Query: Critical Electric Field of InGaN p-i-n Solar Cell

Candidate papers:

abstract: We present a study of electric field effect on the efficiency of GaN/In0.1Ga0.9N p i n solar cells by using the advanced physical models of semiconductor devices (APSYS) simulation program. In this study, the electric field strength and other parameters such as optimum thickness of p type layer and efficiency of GaN/In0.1Ga0.9N p i n solar cells with different i layer thicknesses have been performed. On the basis of simulating results, for a high efficiency solar cell, it is found that the optimum p type layer concentration is above 4x1016 cm 3 and the suitable thickness is between 0.1 to 0.2 mm. For different i layer thickness and p doping concentrations, a critical electric field (Fc) has been found at 100 kV/cm. It is worth to note that when the electric field strength of i layer below Fc value, the solar cell efficiency will dramatically decrease. Thus Fc can be seen as an index for acquiring the quality of solar device.
author_names: Der-Yuh Lin

Chao Yu Chi
title: Critical Electric Field of InGaN p i n Solar Cell
year: 2013

abstract: The photovoltaic characteristics of Ga face GaN/InGaN p i n solar cells are investigated numerically. The severe polarization and barrier effects induced by the GaN/InGaN hetero interfaces are demonstrated to be detrimental for the carrier collection. The conversion efficiency could be degraded to be out of application when the degree of polarization and/or indium composition are high. To efficiently eliminate both critical issues, the solar cell structure with appropriate band engineering is introduced. In the proposed structure, the photovoltaic characteristics not only show high grade performance but also become insensitive to the degree of polarization, even in the situation of high indium composition.
author_names: Jih-Yuan Chang

Shih-Hsun Yen

Yi-An Chang

Yen-Kuang Kuo
title: Simulation of High Efficiency GaN/InGaN p i n Solar Cell With Suppressed Polarization and Barrier Effects
venue: IEEE Journal of Quantum Electronics
year: 2013

abstract: Photons In, Electrons Out: Basic Principles of PV Electrons and Holes in Semiconductors Generation and Recombination Junctions Analysis of the p n Junction Monocrystalline Solar Cells Thin Film Solar Cells Managing Light Over the Limit: Strategies for Higher Efficiency.
author_names: J Roy Nelson
title: The physics of solar cells
year: 2003

abstract: In order to find an upper theoretical limit for the efficiency of p n junction solar energy converters, a limiting efficiency, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of hole electron pairs is radiative as required by the principle of detailed balance. The efficiency is also calculated for the case in which radiative recombination is only a fixed fraction fc of the total recombination, the rest being nonradiative. Efficiencies at the matched loads have been calculated with band gap and fc as parameters, the sun and cell being assumed to be blackbodies with temperatures of 6000degK and 300degK, respectively. The maximum efficiency is found to be 30% for an energy gap of 1.1 ev and fc 1. Actual junctions do not obey the predicted current voltage relationship, and reasons for the difference and its relevance to efficiency are discussed.
author_names: William Shockley

Hans J Queisser
title: Detailed Balance Limit of Efficiency of p n Junction Solar Cells
year: 1961

abstract: The impact of the polarization compensation InGaN interlayer between the heterolayers of Ga face GaN/InGaN p i n solar cells is investigated numerically. Because of the enhancement of carrier collection efficiency, the conversion efficiency is improved markedly, which can be ascribed to both the reduction of the polarization induced electric field in the InGaN absorption layer and the mitigation of potential barriers at heterojunctions. This beneficial effect is more remarkable in situations with higher polarization, such as devices with a lower degree of relaxation or devices with a higher indium composition in the InGaN absorption layer.
author_names: Jih-Yuan Chang

Bo Ting Liou

Han-Wei Lin

Ya-Hsuan Shih

Shu-Hsuan Chang

Yen-Kuang Kuo
title: Numerical investigation on the enhanced carrier collection efficiency of Ga face GaN/InGaN p i n solar cells with polarization compensation interlayers.
venue: Optics letters
year: 2011

abstract: The advantages of a (0001) face GaN/InGaN p i n solar cell with compositional grading configuration between i InGaN/p GaN layers are studied numerically. With the use of the grading layer, the conversion efficiency is markedly promoted due to the reduction of potential barrier height for holes and due to the decrease of polarization. Optimized conversion efficiency is obtained when the thickness of the grading layer increases to a critical value. This critical thickness is strongly influenced by the polarization charges and doping concentration of the grading layer. When the density of the polarization charges is high or the doping concentration is low, a thick grading layer is required to achieve high efficiency.
author_names: Yen-Kuang Kuo

