Hybrid solar cells, efficient

The hybrid solar concentrator is a potential leap frog technology that may rapidly lower the cost of clean hydrogen in light of the following the imminent market entry of CPV systems for electricity production solar cell efficiencies above 40%, with clearer ideas for 50%-efficient solar cells and the opportunity to use wasted solar heat for augmenting solar electrolysis. 

Snaith H. J., Moule A. J., Klein C., Meerholz K., Friend R. H. and Gratzel M. (2007), Efficiency enhancements in solid-state hybrid solar cells via reduced charge recombination and increased light capture , Nano Letters 7, 3372-3376. 

Beek W. J. E., Wienk M. M. and Janssen R. A. J. (2004), Efficient hybrid solar cells from zinc oxide nanoparticles and a conjngated polymer , Adv. Mat. 16, 1009-1012. 

One extensively studied material system among the nanocrystal-polymer blends is zinc oxide (ZnO) in combination with MDMO-PPV or P3HT [273-282]. Beek et al. presented the first polymer solar cells containing ZnO nanoparticles, reaching power conversion efficiencies of 1.6% [273]. In this case the nanoparticles were prepared separately and then intermixed with MDMO-PPV in solution. Shortly after this study the Janssen group presented another route to ZnO-polymer hybrid solar cells by forming the nanocrystals in situ inside the film by applying a precursor [274]. Here, diethylzinc served as the precursor and was spin cast in blends with MDMO-PPV. Process-... 

Ackermann, J. et ah. Highly efficient hybrid solar cells based on an octithiophene-GaAs heterojunction, A(7v. Eunct. Mater. 15, 810-817, 2005. 

In bulk (or dispersed) heterojunctions, nanocrystals are blended into the polymer to create a heterogeneous composite with a high interface surface area. In this hybrid solar cell concept, photo induced charge separation is favored between high electron affinity inorganic semiconductors and relatively low ionization potential polymer. The maximum power conversion efficiency has reached 2.8 % under AM 1.5 illumination condition by using the composite of tetrapods of CdSe nanocrystals and MDMO-PPV [4], while the PCE of the device based on the composite of CdTe nanorods and MEH-PPV is only 0.052 % in similar conditions [5]. 

H. J. Snaith, A. J. Moule, C. Klein, K. Meerholz, R. H. Friend, M. Gratzel, Efficiency Enhancements in Solid-State Hybrid Solar Cells via Reduced Charge Recombination and Increased Light Capture. Nano Lett. 2007, 7, 3372-3376. 

The above chemical coupling leads to uniform dispersion (as inferred from TEM images) of QCNs within CP matrix [162] leading to improved charge transfer/transport and enhancement of optoelectronic performance, e.g., light-to-electricity conversion efficiency in hybrid solar cells. 

Ihe Ught-to-electricity conversion efficiency or QE of hybrid solar cell is governed by the five basic steps involved in the process (Shown schematically in Figure 3.22) viz. light absorption by active material to form excitons (1), exciton diffusion toward interface (2), exciton dissociation at interface (3), free carriers (electron/hole) transport toward electrodes (4), and charge collection at respective electrodes (5) [178-180]. 

Y. Zhou, F. S. Riehle, Y. Yuan, H.-F. Schleiermacher, M. Niggemann, G. A. Urban, M. Kruger, Improved Efficiency of Hybrid Solar Cells Based on Non-Ligand-Exchanged CdSe Quantum Dots and Poly(3-Hexylthiophene). Applied Physics Letters 2010,96,013304. 

Y. Zhou, M. Eck, C. Veit, B. Zimmermann, F. Rauscher, P. Niyamakom, S. Yilmaz, I. Dumsch, S. Allard, U. Scherf, Efficiency Enhancement for Bulk-Heterojunction Hybrid Solar Cells Based on Acid Treated CdSe Quantum Dots and Low Bandgap Polymer PCPDTBT. Solar Energy Materials and Solar Cells 2011,95,1232-1237. 

W. J. E. Beek, M. M. Wienk, R. A. J. Janssen, Efficient Hybrid Solar Cells from Zinc Oxide Nanoparticles and a Conjugated Polymer. Advanced Materials 2004,16,1009-1013. 

K. E Jeltsch, M. Schadel, J.-B. Bonekamp, P. Niyamakom, E Rauscher, H. W. A. Lademann, I. Dumsch, S. Allard, U. Scherf, K. Meerholz, Efficiency Enhanced Hybrid Solar Cells Using a Blend of Quantum Dots and Nanorods. Advanced Functional Materials 2012,22, 397-404. 

Y. Zhou, et al. Efficiency enhancement for bulk-heterojunction hybrid solar cells based on acid treated CdSe quantum dots and low bandgap polymer PCPDTBT. Solar Energy Materials Solar Cells, 2011.95(4) p. 1232-1237. 

R. Zhu, et al. Highly efficient nanoporous TiOj-polythiophene hybrid solar cells based on interfacial modification using a metal-free organic dye. Advanced Materials, 2009. 21(9) p. 994-1000. 

R. Thitima, et al. Efficient electron transfers in ZnO nanorod arrays with N719 dye for hybrid solar cells. Solid-State Electronics, 2009. 53(2) p. 176-180. 

Table 13.3 Sum maty of high efficient hybrid solar cell results with details about the material composition, treatment and hybrid film formation as well as best c parameters obtained. 

Snaith et al. utilized the so-called polymer brushes as hole conductors in hybrid solar cell devices. CdSe NCs have been attached to the brushes by infiltration to form a thin hybrid film [104]. Devices showed an improved hole conduction compared to spin-coated films of the same polymer [105]. However, device efficiencies remained quite low due to limited absorption of the solar light. 

---