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A study was conducted to investigate the influence of corona charges on the surface recombination velocity at the Si-SiO2 interface on both solar cells and lifetime test structures. A dramatic influence was observed in both cases. A new theoretical model was developed to include the effects of potential fluctuations to be able to quantitatively describe both the injection and surface potential dependence of the effective surface recombination velocity at corona charge surfaces.

Electroreflectance (ER), piezoreflectance (PZR) and secondary ion mass spectrometry (SIMS) were employed to analyze two In1-xGaxAsyP1-y/InP p-i-n multiple quantum well (MQW) solar cell structures with intrinsic (1)-InP spacers and two InP p-i-n samples. The composition, strain and well width of the MQWs were described by comparing the rich ER/PZR spectra from the MQW regions with an envelope function computation. From the electric fields coming from the i-InP region of the two InP p-i-n control samples, the amount of p-dopant interdiffusion was assessed based on the SIMS data. The results are discussed.

A study is conducted on the physical effects that occur when the size of the surface textures of a solar cell or photodiode is in the micron range. Results show that the most significant physical effects include light diffraction at the groove edges, interference of light reflected by various groove surfaces and tunneling across the grooved surface of light incident from the silicon side at an angle greater than the critical angle.

A model is derived to extract material parameters from an experimental electron-beam-induced current contrast profile across a vertical grain boundary. The model removes the need to reduce the experimental profile to a few integral parameters to obtain the least-squares values of the grain boundary recombination velocity and diffusion length in each grain. Diffusion length changes when collection efficiency is high will also have no effect on the model.

Shockley's standard model and Shockley and Quisser's detailed balance model for the diode are differentiated. The first one, which describes the monotical increase of the diode reverse saturation current with the device thickness. The detailed balance model, on the other hand, forecasts this current's saturation with increasing thickness. Furthermore, the standard model underestimates the computation of the limiting efficiency of solar cells. However, the differences diminish when the nonradiative recombination becomes significant.

A previously determined relationship between the probability of collection of a photogenerated carrier in a solar cell and the dark minority-carrier concentration at the point of generation is generalized to three-dimensional geometries with arbitrary doping profile and variable band gap including sudden compositional modifications, grain boundaries and floating junctions. The proof of the resulting relationship is simpler and more transparent than the previous work with more restricted geometries.

Analysis of electronic transport in a pn silicon solar cell via photothermal deflection shows that the method provides contactless optoelectronic characterization of photovoltaic cells. A semimicroscopic approach effectively simulates the dependence of deflection signals on external bias voltage in the closed circuit and base illumination in the open-circuit case.

A photoablation process using an UV excimer laser helps pattern Schottky barrier solar cells on Si surfaces. The patterned solar cells have an improved light collection efficiency, which is 23% more than nonpatterned cells. Schottky barriers with shallow and smooth surfaces have a barrier increase than those on flat surfaces.

Spin-dependent recombination and deep-level transient spectroscopic studies of electron-irradiated Czochralski silicon solar cells reveal recombination centers near the midgap level. An Si dangling-bond due to a vacancy cluster causes the formation of the centers. The hole and electron cross sections vary with temperature and represent minority-carrier lifetime of silicon.

The article examines the preparation, as well as the properties of the poly-(3-hexylthiophene) (P3HT) single walled carbon nanotube (SWNT) solar cells. These devices are shown to be much more effective and accurate, as compared to the only P3HT devices.

Several studies are conducted to determine the theoretical efficiencies exhibited by the hot carrier solar cells consisting of a bulk indium nitride absorber. The cell operations are shown to be highly influenced by the various impact ionization and Auger recombinations mechanisms.

The article discusses the synthesis and applications of the newly devised silicon nanowire (Si NW)-array-textured solar cells that can be used for different photovoltaic purposes. An increase in the surface recombination of the system while using these arrays is shown to lead to a significant reduction in the short circuit current.

Several theoretical simulations are conducted to explain the impact of different parameters like the indium content and thickness on the performance of the InGaN p-i-n single homojunction solar cells. The performance of these cells is shown to be highly dependent on the defect density of the i-layer, in addition to the various observed factors.

The relaxation of the assumption that series resistance is near zero while shunt resistance approaches infinity has affected the device performance differently depending on the chosen bulk heterojunction (BHJ) material system. The equivalent circuit model has used a light intensity dependent shunt resistance to describe the dissociation process and has predicted a photocurrent under reverse bias that has exceeded the photocurrent permitted by light absorption.

A transient response method is described that is used for measuring the minority carrier lifetime in inorganic semiconductors to measure the lifetime of free polarons in a polymer:fullerene bulk heterojunction (BHJ) solar cell. The lifetime of free polarons in poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acid methyl ester blend film is shown to be in the range of 300-400 ns.

