We report on the use and effect of the alkali elements rubidium and caesium in the place of sodium and potassium in the alkali post deposition treatment (PDT) as applied to Cu(In,Ga)Se2 (CIGS) solar cell absorbers. In order to study the effects of the different alkali elements, we have produced a large number of CIGS solar cells with high efficiencies resulting in a good experimental resolution to detect even small differences in performance. We examine the electrical device parameters of these fully functional devices and observe a positive trend in the I –V parameters when moving from devices without PDT to KF‐, RbF‐, and eventually to CsF‐PDT. A diode analysis reveals an improved diode quality for cells treat‐ed with heavier alkalis. Furthermore, secondary ion mass spectrometry (SIMS) measurements reveal a competitive mechanism induced within the class of alkali elements in the CIGS absorber induced by the alkali post deposition treatment. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

In this contribution, we present a new certified world record efficiency of 20.1 and 20.3% for Cu(In,Ga)Se2 thin‐film solar cells. We analyse the characteristics of solar cells on such a performance level and demonstrate a high degree of reproducibility. Copyright © 2011 John Wiley & Sons, Ltd.

P. Jackson et al.: Cu(In,Ga)Se 2 solar cells with new record efficiencies up to 21.7%

ContentsFull text on our homepage at www.pss-rapid.com FRONT COVERThin films of Cu(In,Ga)Se 2 (CIGS) due to their exceptionally good light absorption properties can get by with a very thin photoactive layer of only 2-3 µm whilst still catching the sun's energy. With such a sparing use of materials as compared to traditional technologies based on silicon, thin-film solar cells promise a major production cost reduction. Up to now, however, thin-film photovoltaics never could reach the same conversion efficiency level as the silicon based devices. Now CIGS, with a new record efficiency of 20.8% on the laboratory scale (see the Letter by Philip Jackson et al.,, for the first time outshines a major silicon competitor, multicrystalline silicon (20.4%). The key to this break-through was the application of a new doping technique. Doping in CIGS is significantly more complex than in silicon solar cells due to its multinary structure, the various intrinsic crystal defects and the diffusion of various contaminants from the glass substrate. The improvement in controlling this complex doping process has led to a remarkable increase in device performance. Due to the more complex physical and chemical environment of CIGS and the resulting multifaceted interactions, the new doping technique also enables production of CIGS solar cells with higher band gaps and higher open-circuit voltages. BACK COVERAs shown by , by generating a wavy architecture in classical transistor topology, high output current is achieved -opening up bold futuristic opportunity for ultra-high resolution bright display. Irrespective of the material choice -the unique architecture can provide exciting thin film transistor performance enhancement. Hanna et al. demonstrate the advantage of using the wavy architecture in terms of area efficiency, higher output current, higher field-effect mobility and similar OFF current levels and I on /I off ratios compared to the planar counterparts for a thin film transistor fabricated with zinc oxide channel material. The low OFF current levels and high I on /I off ratios for the wavy-channel devices ensure that standby power consumption remains similar to the planar counterparts, while improving the ON current values. This proves the significance of this new architecture for large-area high-resolution display applications. NEW IN pssPage 216-217 ___________ Recent and forthcoming publications in pss Radial distribution of iron in silicon crystals grown by Czochralski method from contaminated feedstockStrong suppression of iron precipitation is detected near to the rims of Cz-Si crystals grown from iron-contaminated feedstock. At the achieved accuracy level, iron shows a homogeneous radial distribution, however, it is mainly in the FeB state close to the crystal rims and in the form of silicide precipitates in the rest of the crystal. Lambertian light trapping in thin crystalline macroporous Si layersLambertian light trapping is a benchmark for efficient light trapping. In this Letter the authors experimentally quantify t...

Chalcopyrite solar cells achieve efficiencies above 23%. The latest improvements are due to post‐deposition treatments (PDT) with heavy alkalis. This study provides a comprehensive description of the effect of PDT on the chemical and electronic structure of surface and bulk of Cu(In,Ga)Se2. Chemical changes at the surface appear similar, independent of absorber or alkali. However, the effect on the surface electronic structure differs with absorber or type of treatment, although the improvement of the solar cell efficiency is the same. Thus, changes at the surface cannot be the only effect of the PDT treatment. The main effect of PDT with heavy alkalis concerns bulk recombination. The reduction in bulk recombination goes along with a reduced density of electronic tail states. Improvements in open‐circuit voltage appear together with reduced band bending at grain boundaries. Heavy alkalis accumulate at grain boundaries and are not detected in the grains. This behavior is understood by the energetics of the formation of single‐phase Cu‐alkali compounds. Thus, the efficiency improvement with heavy alkali PDT can be attributed to reduced band bending at grain boundaries, which reduces tail states and nonradiative recombination and is caused by accumulation of heavy alkalis at grain boundaries.