Solar conversion efficiency

Pig. 1. An integrated high concentration photovoltaic array that achieved a solar conversion efficiency exceeding 20% in a 2000-W testbed (7). 

Kressin AM, Doan VV, Klein JD, Sailor MJ (1991) Synthesis of stoichiometric cadmium selenide films via sequential monolayer electrodeposition. Chem Mater 3 1015-1020 Miller B, Heller A, Robbins M, Menezes S, Chang KC, Thomson JJ (1977) Solar conversion efficiency of pressure sintered cadmium selenide liquid junction cells. J. Electrochem Soc 124 1019-1021. 

It has been illustrated that polycrystalline materials can be operated in regenerative electrolytic solar cells yielding substantial fractions of the respectable energy conversion efficiency obtained by using single crystals. Pressure-sintered electrodes of CdSe subsequently doped with Cd vapor have presented solar conversion efficiencies approaching 3/4 of those exhibited by single-crystal CdSe electrodes in alkaline polysulfide PEC [84]. 

Menezes S (1984) 12% solar conversion efficiency by interface restructuring. Appl Phys Lett 45 148-149... 

Fig. 5.65 Dependence of the solar conversion efficiency (CE) on the threshold wavelength (Ag) for a quantum converter at AM 1.2. Curve 1 Fraction of the total solar power convertible by an ideal equilibrium converter with no thermodynamic and kinetic losses. Curve 2 As 1 but the inherent thermodynamic losses (detailed balance and entropy production) are considered. Continuous line Efficiency of a regenerative photovoltaic cell, where the thermodynamic and kinetic losses are considered. The values of Ag for some semiconductors are also shown (according to J. R. Bolton et al.)... 

The theoretical solar conversion efficiency of a regenerative photovoltaic cell with a semiconductor photoelectrode therefore depends on the model used to describe the thermodynamic and kinetic energy losses. The CE values, which consider all the mentioned losses can generally only be estimated the full line in Fig. 5.65 represents such an approximation. Unfortunately, the materials possessing nearly the optimum absorption properties (Si, InP, and GaAs) are handicapped by their photocorrosion sensitivity and high price. 

These experiments indicated that an increase of solar conversion efficiency on the order of 50% can be achieved for cells containing Ti02 mesoporous films with a thickness >1 pm.5... 

Fig. 3.20 The ideal limiting solar conversion efficiency for single bandgap devices. The dotted line shows efficiency of photoelectrolysis cells at different values of Eioss in relation (3.6.8) [102].

Though equation (3.6.5) is more useful for analyzing the performance of photoelectrolysis cells, for practical purposes the photoconversion efficiency (solar conversion efficiency if sunlight is used) is calculated hy modifying (3.6.5) in the form... 

Hanna MC, Nozik AJ (2006) Solar conversion efficiency of photovoltaic and photoelectrolysis cells with carrier multiplication absorbers. J Appl Phys 100 074510 (8 pages)... 

Simulated solar conversion efficiencies up to 6.8% on Ti substrates have been reported for annealed CD CdSe films in polysulphide electrolyte based on a low-ammonia-concentration-selenosulphate bath. Several successive depositions were required to build up an optimum final fihn thickness of 2.5 jim (when most of the hght was absorbed). The initial deposit was annealed to improve adherence and the final multideposited film was annealed at 550°C in air, followed by etching and zinc ion treatment. 

Solar conversion efficiencies for amorphons cells are increasing steadily, bnt again the performance of devices critically depends on the mobility and lifetime of excess photocarriers in the films. 

In order to get an estimate of the solar-to-electrical conversion efficiency on layered compounds, sample D has been measured in sunlight. The result, obtained at 92.5mW/cm2 insolation is shown in Fig. 8. The maximum power point is at 0.33V and 10.7mA/cm2, with a resulting solar conversion efficiency of 3.7%. As is evident from Fig. 7, some samples show better overall performance than sample D. The best of these, sample G, the surface of which was accidentally damaged before being measured in the sun, had a maximum power output which exceeded that of sample D by a factor of 1.4 bringing the estimated solar conversion efficiency to 5.2%. 

Figure I. Results of an 8-month outdoors test of PEC containing a 0.8-cm2 thin film, painted CdSe photoelectrode (not photoetched), CoS counterelectrode, and 7M KOH, 2M S, 7M S, ImM Se solution. (OCV) open-circuit voltage (SCC) short-circuit current (EFF) solar conversion efficiency ( AMI.5). Between measurements the cell operated on maximum power (68 fi load). No appreciable change in fill-factor occurred during the test.

Solar conversion efficiency The ratio of the Gibbs energy gain per unit time per nf of surface exposed to the sun to the solar irradiance, E, integrated between X = 0 and X = 00. 

In competition with photocurrent production, the Fe " can oxidize S or L. Experimental data strongly suggests that recombination with S is the main factor that lowers overall efficiency [20]. Attempts to increase the efficiency by replacing thionine with Ru(bpy)3 were not successful from a practical point of view [38]. Other issues regarding the optimum diffusion length, solute concentration and selectivity of the electrodes have been considered. Theoretical solar conversion efficiencies of 0.13 are believed to be achievable by this general approach. The highest efficiency measured to date is only 3 x 10 [23]. 

Dye sensitization of electrodes is an old area of science with a rich history. The field has experienced renewed interest owing to the development of high surface area colloidal semiconductor electrodes. These materials yield impressive solar conversion efficiencies when employed in regenerative solar cells that have already found niche applications and have the real possibility of replacing traditional solid-state photovoltaics. Thus for the first time in history a solar cell designed to operate on a molecular level is useful from a practical point of view. It is also likely that other applications in the growing areas of molecular photonic materials will arise. 

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