Organo-metallic halide perovskite solar cells (PSCs) are considered as a promising alternative photovoltaic technology due to the advantages of low-cost solution fabrication capability and high power conversion efficiency (PCE). PSCs can be made using a conventional (n-i-p) structure and an inverted (p-i-n) configuration. PCE of the conventional p-i-n type PSCs is slightly higher than that of the inverted n-i-p type PSCs. However, the TiO2 electron transporting layer adopted in the conventional PSCs is formed at a high sintering temperature of >450 °C. The TiO2 electron transporting layer limits the application of conventional PSCs using flexible substrates that are not compatible with the high processing temperature. The hole extraction layer (HEL) in the inverted p-i-n type PSCs can be prepared by low-temperature solution fabrication processes, which can be adopted for achieving high performance large area flexible solar cells at a low cost. Inverted PSCs with a PCE range from 10 to 20% have been reported over the past few years. In comparison with the progresses of other photovoltaic technologies, the rapid enhancement in PCE of the PSCs offers an attractive option for commercial viability. The aim of this PhD project is to study the origin of the improvement in the performance of solution-processable inverted PSCs. The surface morphological and electronic properties of the HEL are crucial for the growth of the perovskite active layer and hence the performance of the inverted PSCs. Enhancement in short circuit current density (Jsc), reduced loss in open circuit voltage (Voc), improvement in cha Organo-metallic halide perovskite solar cells (PSCs) are considered as a promising alternative photovoltaic technology due to the advantages of low-cost solution fabrication capability and high power conversion efficiency (PCE). PSCs can be made using a conventional (n-i-p) structure and an inverted (p-i-n) configuration. PCE of the conventional p-i-n type PSCs is slightly higher than that of the inverted n-i-p type PSCs. However, the TiO2 electron transporting layer adopted in the conventional PSCs is formed at a high sintering temperature of >450 °C. The TiO2 electron transporting layer limits the application of conventional PSCs using flexible substrates that are not compatible with the high processing temperature. The hole extraction layer (HEL) in the inverted p-i-n type PSCs can be prepared by low-temperature solution fabrication processes, which can be adopted for achieving high performance large area flexible solar cells at a low cost. Inverted PSCs with a PCE range from 10 to 20% have been reported over the past few years. In comparison with the progresses of other photovoltaic technologies, the rapid enhancement in PCE of the PSCs offers an attractive option for commercial viability. The aim of this PhD project is to study the origin of the improvement in the performance of solution-processable inverted PSCs. The surface morphological and electronic properties of the HEL are crucial for the growth of the perovskite active layer and hence the performance of the inverted PSCs. Enhancement in short circuit current density (Jsc), reduced loss in open circuit voltage (Voc), improvement in charge collection efficiency (ηcc) through suppression of charge recombination were investigated systematically via controlled growth of the perovskite active layer in solution-processed inverted PSCs. Poly (3,4-ethylenedioxythiophene): poly (4-styrenesulfonate) (PEDOT:PSS) is one of the widely used solution processable conductive materials for hole transporting in different optoelectronic devices. PEDOT:PSS HEL also is a perfect electron blocking layer due to its high LUMO level. However, it has been reported that PEDOT:PSS HEL is related to the deterioration in the stability of PSCs due to its acidic and hygroscopic nature. Modification of PEDOT:PSS using solvent additives or incorporating metallic oxide nanoparticles for improving the processability and the performance of the inverted PSCs were reported. This work has been focused primary on realizing the controlled growth of perovskite active layer via HEL/perovskite interfacial modification using sodium citrate-treated PEDOT:PSS HEL and WO3-PEDOT:PSS composite HEL. Apart from investigating the properties of the modified PEDOT:PSS HELs, the purpose of the work is to improve the understanding of the effect of modified HEL on the growth of the perovskite layer, revealing the charge recombination processes under different operation conditions, analyzing change extraction probability, and thereby improving the overall performance of the PSCs. PCE of >11.30% was achieved for PSCs with a sodium citrate-modified PEDOT:PSS HEL, which is >20% higher than that of a structurally identical control device having a pristine PEDOT:PSS HEL (9.16%). The incident photon to current efficiency (IPCE) and light intensity-dependent J-V measurements reveal that the use of the sodium citrate-modified PEDOT:PSS HEL helps to boost the performance of the inverted PSCs in two ways: (1) it improves the processability of perovskite active layer on HEL, and (2) it enables to enhance the charge extraction efficiency at the HEL/perovskite interface. The suppression of charge recombination in the PSCs with a modified HEL also was examined using photocurrent-effective voltage (Jph-Veff) and