This dissertation describes the study of organic thin-film solar cells in pursuit of affordable, renewable, and environmentally-friendly energy sources. Particular emphasis is given to the molecular ordering found in liquid crystalline or polycrystalline films as a way to leverage the efficiencies of these types of cells. Maximum efficiencies estimated based on excitonic character of organic solar cells show power conversion efficiencies larger than 10% are possible in principle. However, their performance is often limited due to small exciton diffusion lengths and poor transport properties which may be attributed to the amorphous nature of most organic semiconductors.Discotic liquid crystal (DLC) copper phthalocyanine was investigated as an easily processible building block for solar cells in which ordered molecular arrangements are enabled by a self-organization in its mesophases. An increase in photocurrent and a reduction in series resistance have been observed in a cell which underwent an annealing process. X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements suggest that structural and morphological changes induced after the annealing process are related to these improvements.In an alternative approach, p-type pentacene thin films prepared by physical vapor deposition were incorporated into heterojunction solar cells with C60 as n-type layers. Power conversion efficiencies of 2.7 % under broadband illumination (350-900 nm) with a peak external quantum efficiency of 58 % have been achieved with the broad spectral coverage across the visible spectrum. Analysis using an exciton diffusion model shows this efficient carrier generation is mainly due to the large exciton diffusion length of pentacene films. Joint XRD and AFM studies reveal that the highly crystalline nature of pentacene films can account for the observed large exciton diffusion length. In addition, the electrical characteristics are studied as a function of light intensity using the equivalent circuit model used for inorganic pn-junction solar cells. Dependences of equivalent-circuit parameters on light intensity are further investigated using a modified equivalent circuit model, and their effects on the overall photovoltaic performance are discussed.

A series of experiments was carried out to compare the structural and electronic properties of intrinsic nanocrystalline silicon (nc-Si:H) thin films deposited via continuous wave (cw) and pulsed (p)-PECVD at 150°C substrate temperature. Working at this temperature allows for the easy transfer of film recipes from glass to plastic substrates in the future. During the p-PECVD process the pulsing frequency was varied from 0.2 to 50 kHz at 50% duty cycle. Approximately 15% drop in the deposition rate was observed for the samples fabricated in p-PECVD compared to cw-PECVD. The optimum crystallinity and photo (σph) and dark conductivity (σD) were observed at 5 kHz pulsing frequency, with ~10% rise in crystallinity and about twofold rise in the σph and σD compared to cw-PECVD. However, for both the cw and p-PECVD nc-Si:H films, the observed σph and σD were one to two orders and three orders of magnitude higher respectively than those reported in literature. The average activation energy (EA) of 0.16 ∓ 0.01 eV for nc-Si:H films deposited using p-PECVD confirmed the presence of impurities, which led to the observation of the unusually high conductivity values. It was considered that the films were contaminated by the impurity atoms after they were exposed to air. Following the thin film characterization procedure, the optimized nc-Si:H film recipes, from cw and p-PECVD, were used to fabricate the absorber layer of thin film solar cells. The cells were then characterized for J-V and External Quantum Efficiency (EQE) parameters. The cell active layer fabricated from p-PECVD demonstrated higher power conversion efficiency (η) and a maximum EQE of 1.7 ∓ 0.06 % and 54.3% respectively, compared to 1.00 ∓ 0.04 % and 48.6% respectively for cw-PECVD. However, the observed η and EQE of both the cells were lower than a reported nc-Si:H cell fabricated via p-PECVD with similar absorber layer thickness. This was due to the poor Short-circuit Current Density (Jsc), Open-circuit Voltage (Voc), and Fill Factor (FF) of the cw and p-PECVD cells respectively, compared to the reported cell. The low Jsc resulted from the poor photocarrier collection at longer and shorter wavelengths and high series resistance (Rseries). On the other hand, the low Voc stemmed from the low shunt resistance (Rsh). It was inferred that the decrease in the Rsh occurred due to the inadequate electrical isolation of the individual cells and the contact between the n – layer and the front TCO contact at the edge of the p-i-n deposition area. Additionally, the net effect of the high Rseries and the low Rsh led to a decrease in the FF of the cells.

