semitransparent polymer solar cells

be seen that reflectance peaks are redshifted gradually and would match better to the absorption spectra of the active layer (400–650 nm) when the thickness of the V2O5 capping layer increases Fig 4a shows the the J–V characteristics of semitransparent inverted polymer solar cells under AM1.5G illumination of 100 mW/cm2 when illuminated from ITO side (Bottom) The detailed results are given in Table When the thickness of V2O5 is 40 nm, the Jsc is 4.83 mA/cm2, the Voc is 0.581 V, the FF is 60.6%, and the PCE is 1.70% When Fig (a) The transmittance spectra of the transparent electrode V2O5 (10 nm)/Ag (13 nm)/V2O5 (x = 0, 20, 40, 60, 80 nm) (b) the reflectance spectra of the transparent electrode V2O5 (10 nm)/Ag (13 nm)/V2O5 (x = 0, 20, 40, 60, 80 nm) metal film (13 nm Ag here) is higher than that of the bulk metal due to the scattering of the electrons from the surface of the discontinuous film The outer V2O5 decreases the series resistance (Rsc), which is defined by the slope of the J–V curve at J = mA/cm2 The series resistance is estimated to be 33.6X for device I and 23.3X for device P The decrease of Rsc results in the increase of FF from 0.540 to 0.606 Fig 2b shows the J–V characteristics of semitransparent inverted polymer solar cells (device I and P) under AM1.5G illumination of 100 mW/cm2 when illuminated from V2O5/Ag/V2O5 side (Bottom) Here, the mixture of P3HT and PCBM, which has main absorption spectrum from 400 to 650 nm, is chosen as active layers The photocurrent density is in direct proportion to light absorption of the active layer Since device P has higher transmittance from 400 to 650 nm, as shown in Fig 3a, it has bigger Jsc than device I Fig 3a shows the transmittance spectra of the V2O5/Ag/ V2O5 from 300 to 1000 nm It can be seen that the transmittance becomes week with the increase of wavelength, and high transmittance of 80% appears in short wavelength range when the thickness of V2O5 is zero When introducing outer V2O5 (capping layer), the transmittance is Fig The J–V characteristics of device ITO/nc-TiO2/P3HT: PCBM/V2O5 (10 nm)/Ag (13 nm)/V2O5 (x = 20, 40, 60, 80 nm) dependent on the thickness of the V2O5 capping layer when illuminated from (a) ITO side and (b) from V2O5/Ag/V2O5 side 1226 L Shen et al / Organic Electronics 12 (2011) 1223–1226 the thickness of V2O5 is 80 nm, the photovoltaic device has a Jsc of 5.96 mA/cm2, Voc of 0.594 V, FF of 59.8%, and PCE of 2.12% The Jsc of the device with 40 nm V2O5 is the smallest; and the Jsc of the device with 80 nm V2O5 is the biggest It is known that the reflectance of the top electrode plays an important role in trapping light for the active layer to reabsorb The reflectance of V2O5/Ag/V2O5 (80 nm) from 400 to 650 nm is the strongest, but the reflectance of V2O5/Ag/ V2O5 (40 nm) is poorest in Fig 3b Fig 4b shows the the J–V characteristics of semitransparent inverted polymer solar cells under AM1.5G illumination of 100 mW/cm2 when illuminated from V2O5/Ag/ V2O5 side (Top) The detailed results are given in Table When the thickness of V2O5 is 40 nm, the Jsc is 3.79 mA/ cm2, the Voc is 0.565 V, the FF is 60.6%, and the PCE is 1.30% When the thickness of V2O5 is 80 nm, the photovoltaic device has a Jsc of 2.67 mA/cm2, Voc of 0.551 V, FF of 59.8%, and PCE of 0.88% The Jsc of the device with 40 nm V2O5 is the biggest, and that for the device with 80 nm V2O5 is the smallest This is because the transmittance of V2O5/Ag/V2O5 (40 nm) is the highest, and the absorption of active layer material is directly proportional to the transmittance of the incidence electrode When illuminated from V2O5/Ag/V2O5 side, the Voc becomes smaller compared with that illuminated from the ITO side The dependence of the Voc and the photocurrent (Iph) can be generally