nanostructured solar cells

8/18/2019 nanostructured solar cells

1/4

Nanostructured Dielectric Layer – A New Approach to Design

Nanostructured Solar Cells

Yusi Chen1*

, Yangsen Kang1*

, Yijie Huo1, Dong Liang

2, Jieyang Jia

1, Li Zhao

3,

Jeremy Kim1, Leon Yao

1, Jeremy Bregman

1 and James Harris

1,3,4

1Department of Electrical Engineering, Stanford University, Stanford, CA, 94305, US2Department of Physics, Stanford University, Stanford, CA, 94305, US

3Department of Material Science and Engineering, Stanford University, Stanford, CA, 94305, US

4Department of Applied Physics, Stanford University, Stanford, CA, 94305, US

*These authors contributed equally to this work

Abstract — Nanostructures have been widely used in solar cellsdue to their extraordinary optical management properties.However, due to the poor junction quality and large surfacerecombination velocity, typical nanostructured solar cells are notefficient. Here we demonstrate a new approach to design and

fabricate whole-wafer nanostructures on dielectric layer for solarcell application. The design, simulation, fabrication andcharacterization of nanostructured dielectric layer silicon solarcells are presented. The optical simulation results illustrate thatthe periodic nanostructure array on dielectric materialssuppresses the reflection and enhances the absorption over a widespectral range. Reflection measurements show that reflection canbe suppressed below 10% for a wide range of solar spectrum andincident angle. The current density-voltage (J-V) characterizationshows that the short circuit current is improved by 44%. Ourresults suggest this nanostructured dielectric layer has thepotential to significantly improve solar cell performance andavoid typical problems of defects and surface recombination fornanostructured solar cells, thus providing a new pathwaytowards realizing high-efficiency and low-cost solar cells.

Index Terms — photovoltaics, nanostructures, light trapping

I. I NTRODUCTION

Nanostructures, including nanowires [1-3], nanopyramids

[4-6], nanodomes [7] and nanocones [8-10], have been widely

investigated in solar cells. Such structures have shown very

promising features for effective anti-reflection and light

trapping, which may lead to low cost, high efficiency solar

cells [1-12]. However, despite much effort put into these

structures, how to effectively utilize nanostructures for high

efficiency is still an open question. Compared with traditional

bulk material solar cells [13], nanostructured solar cells [1-12]

show much lower efficiency. In particular, nanostructured Sisolar cells have 3eV bandgap to avoid

absorption in it. On the other hand, low cost dielectric

materials with bandgap >3eV, including silicon nitride (SiNx),

titanium dioxide (TiO2) and aluminum oxide (Al2O3) [15],

have been widely used in solar cell industry for high quality

surface passivation. In this work, we demonstrate the design,

simulation, fabrication and characterization of a

nanostructured dielectric layer using SiNx on a high quality

planar PN junction Si solar cell, which may overcome thechallenges of low PN junction quality and large surface

recombination velocity. We also present the complete process

to form a nanostructured dielectric layer.


2/4

matched layers were used in the z-direction to minimize

unwanted reflections, while boundary conditions in the x- and

y-directions were periodic.

From the simulation result in figure 1, nanostructured SiNx

layer array reduces the reflection from >35% to


3/4

was measured based on the un-metalized area and was verified

by integration of the EQE spectrum. The results are shown in

figure 3(c) for J-V and figure 3(d) for EQE. EQE has been

improved to >80% over a large range of the solar spectrum

from


4/4

[18] B. O. Dabbousi, et al, "Langmuir-Blodgett Manipulation ofSize-Selected Cdse Nanocrystallites," Chemistry of Materials,

vol. 6, pp. 216-219, 1994.

978-1-4799-4398-2/14/$31.00 ©2014 IEEE 2205

nanostructured solar cells

Documents