Solar photovoltaic has become one of the potential solutions for current energy needs and for combating greenhouse gas emissions. The photovoltaics (PV) industry is booming, with a yearly growth rate well in excess of 30% over the last decade. This explosive growth has been driven by market development programs to accelerate the deployment of sustainable energy options and rapidly increasing fossil fuel prices. Currently, the PV market is based on silicon wafer solar cells (thick cells of around 150–300 μm made of crystalline silicon). This technology, classified as the first-generation of photovoltaic cells. The second generation of photovoltaic materials is based on the introduction of thin film layers of semiconductor materials. Unfortunately, the conversion efficiency of the current PV systems is low despite the lower manufacturing costs. Nevertheless, to achieve highly efficient silicon solar cell devices, the development of new high quality materials in terms of structure and electrical properties is a must to overcome the issues related to amorphous silicon (a -Si:H) degradation. Meanwhile, to remain competitive with the conventional energy sources, cost must be taken into consideration. Moreover, novel approaches combined with conventional mature silicon solar cell technology can boost the conventional efficiency and break its maximum limits. In our approach, we set to achieve efficient, stable and affordable silicon solar cell devices by focusing on the development of a new device made of epitaxial films. This new device is developed using new epitaxial growth phosphorous and/or boron doped layers at low processing temperature using plasma enhanced chemical vapor deposition (PECVD). The junction between the phosphorous or boron-doped epitaxial film of the device is formed between the film and the p or n-type crystalline silicon (c-Si) substrate, giving rise to (n epi-Si/p c-Si device or p epi-Si/n c-Si device), respectively. Different processing conditions have been fully characterized and deployed for the fabrication of different silicon solar cells architectures. The high quality epitaxial film (up to 400 nm) was used as an emitter for an efficient stable homojunction solar cell. Extensive analysis of the developed fine structure material, using high resolution transmission electron microscope (HRTEM), showed that hydrogen played a crucial role in the epitaxial growth of highly phosphorous doped silicon films. The main processing parameters that influenced the quality of the structure were; radio frequency (RF) power density, the processing chamber pressure, the substrate temperature, the gas flow rate used for deposition of silicon films, and hydrogen dilution. The best result, in terms of structure and electrical properties, was achieved at intermediate hydrogen dilution (HD) regime between 91 and 92% under optimized deposition conditions of the rest of the processing parameters. The conductivity and the carrier mobility values are good indicators of the electrical quality of the silicon (Si) film and can be used to investigate the structural quality indirectly. The electrical conductivity analyses using spreading resistance profile (SRP), through the detection of active carriers inside the developed films, are presented in details for the developed epitaxial film under the optimized processing conditions. Measurements of the active phosphorous dopant revealed that, the film has a very high active carrier concentration of an average of 5.0 x1019 cm-3 with a maximum value of 6.9 x 1019 cm-3 at the interface between substrate and the epitaxial film. The observed higher concentration of electrically active P atoms compared to the total phosphorus concentration indicates that more than half of dopants become incorporated into substitutional positions. Highly doping efficiency ηd of more than 50 % was calculated from both secondary ion mass spectroscopy (SIMS) and SRP analysis. A variety of proposed structures were fabricated and characterized on planar, textured, and under different deposition temperatures. Detailed studies of the photovoltaic properties of the fabricated devices were carried out using epitaxial silicon films. The results of these studies confirmed that the measured open circuit voltage (Voc) of the device ranged between 575 and 580 mV with good fill factor (FF) values in the range of 74-76 %. We applied the rapid thermal process (RTP) for a very short time (60 s) at moderate temperature of 750oC to enhance the photovoltaic properties of the fabricated device. The following results were achieved, the values of Voc, and the short circuit current (Isc) were 598 mV and 27.5 mA respectively, with a fill factor value of up to 76 % leading to an efficiency of 12.5 %. Efficiency enhancement by 13.06 % was achieved over the reference cell which was prepared without using RTP. Another way to increase the efficiency of the fabricated device is to reduce the reflections from its polished substrate. This was achieved by utilizing the light trapping technique that transforms the reflective polished surface into a pyramidical texturing using alkaline solutions. Further enhancements of both Voc and Isc were achieved with values of 612 mV and 31mA respectively, and a fill factor of 76 % leading to an increase in the efficiency by up to 13.8 %. A noticeable efficiency enhancement by ~20 % over the reference cell is reported for the developed devices on the textured surfaces. Moreover, the efficiency of the fabricated epitaxial silicon solar cells can be boosted by the deployment of silicon nanocrystals (Si NCs) on the top surface of the fabricated devices. In the course of this PhD research we found a way to achieve this by depositing a thin layer of Si NCs, embedded in amorphous silicon matrix, on top of the epitaxial film. Structural analysis of the deposited Si NCs was performed. It is shown from the HRTEM analysis that the developed Si NCs, are randomly distributed, have a spherical shape with a radius of approximately 2.5 nm, and are 10-20 nm apart in the amorphous silicon matrix. Based on the size of the developed Si NCs, the optical band gap was found to be in the region of 1.8-2.2 eV. Due to the incorporation of Si NCs layer a noticeable enhancement in the Isc was reported.

