Page 49 - Special Issue Modern Trends in Scientific Research and Development, Case of Asia

International Journal of Trend in Scientific Research and Development (IJTSRD)
Special Issue on Modern Trends in Scientific Research and Development, Case of Asia
Available Online: www.ijtsrd.com e-ISSN: 2456 – 6470

Hole Transportation in Photocells Based on

Hydrogenated Amorphous Silicon

1
2
Zaynobidinov Sirojidin Zaynobidinovich , Babahodjayev Umar Samsakhodjayevich ,
3
Nabiyev A’zamjon Botirjonovich , Usmanov Muhammadjon Abduhalil o’g’li
4
1 Doctor of Physical and Mathematical Sciences, Academic, Andijan State University, Andijan, Uzbekistan
2 Associate Professor, Candidate of Physical and Mathematical Sciences,
3 Ph.D, Doctor of Philosophy in Physical and Mathematical Sciences.,
2,3 Namangan State University, Namangan, Uzbekistan
4 Teacher of Namangan State University, Namangan, Uzbekistan

ABSTRACT The vidicon target photo-CVC analysis and calculation.
In this manuscript, amorphous hydrogenated silicon films To study the hole transfer mechanism in the photocurrent
were studied by using the photo-CVC vidicon target structures based on a-Si:H, it is necessary to have a
characteristics. In the photo-CVC characteristic, a region is monopolar photocurrent, in which only photo generated
observed that obeys the quadratic law. It is explained that holes are current carriers. We will consider a structure, that
the changes contribution in the a-Si:H dielectric constant is, the vidicon target structure (Fig.1а.), in which all layers
and the hole lifetime depending on the applied voltage for consist of a-Si:H.
obtaining information from this section about the hole
transportation mechanism is too significant. If illumination is produced from the n layer side by light with

λ~400 nm wavelength, then the light is absorbed at the i -
KEYWORDS: amorphous semiconductor, hydrogenated silicon, layer surface and a carriers "reservoir" or a layer enriched
vidicon target, hole traps, traps energy, mobility gap, sticking with holes is formed in this i -layer part.
centers

INTRODUCTION
At present, the photovoltaic devices quality and efficiency,
including solar cells based on amorphous hydrogenated
silicon a-Si:H, cannot sufficiently meet the requirements for
semiconductor photo converters. The solar cells efficiency
based on a-Si:H under standard conditions (AM spectrum 1.5
2
- 1000 W/m ) reached 8-10% [1], and for tandem structures,
calculations show that it is possible to achieve up to 12-15%
and more [2 ].
Fig.1. The vidicon target (a) structure and the vidicon

target ideal photo-CVC (b).
It is known that the photocurrent in solar cells consists of

two components, that is, electron and hole. The difference in When a reverse voltage is applied, only holes are current
the mobility value of these components is very significant
carriers. This phenomenon was discovered when measuring
2
2
(μе=13 сm /W·s and μn=0,67сm /W·s). This means that hole
the photoconductivity by the vidicon method [4].
photocurrent fraction in the photocurrent is insignificant.

It is known from the studies’ results of such photo-volt-
Therefore, in many works to study the transfer mechanism,
ampere characteristics structures that photo-CVC consists of
the electron dependences and hole photoconductivity of a-
several sections [8].
Si:H и a-Si:H(B) samples on temperature and it was found
that in high-quality a-Si:H samples, the electrons
This photo-CVC behavior can be explained as follows:
photoconductivity depends very little on temperature, , and
suppose that at low temperatures the entire space charge is
in lightly boron-doped a-Si:H samples, the holes
formed by photo generated mobile holes in the valence band,
photoconductivity depended on the temperature at which then the transfer phenomena can be represented as follows.
the stationary photoconductivity was measured in planar
Hole traps create deep energy levels, so that the reverse
samples [3].
holes thermal ejection can be neglected, moreover, the traps

are evenly distributed over the volume. The traps
To analyze the solar cells characteristics and find ways to concentration is much higher than the equilibrium holes
further increase their photo conversion efficiency requires a
concentration in the i-layer, which confirms the low value of
detailed fraction study of each current carriers type and to
the dark current. Then, at low voltages, almost all injected
establish their transfer mechanism. photo generated holes are captured by traps, so the hole
This work is devoted to the theoretical study of the current-
concentration in the i-layer depth will not increase. This
voltage characteristic (CVC) of hole photocurrent and shows
position corresponds to the ohmic region in the photo-CVC
the obtaining information possibility from individual photo-
obtained at low temperatures. With increasing voltage, all
CVC sections about hole transfer mechanism.
ID: IJTSRD35835 | Special Issue on Modern Trends in Scientific Research and Development, Case of Asia Page 44