TL;DR: In this paper, the impact of rapid thermal annealing (RTA) on thin-film polycrystalline silicon (pc-Si) solar cells on glass made by evaporation of amorphous silicon (a-Si), and subsequent solid phase crystallization (SPC), is investigated.
Abstract: In this letter, we investigate the impact of rapid thermal annealing (RTA) on thin-film polycrystalline silicon (pc-Si) solar cells on glass made by evaporation of amorphous silicon (a-Si) and subsequent solid-phase crystallization (SPC). These devices have the potential to deliver low-cost photovoltaic electricity and are named EVA cells (SPC of EVAporated a-Si). The RTA is used to perform a high-temperature (>700°C) process for point defect annealing and dopant activation. RTA processes have predominantly been developed for wafer-based devices yet also have great potential for low-temperature devices such as thin-film pc-Si on glass solar cells. Parameter variations are performed on EVA solar cells to determine optimum values for point defect removal and dopant activation while minimizing dopant diffusion causing junction smearing. The 1-Sun open-circuit voltage, Voc, of the as-crystallized pc-Si devices is rather modest (135mV). However, after RTA and subsequent hydrogen passivation in a rf PECVD plasm...
TL;DR: In this article, a comprehensive investigation reveals three useful approximations to the optical behavior of isotextured silicon solar cells, including front surface reflectance with spherical cap geometry.
Abstract: A comprehensive investigation reveals three useful approximations to the optical behavior of isotextured silicon solar cells. First, we confirm experimentally that front-surface reflectance is accurately modeled with “spherical cap” geometry. Second, we find that light reflected from the surface has a Lambertian distribution. Random upright pyramid texturing results in a less favorable distribution so that, when encapsulated, photogeneration in an isotextured cell approaches 99% of that achieved in an equivalent pyramidally textured device. Third, we perform ray tracing simulations to determine the 1-D photogeneration profile beneath isotexture. On their first pass, rays traverse the substrate at angle θ1 with respect to the macroscopic normal such that they are distributed according to cos(3 θ1/2). This approximation to the ray trajectory establishes, for isotexture, a useful simulation tool that has been available for application to pyramidally textured devices for two decades. This paper is followed by a contribution that investigates recombination at isotextured surfaces, coupling results with optical analyses to model the performance of isotextured solar cells.
25 Apr 2008
TL;DR: In this paper, a method of forming a diffusion region is disclosed, which consists of depositing a nanoparticle ink on a surface of a wafer to form a non-densified thin film, the nanoparticles having set of nanoparticles, wherein at least some of the dopant atoms diffuse into the wafer.
Abstract: A method of forming a diffusion region is disclosed. The method includes depositing a nanoparticle ink on a surface of a wafer to form a non-densified thin film, the nanoparticle ink having set of nanoparticles, wherein at least some nanoparticles of the set of nanoparticles include dopant atoms therein. The method also includes heating the non-densified thin film to a first temperature and for a first time period to remove a solvent from the deposited nanoparticle ink; and heating the non-densified thin film to a second temperature and for a second time period to form a densified thin film, wherein at least some of the dopant atoms diffuse into the wafer to form the diffusion region.
02 Apr 2008
Abstract: A method for forming a contact to a substrate is disclosed. The method includes providing a substrate, the substrate being doped with a first dopant; and diffusing a second dopant into at least a first side of the substrate to form a second dopant region, the first side further including a first side surface area. The method also includes forming a dielectric layer on the first side of the substrate. The method further includes forming a set of composite layer regions on the dielectric layer, wherein each composite layer region of the set of composite layer regions further includes a set of Group IV semiconductor nanoparticles and a set of metal particles. The method also includes heating the set of composite layer regions to a first temperature, wherein at least some composite layer regions of the set of composite layer regions etch through the dielectric layer and form a set of contacts with the second dopant region.
20 Mar 2008
TL;DR: In this paper, a device for generating electricity from solar radiation is disclosed, which includes a wafer doped with a first dopant, the wafer including a front side and a back side, wherein the front-side is configured to be exposed to the solar radiation.
Abstract: A device for generating electricity from solar radiation is disclosed. The device includes a wafer doped with a first dopant, the wafer including a front-side and a back-side, wherein the front-side is configured to be exposed to the solar radiation. The device also includes a fused Group IV nanoparticle thin film deposited on the front-side, wherein the nanoparticle thin film includes a second dopant, wherein the second dopant is a counter dopant. The device further includes a first electrode deposited on the nanoparticle thin film, and a second electrode deposited on the back-side, wherein when solar radiation is applied to the front-side, an electrical current is produced.
TL;DR: This review summarizes the fundamentals behind the optoelectronic properties of perovskite materials, as well as the important approaches to fabricating high-efficiency perovSKite solar cells, and possible next-generation strategies for enhancing the PCE over the Shockley-Queisser limit are discussed.