The field of organic electronics has become an increasingly important field of research in recent years. Organic based semiconductors have the potential for creating inexpensive, solution processed devices on flexible substrates. Some of the applications of organic semiconductors include organic field effect transistors, organic light emitting diodes and organic photovoltaics. Functionalized pentacenes have been proven to be viable donor materials for use in organic photovoltaic devices. The goal of this research is to synthesize and test the viability of novel electron deficient pentacenes and pentacene based materials as acceptors to be used as drop-in replacements for PCBM in bulk-heterojunction organic solar cells. Our goal was to tune and improve the efficiencies of these solar cells in a two pronged approach. First we tuned the open circuit voltage of these devices by determining the optimal energy levels of these acceptors by varying the number of electron withdrawing substituents on the acene core. We also tuned the short circuit current by chemically altering the solid state packing and optimizing device processing conditions. A preliminary structure-property relationship of these small molecule acceptors and photovoltaic device efficiency was established as a result.

Stable organic semiconductors are critical to produce inexpensive, efficient and flexible thin film organic solar cells. A current chemical focus is the synthesis of stable, electron-accepting materials to be utilized as an acceptor layer in photovoltaics.1 The Anthony group has shown that the functionalization of pentacene with suitable electron withdrawing groups provides a catalog of suitable acceptors for this purpose.2 These pentacenes can be further modified to pack in a unique 1-dimensional "sandwich herringbone" crystal packing, leading to improved device current.3 To improve the stability of acene acceptors, we have taken two hetero-atom themed approaches. First, we have studied the acenequinone as an electron-accepting chromophore.4 Further, we replaced the terminal aromatic rings with heterocycles, such as furan or thiophene. In order to enhance the crystal engineering versatility of the chromophore, we utilize c-fused heterocycles (rather than the more commonly used b-fused cycles seen in e.g. anthradithiophenes). The c-fused acenequinones can be tetra-functionalized with silylethynyl groups to influence crystal packing and increase solubility.5 The silylethyne groups are known to increase the photostability and lower the energy gap (Eg) of pentacenes.5 The functionalization of the silylethyne groups also aids in lowering the lowest unoccupied orbital (LUMO) of acene structures.5

Organische Halbleiter besitzen neue, bemerkenswerte Materialeigenschaften, die sie für die grundlegende Forschung wie auch aktuelle technologische Entwicklung (bsw. org. Leuchtdioden, org. Solarzellen) interessant werden lassen. Aufgrund der starken konformative Freiheit der konjugierten Polymerketten führt die Vielzahl der möglichen Anordnungen und die schwache intermolekulare Wechselwirkung für gewöhnlich zu geringer struktureller Ordnung im Festkörper. Die Morphologie hat gleichzeitig direkten Einfluss auf die elektronische Struktur der organischen Halbleiter, welches sich meistens in einer deutlichen Reduktion der Ladungsträgerbeweglichkeit gegenüber den anorganischen Verwandten zeigt. So stellt die Beweglichkeit der Ladungen im Halbleiter einen der limitierenden Faktoren für die Leistungsfähigkeit bzw. den Wirkungsgrad von funktionellen organischen Bauteilen dar. Im Jahr 2009 wurde ein neues auf Naphthalindiimid und Bithiophen basierendes Dornor/Akzeptor Copolymer vorgestellt [P(NDI2OD‑T2)], welches sich durch seine außergewöhnlich hohe Ladungsträgermobilität auszeichnet. In dieser Arbeit wird die Ladungsträgermobilität in P(NDI2OD‑T2) bestimmt, und der Transport durch eine geringe energetischer Unordnung charakterisiert. Obwohl dieses Material zunächst als amorph beschrieben wurde zeigt eine detaillierte Analyse der optischen Eigenschaften von P(NDI2OD‑T2), dass bereits in Lösung geordnete Vorstufen supramolekularer Strukturen (Aggregate) existieren. Quantenchemische Berechnungen belegen die beobachteten spektralen Änderungen. Mithilfe der NMR-Spektroskopie kann die Bildung der Aggregate unabhängig von optischer Spektroskopie bestätigt