transient photocurrent (TPC) measurements. Morphological and structural properties of the perovskite layers were investigated using the scanning electron microscope (SEM) and X-ray diffraction (XRD) measurements. The results reveal that high quality perovskite active layer on the modified HEL was attained forming complete perovskite phase. The surface electronic properties of the modified PEDOT:PSS and pristine PEDOT:PSS layers were studied using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) measurements. XPS results reveal that treatment of sodium citrate partially removes the PSS unit in the PEDOT:PSS, resulting in an increase in the ratio of PEDOT to PSS from 0.197 for a treated PEDOT:PSS HEL to that of 0.108 for the pristine PEDOT:PSS HEL. UPS measurements also show that there is an observable reduction in the work function of the modified HEL, implying that sodium citrate-modified PEDOT:PSS HEL possesses an improved electron blocking capability, which is beneficial for efficient operation of the inverted PSCs.;The performance enhancement in MAPbI3-based PSCs with a tungsten oxide (WO3)-PEDOT:PSS composite HEL also was analyzed. The uniform composite WO3-PEDOT:PSS HEL was formed on indium tin oxide (ITO) surface by solution fabrication process. The morphological and surface electronic properties of WO3-PEDOT:PSS composite film were examined using AFM, XPS, UPS and Raman Spectroscopy. SEM images reveal that the perovskite films grown on the composite HEL had a full coverage without observable pin holes. XRD results show clearly that no residual of lead iodide phase was observed, suggesting a complete perovskite phase was obtained for the perovskite active layer grown on the composite HEL. The volume ratio of WO3 to PEDOT:PSS of 1:0.25 was optimized for achieving enhanced current density and Voc in the PSCs. It is demonstrated clearly that the use of the WO3-PEDOT:PSS composite HEL helps to improve the charge collection probability through suppression of the charge recombination at the MAPbI3/composite HEL interface. The charge extraction efficiency at the perovskite/PEDOT:PSS and perovskite/composite HEL interfaces were investigated by analyzing the PL quenching efficiency of the MAPbI3 active layer. It is shown that the PL efficiency quenching at the MAPbI3/composite HEL samples is one order of magnitude higher than that measured for the perovskite/pristine PEDOT:PSS sample, suggesting an enhanced hole extraction probability at the MAPbI3/composite HEL interface. The combined effects of improved perovskite crystal growth and enhanced charge extraction capabilities result in the inverted PSCs with a PCE of 12.65%, which is 22% higher than that of a structurally identical control device (10.39%). The use of the WO3-PEDOT:PSS composite HEL also benefits the efficient operation of the PSCs, demonstrated in the stability test, as compared to that of the control cell under the same aging conditions. With the progresses made in improving the performance of MAPbI3-based PSCs, the research was extended to study the performance of efficient PSCs with mixed halide of MA0.7FA0.3Pb (I0.9Br0.1)3. The effect of the annealing temperature on the growth of the mixed MA0.7FA0.3Pb (I0.9Br0.1)3 perovskite active layer was analyzed. It was found that the optimal growth of the mixed perovskite active layer occurred at an annealing temperature of 100°C. UPS results reveal that the ionization potential of 5.76 eV measured for the mixed cation perovskite is lower than that of MAPbI3-based single cation perovskite layer (5.85 eV), while the corresponding electron affinity of the mixed perovskite was 4.28 eV and that for the MAPbI3 layer was 4.18 eV, respectively. The changes in the bandgap and the energy levels of the MA0.7FA0.3Pb (I0.9Br0.1)3 and MAPbI3 active layers were examined using UV-vis absorption spectroscopy and UPS measurements. Compared to the MAPbI3-based control cell, a 23% increase in Jsc, a 15% increase in Voc and an overall 25% increase in PCE for the MA0.7FA0.3Pb (I0.9Br0.1)3 were achieved as compared to that of the MAPbI3-based PSCs. An obvious improvement in charge collection efficiency in MA0.7FA0.3Pb (I0.9Br0.1)3-based PSCs operated at different Veff was clearly manifested by the light intensity dependent J-V characteristic measurements. PL quenching efficiency also shows the charge transfer between MA0.7FA0.3Pb (I0.9Br0.1)3 and PEDOT:PSS HEL is one order of magnitude higher as compare to that in the MAPbI3-based PSCs, suggesting the formation of improved interfacial properties at the MA0.7FA0.3Pb (I0.9Br0.1)3/HEL interface. The impact of incorporating mixed MA0.7FA0.3Pb (I0.9Br0.1)3 perovskite active layer on PCE and the stability of the PSCs was further studied using a combination of TPC measurement and aging test. The stability of MA0.7FA0.3Pb (I0.9Br0.1)3- and MAPbI3-based PSCs with respect to the aging time was monitored for a period of >2 months. The MA0.7FA0.3Pb (I0.9Br0.1)3-based PSCs are more stable compared to the MAPbI3-based PSCs aged under the same conditions. The aging test supports the findings made with the TPC and light intensity dependent J-V measurements. It shows that the improved interfacial quality at the perovskite/HEL and the enhanced charge extraction capability are favorable for efficient and stable operation of MA0.7FA0.3Pb (I0.9Br0.1)3-based PSCs.

