Proceedings of the European Summer School of Photovoltaics 4 â 7 ...

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I[µA/cm 2 ] 15 10 5 0 -5 -10 I[µA/cm 2 ] 15 10 5 0 -5 -10 Fig. 4. Typical architecture of the photovoltaic device electrons) while ITO is applied as the anode for the purposes of collecting holes. Active layer thickness is about 150 nm. The overall architecture of the device is presented in Fig. 4. Results Current-voltage (I-V) characteristics of the device were measured using the Keithley 2400 source-meter. Device was illuminated with maximum intensity of 1.3 mW/cm 2 . I-V characteristics after illumination are given in the Fig. 5, 6, 7 and 8. -15 -20 -0,5 0,0 0,5 1,0 1,5 V[V] a) b) Fig. 7. I–V characteristic of: a) ITO/PAQX3+P3OT/Al, b) ITO/PEDOT: PSS/PAQX3+P3OT/Al 30 20 -15 -20 -1,0 -0,5 0,0 0,5 1,0 1,5 2,0 15 10 5 V[V] 10 5 15 10 I[µA/cm 2 ] 10 0 -10 I [µΑ/cm 2 ] 0 -5 -10 I[µA/cm 2 ] 0 -5 -10 -15 -20 -0,5 0,0 0,5 1,0 1,5 V[V] a) b) -25 -0,5 0,0 0,5 1,0 1,5 V[V] Fig. 5. I–V characteristic of: a) ITO/PAQX1+P3OT/Al, b) ITO/PEDOT: PSS/PAQX1+P3OT/Al I[ µ A/cm2] 5 0 -5 -10 -15 -20 -20 -30 -0,5 0,0 0,5 1,0 1,5 V[V] a) b) Fig. 8. I–V characteristic of: a) ITO/PAQX4+P3OT/Al, b) ITO/PEDOT: PSS/PAQX4+P3OT/Al Solar cells parameters extracted from I–V characteristics in the Fig. 5, 6, 7 and 8. -15 -20 -1,0 -0,5 0,0 0,5 1,0 1,5 2,0 U[V] I[µA/cm 2 ] 15 10 5 0 -5 -10 -15 IµA/cm 2 ] 15 10 5 0 -5 -10 -15 Cell V oc [V] I SC [μA/cm 2 ] FF η (%) ITO/PAQX1+P3OT/Al 0,8 12,24 0,27 0,2 ITO/PEDOT:PSS/PAQX1+P3OT/Al 1,13 18,2 0,17 0,27 ITO/PAQX2+P3OT/Al 0,58 8,45 0,23 0,086 ITO/PEDOT:PSS/PAQX2+P3OT/Al 0,9 10,36 0,24 0,17 ITO/Z1+P3OT/Al 0,59 5,39 0,22 0,053 -20 -0,5 0,0 0,5 1,0 1,5 V[V] a) b) -20 -0,5 0,0 0,5 1,0 1,5 2,0 Fig. 6. I–V characteristic of: a) ITO/PAQX2+P3OT/Al, b) ITO/PEDOT: PSS/PAQX2+P3OT/Al V[V] ITO/PEDOT:PSS/Z1+P3OT/Al 1,22 5,12 0,16 0,076 ITO/PAQX4+P3OT/Al 0,86 4,29 0,19 0,053 ITO/PEDOT:PSS/PAQX4+P3OT/Al 0,56 10,06 0,25 0,11 Summary Conjugated PEDOT:PSS polymers have much lower mobility than inorganic semiconductors and are traditionally better for conducting holes than electrons. Typical hole mobilities range are about 0.001 cm 2 V -1 s -1 [1]. Additional layer of PEDOT:PSS facilitates transport of charge carriers to electrode. As one can see in cells with PEDOT:PSS layer energy conversion efficiency increased in comparison to the cell with the same active layer. We obtained the best energy conversion efficiency for the architecture ITO/PEDOT:PSS/PAQX1+P3OT/Al. Results of this work proved that photovoltaic cells need further modification in order to increase energy conversion efficiency. References [1] Gondek E., A. Danel, I. V. Kityk, J Mater Sci: Mater Elctron (2009) 20:461-468. [2] Sanetra J.: Efekt fotowoltaiczny w organicznych ogniwach słonecznych – wybrane zagadnienia. PK, Krakow, 2006. [3] Gondek E., I. V. Kityk, A. Danel, J. Sanetra: SpectrochImica Acta Part A 70 (2008) 117–121. 130 Elektronika 6/2012
The influence of inclination and azimuth angle of PV modules on the energetic gain Artur Bugała, Grażyna Frydrychowicz-Jastrzębska Poznań University of Technology The angle of incidence of solar radiation on the PV panel or plane is a function on many factors: the angle of solar declination, the angle of latitude, the hour angle, the azimuth angle and the angle of receiver inclination to the ground. The declination angle depends on the day of the year, the hour angle taking the value in accordance to the time of the day, the angle of the latitude depends on the location. The next parameter, that is the azimuth angle of the receiver is the deflection accounted from the local meridian to the south direction [4]. Dependence of the energy possible from Sun on the above mentioned parameters may be reduced by optimal orientation of the PV panel. Many authors dealt with this problem [1, 2, 3, 4, 6, 7]. Density of solar radiation flux Total solar radiation is a hemispherical radiation, achieving the receiver surface of any spatial orientation, from the solid angle in the range 2π [sr], supplemented by the component reflected from the ground and from the objects surrounding the receiver. In particular case of a receiver located in parallel to the ground the reflected component does not exist. Direction of incidence of the direct radiation at an inclined surface is evident – it is identical to the direction of the radiation beam. In case of the receiver that is inclined with respect to the ground proper definition of the diffused radiation is the most difficult. Three components should be specified in this radiation: – isotropic radiation; – circumsolar radiation; – the radiation coming from the bright horizon. The first of these components is distinguished by the fact that it comes uniformly from the whole hemisphere. On the other hand, the circumsolar