werden. Die Analytische Ultrazentrifugation an P(NDI2OD‑T2) Lösungen legt nahe, dass sich die Aggregation innerhalb der einzelnen Ketten unter Reduktion des hydrodynamischen Radius vollzieht. Die Ausbildung supramolekularen Strukturen nimmt auch eine signifikante Rolle bei der Filmbildung ein und verhindert gleichzeitig die Herstellung amorpher P(NDI2OD‑T2) Filme. Durch chemische Modifikation der P(NDI2OD‑T2)-Kette und verschiedener Prozessierungs-Methoden wurde eine Änderung des Kristallinitätsgrades und gleichzeitig der Orientierung der kristallinen Domänen erreicht und mittels Röntgenbeugung quantifiziert. In hochauflösenden Elektronenmikroskopie-Messungen werden die Netzebenen und deren Einbettung in die semikristallinen Strukturen direkt abgebildet. Aus der Kombination der verschiedenen Methoden erschließt sich ein Gesamtbild der Nah- und Fernordnung in P(NDI2OD‑T2). Über die Messung der Elektronenmobilität dieser Schichten wird die Anisotropie des Ladungstransports in den kristallographischen Raumrichtungen von P(NDI2OD‑T2) charakterisiert und die Bedeutung der intramolekularen Wechselwirkung für effizienten Ladungstransport herausgearbeitet. Gleichzeitig wird deutlich, wie die Verwendung von größeren und planaren funktionellen Gruppen zu höheren Ladungsträgermobilitäten führt, welche im Vergleich zu klassischen semikristallinen Polymeren weniger sensitiv auf die strukturelle Unordnung im Film sind. / Organic semiconductors are in the focus of recent research and technological development (eg. for organic light-emitting diodes and solar cells) due to their specific and outstanding material properties. The strong conformational freedom of conjugated polymer chains usually leads to a large number of possible geometric arrangements while weak intermolecular interactions additionally lead to poor structural order in the solid state. At the same time the morphology of those systems has direct influence on the electronic structure of the organic semiconductor which is accompanied by a significant reduction of the charge carrier mobility in contrast to their inorganic counterparts. In that way the transport of charges within the semiconductor represents one of the main limiting factors regarding the performance and efficiency of functional organic devices. In 2009 Facchetti and coworkers presented a novel conjugated donor/acceptor copolymer based on naphthalene diimide and bithiophene [P(NDI2OD‑T2)] which was characterized by an outstanding charge carrier mobility. In this work the mobility of electrons and holes in the bulk of P(NDI2OD‑T2) is determined by single carrier devices and the time-of-flight technique. The results imply a low energetic disorder in these polymer layers. While the material was initially expected to be mainly amorphous, a detailed study of the photophysical properties of P(NDI2OD‑T2) shows that precursors of supramolecular assemblies (aggregates) are already formed in polymer solution. Quantum-chemical calculations support the occurring optical changes. NMR spectroscopy was applied to independently prove the formation of chain aggregates in commonly used organic solvents. The investigation of P(NDI2OD‑T2) solutions by analytical ultracentrifugation implies that aggregation mainly proceeds within single polymer chains by reduction of the hydrodynamic radius. To understand the influence of the chemical structure, pre-aggregation and crystal packing of conventional regioregular P(NDI2OD-T2) on the charge transport, the corresponding regioirregular polymer RI-P(NDI2OD-T2) was synthesized. By combining optical, X-ray, and transmission electron microscopy data, a quantitatively characterization of the aggregation, crystallization, and backbone orientation of all of the polymer films was possible, which was then correlated to the electron mobilities in electron-only diodes. The anisotropy of the charge transport along the different crystallographic directions is demonstrated and how the mobility depends on π-stacking but is insensitive to the degree or coherence of lamellar stacking. The comparison between the regioregular and regioirregular polymers also shows how the use of large planar functional groups leads to improved charge transport, with mobilities that are less affected by chemical and structural disorder with respect to classic semicrystalline polymers such as poly(3-hexylthiophene).

