrated to be better than 5%. Increasing the deposition rate might be achieved by increasing the power density, but it scales only as (power density)(0.77). A last important issue in roll-to-roll processing of long runs is process stability and on-line quality control. The accurate measurement of self bias voltage and optical thickness of the deposited stacks have proven to be very useful in this context