Abstract: With rapid progress in a power conversion efficiency (PCE) to reach 25%, metal halide perovskite-based solar cells became a game-changer in a photovoltaic performance race. Triggered by the development of the solid-state perovskite solar cell in 2012, intense follow-up research works on structure design, materials chemistry, process engineering, and device physics have contributed to the revolutionary evolution of the solid-state perovskite solar cell to be a strong candidate for a next-generation solar energy harvester. The high efficiency in combination with the low cost of materials and processes are the selling points of this cell over commercial silicon or other organic and inorganic solar cells. The characteristic features of perovskite materials may enable further advancement of the PCE beyond those afforded by the silicon solar cells, toward the Shockley-Queisser limit. This review summarizes the fundamentals behind the optoelectronic properties of perovskite materials, as well as the important approaches to fabricating high-efficiency perovskite solar cells. Furthermore, possible next-generation strategies for enhancing the PCE over the Shockley-Queisser limit are discussed.
TL;DR: In this article, the authors review the dynamic field of crystalline silicon photovoltaics from a device-engineering perspective and give an up-to-date summary of promising recent pathways for further efficiency improvements and cost reduction employing novel carrierselective passivating contact schemes, as well as tandem multi-junction architectures, in particular those that combine silicon absorbers with organic-inorganic perovskite materials.
Abstract: With a global market share of about 90%, crystalline silicon is by far the most important photovoltaic technology today. This article reviews the dynamic field of crystalline silicon photovoltaics from a device-engineering perspective. First, it discusses key factors responsible for the success of the classic dopant-diffused silicon homojunction solar cell. Next it analyzes two archetypal high-efficiency device architectures – the interdigitated back-contact silicon cell and the silicon heterojunction cell – both of which have demonstrated power conversion efficiencies greater than 25%. Last, it gives an up-to-date summary of promising recent pathways for further efficiency improvements and cost reduction employing novel carrier-selective passivating contact schemes, as well as tandem multi-junction architectures, in particular those that combine silicon absorbers with organic–inorganic perovskite materials.
TL;DR: The UCLA team has successfully passivated perovskite film by controlling the film growth with functional polymers as additive, which opens up a new class of chemical additives for improving perovSkite performance and should pave the way toward improving perOVskite solar cells for high efficiency and stability.
Abstract: The solution processing of polycrystalline perovskite films introduces trap states that can adversely affect their optoelectronic properties. Motivated by the use of small-molecule surfactants to improve the optoelectronic performance of perovskites, we demonstrate the use of polymers with coordinating groups to improve the performance of solution-processed semiconductor films. The use of these polymer modifiers results in a marked change in the electronic properties of the films, as measured by both carrier dynamics and overall device performance. The devices grown with the polymer poly(4-vinylpyridine) (PVP) show significantly enhanced power conversion efficiency from 16.9 ± 0.7% to 18.8 ± 0.8% (champion efficiency, 20.2%) from a reverse scan and stabilized champion efficiency from 17.5 to 19.1% [under a bias of 0.94 V and AM (air mass) 1.5-G, 1-sun illumination over 30 min] compared to controls without any passivation. Treating the perovskite film with PVP enables a VOC of up to 1.16 V, which is among the best reported for a CH3NH3PbI3 perovskite solar cell and one of the lowest voltage deficits reported for any perovskite to date. In addition, perovskite solar cells treated with PVP show a long shelf lifetime of up to 90 days (retaining 85% of the initial efficiency) and increased by a factor of more than 20 compared to those without any polymer (degrading to 85% after ~4 days). Our work opens up a new class of chemical additives for improving perovskite performance and should pave the way toward improving perovskite solar cells for high efficiency and stability.
TL;DR: Efficient charge separation and collection at the grain boundaries measured by KPFM and c-AFM in CH3 NH3PbI3 film in a CH3NH3P bI3/TiO2/FTO/glass heterojunction structure is presented, confirming the beneficial roles grain boundaries play in collecting carriers efficiently.
Abstract: The past 2 years have seen the uniquely rapid emergence of a new class of solar cell based on mixed organic-inorganic halide perovskite. Grain boundaries are present in polycrystalline thin film solar cell, and they play an important role that could be benign or detrimental to solar-cell performance. Here we present efficient charge separation and collection at the grain boundaries measured by KPFM and c-AFM in CH3NH3PbI3 film in a CH3NH3PbI3/TiO2/FTO/glass heterojunction structure. We observe the presence of a potential barrier along the grain boundaries under dark conditions and higher photovoltage along the grain boundaries compare to grain interior under the illumination. Also, c-AFM measurement presents higher short-circuit current collection near grain boundaries, confirming the beneficial roles grain boundaries play in collecting carriers efficiently.
29 Jun 2007
TL;DR: In this article, the authors proposed a method for manufacturing a semiconductor device, in which the number of photolithography steps can be reduced, the manufacturing process can be simplified, and manufacturing can be performed with high yield at low cost.
Abstract: An object is to provide a method for manufacturing a semiconductor device, in which the number of photolithography steps can be reduced, the manufacturing process can be simplified, and manufacturing can be performed with high yield at low cost A method for manufacturing a semiconductor device includes the following steps: forming a semiconductor film; irradiating a laser beam by passing the laser beam through a photomask including a shield for shielding the laser beam; subliming a region which has been irradiated with the laser beam through a region in which the shield is not formed in the photomask in the semiconductor film; forming an island-shaped semiconductor film in such a way that a region which is not irradiated with the laser beam is not sublimed because it is a region in which the shield is formed in the photomask; forming a first electrode which is one of a source electrode and a drain electrode and a second electrode which is the other one of the source electrode and the drain electrode; forming a gate insulating film; and forming a gate electrode over the gate insulating film