component is a result of diffusion of the solar radiation. Nevertheless, it is specifically related to the direct component. The third component is focused near to the horizon and observable in case of clear sky. Additionally, in case of the receiver inclined at a certain angle β≠0 to the ground the radiation reflected from the ground and surrounding objects should be considered to, apart from the direct and diffused components of radiation, all being the components of the so-called total radiation. The Authors of early computational models focused chiefly at determining the direct component, devoting considerably less attention to the other ones. The diffused radiation was considered as an isotropic one. Such an approach is appropriate, but only in case of the surfaces located in parallel to the surface of Earth. One of the first methods, that partially took into account the effect of receiver inclination is the Liu-Jordan method [8]. The authors introduce correction factors into the calculation. Nevertheless, the method does not fully reflect the complex character of the diffused component, as in the proposed model it is considered as an isotropic one. Since the time of development of the Liu-Jordan method, i.e. about 50 years ago, many mathematical models have been developed, that allowed to determine the total density of the solar radiation incident on the arbitrarily oriented receiver surface. However, they are more complex from the mathematical point of view. The HDKR model seems to be particularly appropriate. It is a result of the methods developed by several authors, i.e. the models of J.E. Hay, J.A. Davies, T.M. Kluchera, and D.T. Reindl [5]. In the first of them the authors assume isotropic distribution of the diffused radiation, considering the diffused, isotropic, and circumsolar components. The effect of anisotropy was here taken into account only as a function of atmospheric transparency for the direct radiation. D.T. Reindl supplemented the mathematical apparatus by the component resulting from the bright horizon. T.M Klucher inserted the effect of clouding factor to the correction factor of the bright horizon of the equation derived by Reindl. The relationship modified by him explains the considered components with sufficient accuracy, even in case of the receivers inclined at large angles with respect to the ground [5]. The Liu – Jordan Method Authors of the present paper used the Liu-Jordan method. Its advantage lies in rather simple mathematical apparatus [8]. Moreover, comparison of the results obtained by other authors [3] for the calculation carried out both with the method considering anisotropy of the diffusion radiation and ignoring its effect, has shown that the results of the radiation power density in yearly scale differ only slightly. In case of the Liu-Jordan method the results are a little lower as compared to the ones obtained with consideration of anisotropy. Specification of the example results obtained with the isotropic and anisotropic methods is presented in Table [3]. According to the example data of Table, maximum of the function of solar radiation power density in yearly scale incident at the plane inclined and directed at appropriate azimuth angle occurs for the angles β = 30°, γ = 15° for the isotropic model, or for β = 40° and γ = 15° in case of consideration of anisotropy. Differences in the calculation results obtained with both methods usually are of the order of several percent, reaching even 1 percent in case of small inclination of the receiver with respect to the ground. Maximum difference occurs in case of vertical orientation, i.e. for photovoltaic applications existing in case of façade BIPV solutions. Under our geographical and weather conditions the Liu-Jordan method is well justified. In summer months, when higher factor of anisotropy may be expected, the optimal inclination angle is not large, due to power gain, reaching the values of 25–35°. On the other hand, in winter conditions the optimal inclination angle amounts to 55–60°. Therefore, the isotropic Liu-Jordan model may be used with sufficient accuracy, particularly in case of lower power systems [4, 8]. Tabl. Maximum power density in yearly scale falling at an inclined plane directed at appropriate azimuth angle Model The angles β and azimuth angle γ β = 20° γ = 15° β = 30° γ = 15° β = 40° γ = 15° β = 45° γ = 15° β = 60° γ = 20° β = 80° γ = 25° β = 90° γ = 30° Isotropic computation model 3870 MJ/m 2 3900 MJ/m 2 3870 MJ/m 2 3850 MJ/m 2 3600 MJ/m 2 3100 MJ/m 2 2740 MJ/m 2 Anisotropic computational model 4000 MJ/m 2 4100 MJ/m 2 4140 MJ/m 2 4120 MJ/m 2 3900 MJ/m 2 3450 MJ/m 2 3100 MJ/m 2 Elektronika 6/2012 131
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Proceedings of the European Summer
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