Solar illumination conditions

Philae landing site selection process, the flight dynamics requirements of the Rosetta spacecraft and the comet s thermal and solar illumination conditions also had to be taken into account. The location chosen as the primary landing site for Philae was on the top of the smaller lobe of the comet. 

Fig. 5.2 The n-Cd(Se,Te)/aqueous Cs2Sx/SnS solar cell. P, S, and L indicate the direction of electron flow through the photoelectrode, tin electrode, and external load, respectively (a) in an illuminated cell and (b) in the dark. For electrolytes, m represents molal. Electron transfer is driven both through an external load and also into electrochemical storage by reduction of SnS to metaUic tin. In the dark, the potential drop below that of tin sulfide reduction induces spontaneous oxidation of tin and electron flow through the external load. Independent of illumination conditions, electrons are driven through the load in the same direction, ensuring continuous power output. (Reproduced with permission from Macmillan Publishers Ltd [Nature] [60], Copyright 2009)...

The more rectangular the. //E-curve appears, the higher the FF is and the better charge carriers are collected within the device. Finally, the conversion efficiency is defined as the ratio between electrical power density delivered by the solar cell under standard illumination conditions and the power density of the incident light Pnght... 

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]. 

The use of a reference cell is one simple method that gives reliable real-world performance estimates based on efficiencies measured in the laboratory where illumination conditions do not match the solar spectrum. This is the accepted... 

Several processable low bandgap PTs containing isothianaphthene units, such as 226, 227, and 228, have been reported for their use in bulk heterojunction PV devices with PCBM, with efficiencies 0.008%, 0.24%, and 0.31%, respectively, under simulated solar illumination [420—422]. A solar cell made from a mixture of 229/PCBM (1 1) led to an efficiency of 0.09% [423]. Polymer 230 presents a larger optical bandgap (2 eV) than that of 229 (1.3 eV) and a 1 1 mixture of 230 with PCBM leads to a PV cell of 0.024% of PCE under the same illumination conditions than for 229. 

Overall, the key condition for PEC hydrogen production is that the quasi-Fermi levels under solar illumination generate sufficient useable photopotential to drive the redox reactions for water splitting after all the solid-state, interfacial and solution overpotential losses have been taken into accoxmt. This challenge has severely limited efficiency in all single-junction PEC devices to date. 

Energy efficiencies in the order of 2% under solar illumination at AMO 1 sun conditions were obtained on the systems described above [6], which is much lower than expected, and we continue to channel efforts in this direction with the aim of reaching efficiency values of the order of 10%. 

The single most important performance parameter of a solar cell is the power conversion efficiency (PCE or rj), which is related with the open circuit voltage (V )/ short circuit current (J ) and fill factor (Ff) through equation (1). All of those parameters can be extracted from the J-V curves under the 1 sun condition (100 mW/cm simulated AMI.5 solar illumination) (Scheme 3.8). The PCE is calculated by the following equation ... 

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