This dissertation computationally and analytically investigates ways to model solar cells when the lateral motion of charge carriers and light are relevant. We focus on back-contact perovskite solar cells, and assessing the experimental technique of scanning photocurrent microscopy as a means to investigate them. Solar cells are three-dimensional objects frequently modelled as being one-dimensional. However, for more complex designs of solar cell or if the cell is only point-illuminated, one-dimensional modelling is insufficient. In the first study, some conditions for reducing the complexity of two-dimensional drift-diffusion simulations are investigated for a back-contact perovskite cell. Analytic expressions for the relationship in both the low extraction velocity and high extraction velocity regimes are demonstrated, and the conditions where these approximations break down are investigated. These findings are then applied a point-excited film with an extended electrode, a problem encountered during scanning photocurrent microscopy. We show the current recorded in this case should decay exponentially with the distance between excitation and electrode, with a decay constant that can be related to device parameters. The characteristic equilibration time for the system to reach this current is demonstrated to increase linearly with distance. Between this gradient and the exponent, information about the diffusion and recombination mechanics can be extracted from a variety of systems. Photon recycling is the process in whereby photogenerated carriers recombine to generate light that is absorbed again within the solar cell. In the second section, we apply the findings of the first section to show that experimental results published elsewhere are best explained by photon recycling in methylammonium lead iodide perovskite back-contact solar cells. However we do not have an established theoretical model for long-ranged lateral optical transport in these solar cells. Three models are developed: a bimolecular model for unscattered, coherent transport; a photon diffusion model for frequently scattered, noncoherent light; and a monomolecular, assisted-diffusion model. The modal nature of coherent optical transport is considered and modifications to previous one-dimensional theories are made. The nature of the photon diffusion model is discussed, as are theoretical shortcomings. All three models are then solved numerically and compared to experimental results. The low-scattering photon diffusion models correspond well to the experiment. The third investigation involves the performance of different architectures of back-contact perovskite cells. These cells potentially offer increased current due to less shadowing by front electrodes. We compare them to each other and to traditional vertical structures. It is found that, in terms of internal transport, the back-contact solar cells give less efficient performance than the vertical design. The best of the back-contact cells investigated is a flat interdigitated design. The increase in efficiency from optical factors would have to exceed 10% for the overall efficiency of back-contact cells to be higher than vertical devices. We also develop a model of photon recycling appropriate for short-ranged, bulk 2D transport and demonstrate that in perovskites, it produces little change in power conversion efficiency (and small changes in short-circuit voltage) when compared with the standard drift-diffusion equations with the second-order recombination constant is adjusted.