In this thesis, a novel method of reducing the rear surface recombination in copper indium gallium (di) selenide (CIGS) thin film solar cells, using atomic layer deposited (ALD) Al2O3, has been evaluated via qualitative opto-electrical characterization. The idea stems from the silicon (Si) industry, where rear surface passivation layers are used to boost the open-circuit voltage and, hence, the cell efficiency. To enable a qualitative assessment of the passivation effect, Al/Al2O3/CIGS metal-oxide-semiconductor (MOS) devices with 3-50 nm oxide thickness, some post-deposition treated (i.e. annealed), have been fabricated. Room temperature capacitance-voltage (CV) measurements on the MOS devices indicated a negative fixed charge density (Qf) within the Al2O3 layer, resulting in a reduced CIGS surface recombination due to field effect passivation. After annealing the Al2O3 passivation layers, the field effect passivation appeared to increase due to a more negative Qf. After annealing have also indications of a lower density of interface traps been seen, possibly due to a stronger or activated chemical passivation. Additionally, the feasibility of using ALD Al2O3 to passivate the surface of CIGS absorber layers has also been demonstrated by room temperature photoluminescence (PL) measurements, where the PL intensity was about 20 times stronger for a structure passivated with 25 nm Al2O3 compared to an unpassivated structure. The strong PL intensity for all passivated devices suggests that both the chemical and field effect passivation were active, also for the passivated as-deposited CIGS absorbers.

A hole-collecting interlayer layer for organic solar cells, NiO, processed by atomic layer deposition (ALD) was studied. ALD-NiO film offered a novel alternative to efficient hole-collecting interlayers in conventional single-junction organic solar cells. Next, surface modifications with aliphatic amine group containing polymers for use as electron-collecting interlayers were studied. Physisorption of the polymers was found to lead to large reduction of the work function of conducting materials. This approach provides an efficient way to provide air-stable low-work function electrodes for organic solar cells. Highly efficient inverted organic solar cells were demonstrated by using the polymer surface modified electrodes. Lastly, charge recombination layers of the inverted tandem organic solar cells were studied. Efficient charge recombination layers were realized by using the ALD and the polymer surface modification. The charge recombination layer processed by ALD provided enhanced electrical and barrier properties. Furthermore, the polymer surface modification on the charge recombination layers showed large work function contrast, leading to improved inverted tandem organic solar cells. The inverted tandem organic solar cells with the new charge recombination layer showed fill factor over 70% and power conversion efficiency over 8%.

Nanowires are high aspect ratio nanostructures with structural diameters on the order of nanometers to hundreds of nanometers. In this work, the optical properties of highly crystalline silicon nanowires grown by the Vapor-Liquid-Solid (VLS) method surrounded by a thin silicon shell are investigated for thin film solar cell applications. Crystalline core nanowires were surrounded by a conformal amorphous silicon shell and exhibited extremely high absorption of 95% at short wavelengths (??<550nm) and very low absorption of <2% at long wavelengths (??>780nm). Nanowires were disordered with average lengths ranging from 1.3 to 2.3 ??m. The absorption increased at longer wavelengths as a function of amorphous shell radial thickness, significantly higher than the absorption of a reference planar a-Si thin film. In addition, a new method to grow epitaxial silicon at low growth temperatures on glass substrates is demonstrated. Highly crystalline silicon nanowires with an average length of 800 nm were used as the seed crystal to grow an epitaxial silicon shell around, using a low temperature process. The nanowire core was grown at 400??C, and the shell was grown at about 150??C. Such epitaxial grown nanowire shells could be used as a building block for nanotechnology applications in which epitaxial silicon is required over large-area substrates such as glass. Furthermore, the epitaxial silicon shell nanowires exhibited absorption > 90% up to a wavelength of 600 nm, which was significantly higher than that of a planar 1 ??m nanocrystalline silicon film. The high absorption exhibited by nanowires with both amorphous and crystalline silicon shells makes them promising for use in photovoltaic and photodetector applications. Silicon nanowires were incorporated into thin film silicon n-i-p solar cells in two configurations: as a nanostructured back reflector, and in core-shell nanowire solar cells. First, domed-shaped nanostructures were fabricated by coating an array of silicon nanowires with a thick layer of amorphous