is much higher than those of the H-terminated silicon surface
and passivated by a native oxidation layer, 27.88 s and 24.70 s
respectively. It is worth mentioning that the samples without passivation
(H-terminated) and that passivated by native oxidation
also perform well, since the minority carrier lifetimes of such samples
are higher than that (21.10 s) treated by the optimal wetting
oxidation technology [23].
The minority carrier lifetime is determined by the surface and
bulk recombination [28], as given in Eq. (1) bellow;
1
m
= 1
b
+
2S
d (1)
where m and b is the measured lifetime and the bulk lifetime
respectively, S is the surface recombination velocity, and d is the
wafer thickness.
To characterize the surface passivation effect, eliminating the
influence from thickness, we have also calculated the S values from
Eq. (1). In our calculations, b = 19 ms is used [28], and the wafer
thicknesses are all assumed to be 500 m. The S values obtained
are 1051, 895 and 603 cm/s, for the native oxidized, H-terminated,
andi a-Sipassivatedsiliconsurfaces, respectively. These results also
demonstrate that the i a-Si passivation method is the best, which
is consistent with the device performances as given below.
3.3. Device performance
The current-voltage characteristics of the planar ultrathin cSi/PEDOT:PSS
solar cells using above passivation technologies are
shown in Fig. 4(a). Apparently, the device using the i a-Si passivation
method possesses the highest short current density Jsc and
open voltage Voc, thus the best performance (PCE = 5.68%).
The average values of Jsc and Voc including standard deviation
from several solar cell devices are listed in Table 1. Firstly, it can
be seen that the Voc of devices passivated by i a-Si is 6.6% and 8.4%
higher than those without passivation and passivated by native oxidation,
respectively. This improvement can be mainly attributed to
the atomic scale rough surface of the deposited i a-Si layer, which
is better for the formation of high quality hetero junction between
the c-Si and the PEDOT:PSS layer. Then, the Jsc of solar cells passivated
by the i a-si is also enhanced by 4.0% and 8.0%, compared
Table 1
Photovoltaic characteristics of Si/PEDOT:PSS solar cells with different passivation.
Passivation Voc (mV) Jsc (mA/cm2) FF (%) (%)
i a-Si 438 ± 7 19.50 ± 0.22 62.12 ± 2.28 5.30 ± 0.21
H-terminated 411 ± 7 18.75 ± 0.17 64.97 ± 2.88 5.01 ± 0.22
Native oxide 404 ± 35 18.06 ± 0.44 64.35 ± 4.15 4.71 ± 0.59
with those without passivation and passivated by native oxidation
layer. The increased Jsc can be directly related to better passivation
of the i a-Si layer.
The passivation effect of different methods can be reflected by
the R-M/T of the photovoltaic devices. The limited current density
is calculated by integrating the incident solar photon flux density
from AM1.5 spectrum in the waveband 300–1100 nm, under
the assumption that the internal quantum efficiency is 100%. The
obtained results for photovoltaic devices of different thickness are
plotted in Fig. 4(b). For the device of 18 m thickness, we have also
calculated the more practical limited current density that excludes
optical losses, which means the part of light being reflected (supporting
information). The obtained current density is 23.5 mA/cm2.
Referring to this value, the R-M/T for devices passivated using the
i a-Si, HF treatment and native oxidation methods are 83.0%, 79.8%
and 76.9%, respectively. The higher value for the device passivated
by an i a-Si layer denotes that this method is an ideal passivation
method for c-Si/PEDOT:PSS solar cells. Besides, all the R-M/T values
for the devices in this study are dramatically higher than those
for the devices with complex light-trapping designs, 51.0% [13].
This demonstrates the remarkable superiority of planar structural
ultrathin solar cells.
4. Conc
is much higher than those of the H-terminated silicon surfaceand passivated by a native oxidation layer, 27.88 s and 24.70 srespectively. It is worth mentioning that the samples without passivation(H-terminated) and that passivated by native oxidationalso perform well, since the minority carrier lifetimes of such samplesare higher than that (21.10 s) treated by the optimal wettingoxidation technology [23].The minority carrier lifetime is determined by the surface andbulk recombination [28], as given in Eq. (1) bellow;1m= 1b+2Sd (1)where m and b is the measured lifetime and the bulk lifetimerespectively, S is the surface recombination velocity, and d is thewafer thickness.To characterize the surface passivation effect, eliminating theinfluence from thickness, we have also calculated the S values fromEq. (1). In our calculations, b = 19 ms is used [28], and the waferthicknesses are all assumed to be 500 m. The S values obtainedare 1051, 895 and 603 cm/s, for the native oxidized, H-terminated,andi a-Sipassivatedsiliconsurfaces, respectively. These results alsodemonstrate that the i a-Si passivation method is the best, whichis consistent with the device performances as given below.3.3. Device performanceThe current-voltage characteristics of the planar ultrathin cSi/PEDOT:PSSsolar cells using above passivation technologies areshown in Fig. 4(a). Apparently, the device using the i a-Si passivationmethod possesses the highest short current density Jsc andopen voltage Voc, thus the best performance (PCE = 5.68%).The average values of Jsc and Voc including standard deviationfrom several solar cell devices are listed in Table 1. Firstly, it canbe seen that the Voc of devices passivated by i a-Si is 6.6% and 8.4%higher than those without passivation and passivated by native oxidation,respectively. This improvement can be mainly attributed tothe atomic scale rough surface of the deposited i a-Si layer, whichis better for the formation of high quality hetero junction betweenthe c-Si and the PEDOT:PSS layer. Then, the Jsc of solar cells passivatedby the i a-si is also enhanced by 4.0% and 8.0%, comparedTable 1Photovoltaic characteristics of Si/PEDOT:PSS solar cells with different passivation.Passivation Voc (mV) Jsc (mA/cm2) FF (%) (%)i a-Si 438 ± 7 19.50 ± 0.22 62.12 ± 2.28 5.30 ± 0.21H-terminated 411 ± 7 18.75 ± 0.17 64.97 ± 2.88 5.01 ± 0.22Native oxide 404 ± 35 18.06 ± 0.44 64.35 ± 4.15 4.71 ± 0.59with those without passivation and passivated by native oxidationlayer. The increased Jsc can be directly related to better passivationof the i a-Si layer.The passivation effect of different methods can be reflected bythe R-M/T of the photovoltaic devices. The limited current densityis calculated by integrating the incident solar photon flux densityfrom AM1.5 spectrum in the waveband 300–1100 nm, underthe assumption that the internal quantum efficiency is 100%. Theobtained results for photovoltaic devices of different thickness areplotted in Fig. 4(b). For the device of 18 m thickness, we have alsocalculated the more practical limited current density that excludesoptical losses, which means the part of light being reflected (supportinginformation). The obtained current density is 23.5 mA/cm2.Referring to this value, the R-M/T for devices passivated using thei a-Si, HF treatment and native oxidation methods are 83.0%, 79.8%and 76.9%, respectively. The higher value for the device passivatedby an i a-Si layer denotes that this method is an ideal passivationmethod for c-Si/PEDOT:PSS solar cells. Besides, all the R-M/T valuesfor the devices in this study are dramatically higher than thosefor the devices with complex light-trapping designs, 51.0% [13].This demonstrates the remarkable superiority of planar structuralultrathin solar cells.4. Conc
การแปล กรุณารอสักครู่..