Philosophiae Doctor - PhD / Research in renewable energy has become a focal point as a solution to the energy crisis. One of renewable forms of energy is solar energy, with the main challenge in the development of the solar cells being the high cost. This has led to the exploration of the use of organic molecules to construct solar cells since it will lead to lowered costs of construction. The focus of this research is on the synthesis and characterisation of the polyaniline derivatives materials and zinc gallate for application in the construction of hybrid solar cells with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an acceptor. The polyaniline (PANi) and doped polyaniline derivatives, polyaniline phenathrene sulfonic acid (PANi-PSA), poly[ortho-methyl aniline] phenanthrene sulfonc acid (POMA-PSA) poly[ortho-methyl aniline] anthracene sulfonc acid (POMA-ASA) were produced via chemical synthetic procedures. The zinc gallate (ZnGa2O4) was also produced using a chemical method. The vibrational and electronic spectra of the polymers and zinc gallate were interrogated independently and dependently. Electronic transitions due to charge defects (polarons and bipolarons) were observed for the polymers that are doped. The PANi was the one with the lowest band gap of 2.4 eV with the POMA-ASA having the widest bandgap of 3.0 eV. The XRD and TEM analysis of the polymers revealed characteristics that show that the PANi has the highest level of crystallinity and the POMA-ASA displayed the least level of crystallinity. The electronic data, XRD, TEM data led to the conclusion that the conductivity of the polymers is decreasing in the following sequence, PANi > PANi-PSA > POMA-PSA > POMA-ASA. The photoluminescence of the polymers alone and with the nanoparticles was investigated in solution and on an ITO coated glass substrate. Photoluminescence was observed for the polymers due to relaxation of the exciton and also from the formation of excimers. The relaxation due to the exciton was observed at higher energy levels, while the one that is as a result of the excimer formation was seen at lower energy levels. Enhancement of the peak due to the excimer was observed when the compound is mixed with the nanoparticles in solution. When the analysis was done on the ITO coated glass substrate, it was found that zinc gallate does not lead to quenching of the emission of the polymers; hence it can not be used as an acceptor in this particular system. The electrochemical behaviour of the polyaniline derivatives was investigated using cyclic voltammetry and electrochemical impedance spectroscopy. Interaction of the polymers with the PCBM (acceptor) was investigated using UV-visible absorption spectroscopy and photoluminescence spectroscopy. It was able to quench the photoluminescence of the polymers. Hence it was used as an acceptor in the construction of the photovoltaic cells. The polymers alone and with the nanoparticles were used in the formation of bulk heterojunction photovoltaic cells with PCBM as an acceptor. The photovoltaic behaviour was investigated and PANi was the one that displayed the highest efficiency.

No description available.

Dye-sensitised solar cells (DSCs) have the potential to be a low cost solar cell candidate due to the relatively low cost of materials and ease of processing. Also, unlike traditional silicon solar cells, DSCs can be lightweight and flexible, and perform well in diffuse sunlight and indoors which make them an extremely attractive prospect. This thesis investigates the time intensive heating stages associated with the fabrication of a DSC which are currently a bottleneck for translating this technology from the laboratory to an industrial scale. In addition some steps associated with the fabrication of a DSC share similarity to other technologies so these methods could be extremely applicable and versatile. Near infrared (NIR) radiative heating was used here to drastically reduce the heating times associated with DSC fabrication steps. NIR heating involves the absorption of NIR photons by the free electrons of an infrared absorbing substrate which releases thermal energy rapidly. NIR radiation has previously been used for the heating of metallic substrates but this is the first time it has been used to heat glass based substrates, which significantly broadens the potential applications of NIR heating. Upon 12.5 s of NIR exposure FTO and ITO coated glass reached significantly high temperatures, temperatures corresponding well to those required for the DSC heating steps. NIR radiation was used to sinter TiO2 working electrodes and thermally platinise counter electrodes on FTO glass in 12.5 s, 144 times faster than the conventional oven heating of 30 minutes. When assembled into DSC devices these electrodes performed identically to their oven equivalents. When combined with a faster dyeing process this enabled the overall laboratory manufacturing time of a DSC to be reduced from 123 min to 5 min with no compromise in efficiency which is an extremely promising step for the viability of DSC commercialisation.