Photoconductive atomic force microscopy is used for making local measurements of the open-circuit voltage ([V.sub.OC]) as a function of light intensity in many polymer/fullerene bulk heterojunction blend solar cells. The results have provided a method for mapping lateral variations in vertical structure/composition by making local measurements of [V.sub.OC] as a function of light intensity but have shown that the unusual light-intensity dependence of [V.sub.OC] of many organic photovoltaics is linked with morphological heterogeneity.

The effects of rapid thermal annealing (RTA) on the electrical, optical, structural, interfacial and surface properties of Nb:Ti[O.sub.2] (NTO)-Ag-NTO multilayer electrodes inserting a nanoscale Ag layer for application in organic solar cells (OSCs) are examined. The studies have shown that the activation of Nb dopants in the top NTO layer has played a major role in the extraction of carriers from the organic layer to the anode (NTO-Ag-NTO) electrode.

Incorporating UV-sensitive electron transport layers (ETLs) into organic bulk heterojunction (BHJ) photovoltaic devices has affected short-circuit current ([J.sub.SC]) and fill factor characteristics. Electro-optical modeling and light intensity experiments have shown that bimolecular recombination, in the form of diode current losses, has controlled the extracted photocurrent and is dependently on the ETL resistivity.

A new approach is described for small molecule organic solar cells by using highly doped organic layers, where the approach has adapts the use of tunnel diodes known from inorganic tandem solar cells. The results have shown that the concept has not depended on the specific choice of materials as it is seen for metal cluster based recombination contacts.

Several studies are conducted to explain the presence of the enhanced collection efficiency in the thin film silicon solar cells. The collection efficiency is shown to be completely dependent on the intensity of the bias and the monochromatic light.

Several modular studies are conducted to analyze the calibration of the different luminescence based voltage images of the silicon solar cells. A comparison of the different models is also presented.

The article presents a new analytical model, which can be employed for an effective recombination on the back surface of the locally contacted solar cell. The ways in which the three-dimensional problems can be reduced to one-dimensional problems are also analyzed.

Si[O.sub.2] multilayers with embedded Si nanocrystals (Si-ncs) are examined as an approach for developing highly efficient all Si tandem solar cells. Photocurrent I-V curves are measured in order to understand the optoelectronical behavior and recombination lifetimes are estimated by applying the transverse pump/probe technique.

Numerical simulations are used on GaAs solar cells with quantum wells (QWs) included in the intrinsic region between the emitter and base layer. The QWs have extended the absorption edge beyond that of the GaAs bandgap and the modeling of the solar cell characteristics is carried out within semiconductor simulation environment.

The performance of a series of heterojunction with intrinsic thin layer (HIT) solar cells on N-type crystalline silicon substrates with hydrogenated amorphous silicon (a-Si:H) emitter layers is simulated in order to understand the carrier transport and the general functioning of these devices. The studies have shown that the simulations have reproduced the electrical characteristics and temperature dependence for a set of devices with varying I-layer thickness.

Raman spectroscopy is used for determining the mechanical stress variation and the free hole concentration in laser crystallized amorphous silicon layers. The effect of film inhomogeneity in terms of stress and doping on the performance of a solar cell is discussed.

An electrical equivalent circuit is employed to explain the different dark current-voltage characteristics of the poly (3-hexylthiophene) (P3HT)/n-type crystalline silicon solar cells. The different parameters that affect the current at different temperatures are also discussed.

Several studies are conducted for the current matching of the subcells present in the small molecule organic tandem solar cells. The significance of the process in enhancing the performance of these cells is also demonstrated.

Several electroluminescence and photoluminescence measurements are conducted to analyze the reduced radiative recombination taking place in the low-well-number strain-balanced quantum well solar cells. The mechanisms leading to the reduction of the quasi-Fermi level separation (QFLS) in the devices are also discussed.

Several experiments are conducted for calculating the electronic, as well as the hole spectra of the three-dimensional superlattices that are shown to be formed from the layers of cylindrical rod arrays. These systems are shown to be highly efficient and hence can be easily used for numerous solar cell applications.

The surface passivation quality of nanocomposite amorphous silicon suboxides (a-Si[O.sub.x]:H) within both n-type and p-type silicon were studied as a function of injection level. The effective lifetime values achieved on a highly doped crystalline for n-type and p-type float zone (FZ) wafer feature a high quality passivation to yield effective lifetime values exceeding those of record Si[O.sub.2] and Si[N.sub.x] passivation schemes.