expressed as follows [21]: V oc ẳ   Iph kT Log ỵ1 q Is 1ị Where Is is reverse saturation current, k is Boltzman constant, T is the temperature, and q is charge Under Eq (1), the Voc is directly proportional to Iph The Iph from ITO side is much bigger than that from V2O5/Ag/V2O5 side, which is shown in Table 40 nm, the highest transmittance is obtained The reflectance peaks are redshifted gradually and would match better to the absorption spectra of the P3HT: PCBM layer when the thickness of the V2O5 capping layer increases Acknowledgements The authors are grateful to Major Project of Science and Technology Development Plan of Jilin Provincial Science and Technology Department (Grant Nos 20070402, 20080330, 20100103), the China 863 Program (Grant No 2007AA03Z406, 2009AA032402), Scientific Frontier and Interdiscipline Innovative Projects of Jilin University (Grant Nos 200903087), National Natural Science Foundation of China (Grant Nos 60977031, 50977038, 61007022, 61077046, 61006013) and Doctoral Found of Ministry of Education of China Grant Nos 20090061110040, 20100061120045 for the support to the work References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] Conclusion [16] In summary, we present efficient semi-transparent inverted polymer solar cells with highly transparent V2O5/ Ag/V2O5 anodes The inner V2O5 layer was introduced as a buffer layer to improve holes collection, while the outer V2O5 served as a light coupling layer to enhance optical transmittance The incident light transmittance changed with the thickness of V2O5.When the thickness of V2O5 is [17] [18] [19] [20] [21] M Helgesen, R Søndergaard, F.C Krebs, J Mater Chem 20 (2010) 36 F.C Krebs, Sol Energy Mater Sol Cells 93 (2009) 394 C Deibel, V Dyakonov, Rep Prog Phys 73 (2010) 096401 R Po, M Maggini, N Camaioni, J Phys Chem C 114 (2010) 695 F.C Krebs, T.D Nielsen, J Fyenbo, M Wadstrøm, M.S Pedersen, Energy Environ Sci (2010) 512 F.C Krebs, J Fyenbo, M Jørgensen, J Mater Chem 20 (2010) 8994 F.C Krebs, T Tromholt, M Jørgensen, Nanoscale (2010) 873 S.H Park, A Roy, S Beaupré, S Cho, N Coates, J.S Moon, D Moses, M Leclerc, K Lee, A.J Heeger, Nat Photonics (2009) 297 H.Y Chen, J Hou, S Zhang, Y Liang, G Yang, Y Yang, L Yu, Y Wu, G Li, Nat Photonics (2009) 649 P Peumans, A Yakimov, S.R Forrest, J Appl Phys 93 (2003) 3693 G Dennler, M C Scharber, C J Brabec, Adv Mater 21 (2009) 1323 T Ameri, G Dennler, C Lungenschmied, C J Brabec, Energy Environ Sci (2009) 347 J Gilot, M.M Wienk, R.A.J Janssen, Appl Phys Lett 90 (2007) 143512 F.C Chen, J.L Wu, K.H Hsieh, W.C Chen, S.W Lee, Org Electron (2008) 1132 G.M Ng, E.L Kietzke, T Kietzke, L.W Tan, P.K Liew, F.R Zhu, Appl Phys Lett 90 (2007) 103505 V Shrotriya, G Li, Y Yao, C Chu, Y Yang, Appl Phys Lett 88 (2006) 073508 K Norrman, M.V Madsen, S.A Gevorgyan, F.C Krebs, J Am Chem Soc 132 (2010) 16883 C Tao, S.P Ruan, X.D Zhang, G.H Xie, L Shen, X.Z Kong, W Dong, C.X Liu, W.Y Chen, Appl Phys Lett 93 (2008) 193307 L Shen, G.H Zhu, W.B Guo, C Tao, X.D Zhang, C.X Liu, W.Y Chen, S.P Ruan, Z.C Zhong, Appl Phys Lett 92 (2008) 073307 V Shrotriya, G Li, Y Yao, T Moriarty, K Emery, Y Yang, Adv Funct Mater 16 (2006) 2016 A Moliton, J.M Nunzi, Polym Int 55 (2006) 583  ... V2O5 (40 nm) is poorest in Fig 3b Fig 4b shows the the J–V characteristics of semitransparent inverted polymer solar cells under AM1.5G illumination of 100 mW/cm2 when illuminated from V2O5/Ag/... [13] [14] [15] Conclusion [16] In summary, we present efficient semi-transparent inverted polymer solar cells with highly transparent V2O5/ Ag/V2O5 anodes The inner V2O5 layer was introduced as... M Helgesen, R Søndergaard, F.C Krebs, J Mater Chem 20 (2010) 36 F.C Krebs, Sol Energy Mater Sol Cells 93 (2009) 394 C Deibel, V Dyakonov, Rep Prog Phys 73 (2010) 096401 R Po, M Maggini, N Camaioni,