Over the last five years, a dramatic expansion of renewable energy from Photovoltaic (PV) solar cells has been witnessed. This expansion is due in part to wafer based silicon solar cells. Crystalline silicon solar cells currently dominate the PV market because of their low cost per watt of electricity production. In order for silicon solar cells to continue to govern the market, efficiency improvements and cost reductions must be made. This work focuses on both cost reduction and efficiency improvements, for wafer based silicon solar cells. The main aim of the work was to produce a thin monocrystalline wafer based silicon solar cell. A large proportion of the cost of conventional monocrystalline solar cells is related to the use of high purity silicon substrates. By producing a cell that uses less silicon, significant cost savings can be made. Conventional wafering techniques used in industry are reaching their limit for thin wafer production. The method adopted in this work uses a simple silicon exfoliation technique capable of producing ultrathin silicon foils. A fully operational solar cell was fabricated from a 40mum exfoliated silicon foil. The thin wafer based silicon solar cell was more than four times thinner than a commercially produced equivalent. The work investigated a variety of principles related to the exfoliation and the suitability of the technique for thin photovoltaic devices. By using a thin exfoliated substrate, conventional anti-reflective (AR) suppressing processes could prove problematic. Experiments were conducted into finding an alternative technique to match the performance of the conventional AR process. The formation of porous silicon (PSi) on the surface of a silicon substrate was found not only to match the commercial process, but to exceed it. With a porous silicon layer, reflectivity was suppressed to just 6.68%. The technique could be applied to both thin silicon solar cells and conventional thicker wafer based cells. The reflectivity suppressive layer could be fabricated in a single simple processing step. Investigation was also focused upon the top contact for silicon solar cells. As the top of the cell is responsible for current collection and light absorption, large electrical contacts shade the cell resulting in a decrease in efficiency. Silver nanowires (AgNWs) were successfully analysed and deposited onto standard silicon solar cell top contacts as an enhancement coating. Such a coating was found to improve the collection ability of the top contact without causing a significant increase in shading loss. The use of an optimised AgNW coating can increase cell efficiency by as much as 37%.

This research work was undertaken to solve an industrial problem related to roll-to- roll production of dye-sensitised solar cells (DSCs). It is possible to manufacture DSCs in a roll-to-roll production line on a sheet metal such as titanium. However, DSCs produced in such a way are not commercially viable due to the use of expensive titanium metal. Therefore, the intention behind this work was to utilize a cheap sheet metal such as ECCS (electro chrome coated steel) to manufacture DSCs in a roll-to-roll production facility of TATA steel Europe, as this project was funded by them. Unfortunately, ECCS corrodes in the I[-]/I[3-] redox electrolyte present in a DSC therefore, to protect ECCS from the corrosion whilst using it as a DSC substrate was the real challenging task in this research. In order to solve this problem high temperature resistant polyimide based coatings were developed which can be used to coat ECCS substrates whilst maintaining excellent dimensional stability at the DSC processing temperatures. Such coatings were electrically conducting which helped preserve the electrical conductivity of the underlying metallic substrate. Electrically conductive polyimides were developed by simply blending conductive fillers such as carbon materials and titanium nitride. It was initially thought that carbon/polyimide based coatings would be suitable for this application. However, severe interfacial charge recombination and poor reflectivity made carbon/PI coatings inferior compared to the TiN/PI coatings. TiN/PI coatings performed well but poor reflectivity produced low current outputs. Moreover, TiN/PI was found to reduce the catalytic activity of thermally deposited platinum therefore it was not useful as a counter electrode material. As a solution to these problems, TiN and carbon materials based hybrid coatings were developed. Hybrid coatings did perform efficiently in terms of overall PV performance but due to poor reflectivity, such coatings also produced low J[sc] values. However, counter electrodes prepared using hybrid coating demonstrated excellent PV performance with thermally deposited platinum. Furthermore, TCO (transparent conducting oxide) free glass substrates can also be used to manufacture low-cost PV devices when coated with these conductive coatings.