A method is described for determining spatially resolved minority carrier diffusion lengths in silicon solar cells from electroluminescence intensity ratios. A new method is introduced for determining spatially resolved integral excess charge density from single photoluminescence (PL) images, thereby rendering a calibration with another measuring technique unnecessary.

The transport mechanisms controlling the forward dark current-voltage characteristic of the silicon micromorph tandem solar cell are examined with numerical modeling methods. The dark current at high forward voltages is affected by the amount of electron-hole pairs thermally generated inside the recombination junction.

Si-rich-Si[O.sub.2] (SRSO)/Si[O.sub.2] multilayers (MLs) are grown by reactive magnetron sputtering and the presence of silicon nanoclusters (Si-ncls) within the SRSO sublayer and annealing temperature affect optical absorption as well as photoluminescence. The studies have shown that amorphous Si-ncl absorption is fourfold higher than that of crystalline Si-ncls.

The ZnS inserted solar cells are examined by photocurrent-voltage (I-V) and ac impedance spectroscopy (IS) measurements. The cell performance is controlled by the charge transport velocity at the ZnS/PCBM:P3HT interface.

A balance model is developed for the intermediate band (IB) solar cell, where the model has allowed the electron concentration in the IB to vary and has assumed a linear relation between the concentration and the absorption coefficients related to transitions over the subband gaps. The filling of the IB has varied with light intensity, cell voltage, density of IB-states and the positioning of the IB in the main band gap both for cells that are partially filled by doping and for photofilled cells.

The concept of a nanowire solar cell with photon-harvesting shells is described and the organic molecules that absorb strongly in the near infrared where silicon absorbs weakly are coupled to silicon nanowires (SiNWs). The organic molecules have absorbed the low-energy photons and have subsequently transferred the energy to the SiNWs via Forster resonant energy transfer, creating free electrons and holes within the SiNWs.

A simplified modal analysis is used for studying the behavior of the diffuse transmittance of lamellar diffraction gratings fpr solar cells. This modal analysis has predicted the optimum period and height for maximum light trapping for thin film solar cells with a front surface grating and flat rear reflector.

The high efficiency a-Si:H n-i-p solar cells fabricated with rf PECVD which utilize a p-type doped Si:H layer deposited at low temperature by using high hydrogen-to-silane flow ratio to achieve high circuit voltages [V.sub.OC's] is reported. The appearance of a low volume fraction of nanocrystals near the top transparent interface is found to be incidental to the high circuit voltages.

Extensive calculations are performed to study the influence of depth-to-period ratio of triangular and rectangular gratings on front reflectance. It is observed that gratings with triangular profile can feature very low reflectance when the depth-to-period ratio is very large and if periods are very small compared to light wavelength, light does not become tilted.

A study shows that the significance and importance of the combination of the back-contact barrier and a low absorber carrier density frequently lead to the alteration in the current-voltage (J-V) characteristics of CdTe solar cells. It is demonstrated that the back contact would lead to the generation of a wide depletion region and impedance of light-generated holes, which increases the injection of the electrons at the front diode, hence making the back space-charge region extremely important.

Spatial variations of the local open circuit voltage in Cu(In, Ge)[Se.sub.2] solar cells are examined using an electron beam induced voltage (EBIV) technique. Quantitative evaluation of EBIV signals has revealed that the loss of open circuit voltage due to the inhomogeneities is approximately 100 mV.

A study determined emitter saturation current densities of phosphorus-diffused planar c-Si solar cell emitters passivated by silicon carbide (Si[C.sub.x]) layers in a wide sheet resistance range (20-500 [OMEGA]/sq). The surface recombination velocity and the optical losses are determined for each configuration and used to calculate photovoltaic conversion efficiency limits for 50 and 90 [OMEGA]/sq emitters.

A different approach, based on electroluminescence, to detect mechanical defects in triple junction cells is presented. The approach, which can be extended to all planar semiconductor devices with at least one direct p-n junction, enables accurate, large area inspections while requiring only a simple measurement setup.

The device performance of solar cells based on multicrystalline SiGe(mc-SiGe) bulk crystal with microscopic compositional distribution grown by the casting method is presented. The results demonstrate that mc-SiGe is a promising candidate to replace mc-Si as it could achieve higher conversion efficiency without drastic increase of the production cost.

Spatially resolved images of the power losses in solar cells measured under realistic operational conditions are presented. A measurement technique called illuminated lock-in thermography is used and the underlying physics' of this technique are discussed.

The effects of nanostructured solar cells at a microscopic scale from those at a macroscopic scale are decoupled. The results for solid-state nanostructured cells indicate that the interconnection geometry is disadvantageous for the open circuit voltage and it is tolerant to moderate resistance in the n-TiO2 network, but not to resistance in the p-conductor.