B C Lin

Jih-Yuan Chang

Fangming Chen

H C Kuo
title: Numerical Study of (0001) Face GaN/InGaN p i n Solar Cell With Compositional Grading Configuration
venue: IEEE Photonics Technology Letters
year: 2012

abstract: The influence of piezoelectric polarization on the performance of p on n (0001) face GaN/InGaN p i n solar cells is investigated. Simulation results show that the energy band is tilted into the direction detrimental for carrier collection due to the polarization induced electric field. When the indium composition of InGaN layer increases, this unfavorable effect becomes more serious which, in turn, deteriorates the device performance. This discovery demonstrates that, besides the issue of crystal quality, the problem caused by the polarization effect needs to be overcome for the development of GaN based solar cells.
author_names: Jih-Yuan Chang

Yen-Kuang Kuo
title: Numerical Study on the Influence of Piezoelectric Polarization on the Performance of p on n (0001) Face GaN/InGaN p i n Solar Cells
venue: IEEE Electron Device Letters
year: 2011

abstract: Abstract The solar power conversion efficiency of compositionally graded In x Ga 1 x N solar cells was simulated using a finite element approach. Incorporating a compositionally graded region on the InGaN side of a p GaN/n In x Ga 1 x N heterojunction removes a barrier for hole transport into GaN and increases the cell efficiency. The design also avoids many of the problems found to date in homojunction cells as no p type high In content region is required. Simulations predict 28.9% efficiency for a p GaN/n In x Ga 1 x N/n In 0.5 Ga 0.5 N/p Si/n Si tandem structure using realistic material parameters. The thickness and doping concentration of the graded region was found to substantially affect the performance of the cells.
author_names: Gregory V Brown

Joel W Ager

Wladek Walukiewicz

Junqiao Wu
title: Finite element simulations of compositionally graded InGaN solar cells
year: 2010

abstract: Excitonic solar cells1 including organic, hybrid organic inorganic and dye sensitized cells (DSCs) are promising devices for inexpensive, large scale solar energy conversion. The DSC is currently the most efficient2 and stable3 excitonic photocell. Central to this device is a thick nanoparticle film that provides a large surface area for the adsorption of light harvesting molecules. However, nanoparticle DSCs rely on trap limited diffusion for electron transport, a slow mechanism that can limit device efficiency, especially at longer wavelengths. Here we introduce a version of the dye sensitized cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires. The nanowire anode is synthesized by mild aqueous chemistry and features a surface area up to one fifth as large as a nanoparticle cell. The direct electrical pathways provided by the nanowires ensure the rapid collection of carriers generated throughout the device, and a full Sun efficiency of 1.5% is demonstrated, limited primarily by the surface area of the nanowire array.
author_names: Matt Law

Lori E Greene

Justin C Johnson

Richard J Saykally

Peidong Yang
title: Nanowire dye sensitized solar cells
venue: Nature materials
year: 2005

abstract: A device physics model has been developed for radial p n junction nanorod solar cells, in which densely packed nanorods, each having a p n junction in the radial direction, are oriented with the rod axis parallel to the incident light direction. High aspect ratio (length/diameter) nanorods allow the use of a sufficient thickness of material to obtain good optical absorption while simultaneously providing short collection lengths for excited carriers in a direction normal to the light absorption. The short collection lengths facilitate the efficient collection of photogenerated carriers in materials with low minority carrier diffusion lengths. The modeling indicates that the design of the radial p n junction nanorod device should provide large improvements in efficiency relative to a conventional planar geometry p n junction solar cell, provided that two conditions are satisfied: (1) In a planar solar cell made from the same absorber material, the diffusion length of minority carriers must be too low to allow for extraction of most of the light generated carriers in the absorber thickness needed to obtain full light absorption. (2) The rate of carrier recombination in the depletion region must not be too large (for silicon this means that the carrier lifetimes in the depletion region must be longer than ~10 ns) If only condition (1) is satisfied, the modeling indicates that the radial cell design will offer only modest improvements in efficiency relative to a conventional planar cell design. Application to Si and GaAs nanorod solar cells is also discussed in detail.
author_names: Brendan M Kayes

Harry A Atwater

Nathan S Lewis
title: Comparison of the device physics principles of planar and radial p n junction nanorod solar cells
year: 2005