This thesis presents the transport, material characterization, and device applications of photovoltaic polymers used in bulk heterojunction solar cells. These three areas were found to be well correlated. Materials properties affect charge transport behaviors. Charge transport behaviors affect organic photovoltaic (OPV) cell performances. Two typical PV polymers were selected for investigation. They were poly(3-hexylthiophene) (P3HT) and poly[N-9-hepta- decanyl-2,7- carbazole-alt-5,5-(4’,7’-di-2- thienyl-2’,1’,3’- benzothiadiazole)] (PCDTBT). Different charge transport measurement techniques were employed to study how charge carriers move in OPV materials including space-charge-limited current (SCLC) measurement, dark-injection space-charge-limited current (DI-SCLC) measurement, and admittance spectroscopy (AS). For hole transport measurement on P3HT, electron leakages were found in a presumed hole-only device structure resulting in ill-defined DI-SCLC and AS signals. After inserting a thin electron blocking and trapping (EBT) layer between the active layer and the Au cathode, the electron leakages can be significantly suppressed leading to well-defined transport measurement signals. Applying the EBT layer to the polymer:fullerene bulk heterojunction (BHJ) blends, the transport properties can also be studied. Charge transport measurements were carried out at different temperatures for Gaussian Disorder Model (GDM) analysis to extract energetic disorders σ and high-temperature limit mobilities μ_∞. For P3HT BHJ films, σ were found to be much smaller than PCDTBT BHJ films. Within the same polymer system, similar σ were extracted. σ can be correlated to the device parameters such as open-circuit voltage V_OC and fill factor FF. Large σ was found to limit both V_OC and FF. With the experience of transport measurement for PV materials gained, we focused on a common problem of batch-to-batch variations in device performance. Five batches of amorphous polymers PCDTBT were purchased from two vendors. From gel permeation chromatography, bimodal distributions of molecular weight were observed in all five batches of PCDTBT with different fraction of small molecular weight component. The corresponding charge carrier mobilities and device performances drop significantly with the small molecular weight component. From GDM, all five batches of polymers have similar σ. However, μ_∞ for each batch of PCDTBT appear to have significant differences. The differences originate from the variation of charge carrier hopping distances caused by different amounts of the small molecular weight component of PCDTBT. At last, ZnO prepared by low temperature annealing sol gel method was used as functional layers for OPV cells and charge transport measurements. Structural, elemental, energetic, optical, and electrical characterizations were performed to examine the ZnO. The results suggested that the ZnO should be suitable for organic device applications. The applications of the ZnO on inverted OPV cells and charge transport measurements were demonstrated.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017. / The development of solar roads to convert insolation on vast stretches of land to electrical energy, otherwise dedicated solely for transportation, is in its nascent stage. A great potential is seen for PV application with the maturing of solar road technology. Apart from increasing the versatility by smart utilization of land resources, widening the cover of renewable energy generation will lead to a sustainable, secure energy future. A stand-alone solar pathway for public park lighting or area lighting system, completely independent of the power grid, was designed and operated. Public lighting for 65 m stretch of walkway located next to the Electrical, Electronic and Computer Engineering Department building, was chosen as a case study in this study. The case study presented simplified method for sizing, performance evaluation and simulation of a stand-alone solar pathway to power public lighting on the Bellville Campus of the Cape Peninsula University of Technology. Depending on the requirements of the electrical, the quantity and quality of lighting, as well as the required duration of the lighting were calculated. Battery storage capacity, based on the desired autonomy period, and maximum and average daily depth of discharge, were sized. PV array size, based on the type and specifications of PV module, the time of year with the highest average daily lighting load and minimum solar radiation, were selected and measured. Control strategies for battery protection and lighting control conditions were determined, and the control set points were specified. The operating efficiency of solar pathway was evaluated and showed excellent performance compared to the expected with annual average value of the monthly performance ratio and system efficiency. A stand-alone solar pathway system was programmed using MATLAB, in order to size a PV system to the supply public lighting for the walkway. The computer program used, can be applied to any site with different weather conditions.

abstract: Crystalline silicon has a relatively low absorption coefficient, and therefore, in thin silicon solar cells surface texturization plays a vital role in enhancing light absorption. Texturization is needed to increase the path length of light through the active absorbing layer. The most popular choice for surface texturization of crystalline silicon is the anisotropic wet-etching that yields pyramid-like structures. These structures have shown to be both simple to fabricate and efficient in increasing the path length; they outperform most competing surface texture. Recent studies have also shown these pyramid-like structures are not truly square-based 54.7 degree pyramids but have variable base angles and shapes. In addition, their distribution is not regular -- as is often assumed in optical models -- but random. For accurate prediction of performance of silicon solar cells, it is important to investigate the true nature of the surface texture that is achieved using anisotropic wet-etching, and its impact on light trapping. We have used atomic force microscopy (AFM) to characterize the surface topology by obtaining actual height maps that serve as input to ray tracing software. The height map also yields the base angle distribution, which is compared to the base angle distribution obtained by analyzing the angular reflectance distribution measured by spectrophotometer to validate the shape of the structures. Further validation of the measured AFM maps is done by performing pyramid density comparison with SEM micrograph of the texture. Last method employed for validation is Focused Ion Beam (FIB) that is used to mill the long section of pyramids to reveal their profile and so from that the base angle distribution is measured. After that the measured map is modified and the maps are generated keeping the positional randomness (the positions of pyramids) and height of the pyramids the same, but changing their base angles. In the end a ray tracing software is used to compare the actual measured AFM map and also the modified maps using their reflectance, transmittance, angular scattering and most importantly path length enhancement, absorbance and short circuit current with lambertian scatterer. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2014