silicon. After the nanostructures were coated with Ag and ZnO:Al, they were used as the backreflector in an n-i-p amorphous silicon solar cell. The nanostructured backreflector improved light scattering within the solar cell, leading to a short circuit current of 14.8mA/cm2, a 13% improvement over that of the planar device, which had a Jsc=13.1 mA/cm2. The overall conversion efficiency of nanostructured backreflector device was ?? = 8.87%, a strong improvement over that of the planar device (?? = 7.47%). Silicon nanowires were also incorporated into core-shell nanowire solar cells. The first device architecture investigated consisted of nanowires incorporated as the intrinsic absorption layer between a planar n+ layer and conformal p+ layer. However, the fabricated devices exhibited very low collection efficiencies of < 2% due to the presence of impurities incorporated by the catalyst used during nanowire growth. As a result, the device architecture was modified such that the nanowires provided high aspect ratio structure to enhance absorption in a shell material, but the nanowires themselves were not used as an active device component. Nanowire core-amorphous silicon shell solar cells, on average 525 nm long and about 350nm in total diameter, exhibited an impressive low total reflectance of <3% in the wavelength interval of 410 nm < ?? < 640nm and exceeded 10% only for ??>700 nm. As a result, the core-shell nanowire devices exhibited enhancement in quantum efficiency at low wavelengths, ?? < 500nm and high wavelengths, ?? > 600nm as compared to a planar device. The resulting short circuit current was 14.1 mA/cm2 compared to 12.3 mA/cm2 for the planar device, an improvement of ~15%. Nanowire core- nanocrystalline silicon shell solar cells were also fabricated using the same device architecture. Core-shell nanowires with an average length of 800 nm showed significant enhancement in quantum efficiency over all wavelengths as compared to a 1 ??m thick planar solar cell. The core-shell nanowire device had a short-circuit current of 16.2 mA/cm2 , a ~25% improvement over that of the planar thin film solar cell (Jsc=13.0 mA/cm2). Core-shell nanowire devices did, however, have lower open circuit voltage compared to the planar device. Non-conformal coverage was found to be a limiting factor in device performance, but further improvements can be expected with optimization of the n-i-p deposition conditions and nanowire density.

In order to improve the optical losses of spherical silicon solar cells, new fabrication designs were presented. The new device structures are fabricated based on integration of nanostructures into spherical silicon solar cells. These new device structures include: spherical silicon solar cells integrated with nanostructured antireflection coating layers, spherical silicon solar cells with hemispherical nanopit texturing, and cells integrated with colloidal quantum dots. Silicon spheres were characterized by means of transmission electron microscopy (TEM), single-crystal x-ray diffraction and x-ray powder diffraction to establish the crystallinity nature of the silicon spheres. Furthermore, the material properties of silicon spheres including surface morphology, microwave photoconductivity decay lifetime, and impurity elemental distributions were studied. Silicon nitride antireflection coating layers were developed and deposited onto the spherical silicon solar cells, using a PECVD system. A low temperature hydrogenation plasma technique was developed to improve the passivation quality of the spherical silicon solar cells. The spectral response of silicon spheres with and without a silicon nitride antireflection coating was studied. We have successfully developed and integrated a nanostructured antireflection coating layer into spherical silicon solar cells. The nanostructured porous layer consists of graded-size silicon nanocrystals and quantum-size Si nanoparticles embedded in an oxide matrix. This layer has been characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), Scanning tunneling TEM, energy filtered TEM, transmission electron diffraction (TED), electron energy loss spectroscopy (EELS), energy dispersive x-ray (EDX), Raman spectroscopy and photoluminescence spectroscopy (PL). We developed a novel technique of electrochemical etching for silicon surface texturing using a liquid-phase deposition of oxide mask. Using a focus ion-beam (FIB) technique, cross-sectional TEM samples were prepared to investigate the nature of texturing and the composition of the deposited mask. The hemispherical nanopit texturing was successfully integrated into spherical silicon solar cells and the etching mechanisms and the chemical reactions were discussed. CdSe colloidal quantum dots with diameter of about 2.8nm were integrated into a graded-density nanoporous layer. This structure was implemented on the emitter of the spherical silicon solar cells and the spectral response with and without incorporation of QDs was studied.